Density functional theory (DFT) simulations of the oxygen evolution reaction (OER) are considered essential for understanding the limitations of water splitting. Most DFT calculations of the OER use an acidic reaction mechanism and the standard hydrogen electrode (SHE) as reference electrode. However, experimental studies are usually carried out under alkaline conditions using the reversible hydrogen electrode (RHE) as reference electrode. The difference between the conditions in experiment and calculations is then usually taken into account by applying a pH-dependent correction factor to the latter. As, however, the OER reaction mechanisms under acidic and under alkaline conditions are quite different, it is not clear a priori whether a simple correction factor can account for this difference. We derive in this paper step by step the theory to simulate the OER based on the alkaline reaction mechanism and explain the OER process with this mechanism and the RHE as reference electrode. We compare the mechanisms for alkaline and acidic OER catalysis and highlight the roles of the RHE and the SHE. Our detailed analysis validates current OER simulations in the literature and explains the differences in OER calculations with acidic and alkaline mechanisms.

Point defects are ubiquitous in solid-state compounds, dictating many functional properties such as conductivity, catalytic activity and carrier recombination. Over the past decade, the prevalence of metastable defect geometries and their importance to relevant properties has been increasingly recognised. A striking example is split vacancies, where an isolated atomic vacancy transforms to a stoichiometry-conserving complex of two vacancies and an interstitial (V_X $\rightarrow$ [V_X + ${\textrm{X}}_{\textrm{i}}$ + V_X]), which can be accompanied by a dramatic energy lowering and change in behaviour. These species are particularly challenging to identify from computation, due to the ‘non-local’ nature of this reconstruction. Here, I present an approach for the efficient identification of these defects, through tiered screening which combines geometric analysis, electrostatic energies and foundation machine-learned (ML) models. This approach allows the screening of all solid-state compounds in the Materials Project database (including all entries in the ICSD, along with several thousand predicted metastable materials), identifying thousands of low energy split vacancy configurations, hitherto unknown. This study highlights both the potential utility of (foundation) machine-learning potentials, with important caveats, the significant prevalence of split vacancy defects in inorganic solids, and the importance of global optimisation approaches for defect modelling.

Discovery of electrocatalytic materials for high-performance energy conversion and storage applications relies on the adequate characterization of their intrinsic activity, which is currently hindered by the dearth of a protocol for consistent and precise determination of double layer capacitance (C_DL). Herein, we propose a seven-step method that aims to determine C_DL reliably by scan rate-dependent cyclic voltammetry considering aspects that strongly influence the outcome of the analysis, including (a) selection of a suitable measuring window, (b) the uncompensated resistance, (c) optimization of measuring settings, (d) data acquisition, (e) selection of data suitable for analysis, (f) extraction of the desired information, and (g) validation of the results. To illustrate the proposed method, two systems were studied: a resistor–capacitor electric circuit, and a glassy carbon disk in an electrochemical cell. With these studies, it is demonstrated that when any of the mentioned steps of the procedure are neglected, substantial deviations of the results are observed with misestimations as large as 61% in the case of the investigated electrochemical system. Moreover, we propose allometric regression as a more suitable model than linear regression for the determination of C_DL for both the ideal and the non-ideal systems investigated. We stress the importance of assessing the accuracy of not only highly specialized electrochemical methods, but also of those that are well-known and commonly used as it is the case of the voltammetric methods. The procedure proposed herein is not limited to the determination of C_DL, but can be effectively applied to any other analysis that aims to deliver quantitative results via voltammetric methods, which is crucial for the study of kinetic and diffusion phenomena in electrochemical systems.

The market dynamics, and their impact on a future circular economy for lithium-ion batteries (LIB), are presented in this roadmap, with safety as an integral consideration throughout the life cycle. At the point of end-of-life (EOL), there is a range of potential options—remanufacturing, reuse and recycling. Diagnostics play a significant role in evaluating the state-of-health and condition of batteries, and improvements to diagnostic techniques are evaluated. At present, manual disassembly dominates EOL disposal, however, given the volumes of future batteries that are to be anticipated, automated approaches to the dismantling of EOL battery packs will be key. The first stage in recycling after the removal of the cells is the initial cell-breaking or opening step. Approaches to this are reviewed, contrasting shredding and cell disassembly as two alternative approaches. Design for recycling is one approach that could assist in easier disassembly of cells, and new approaches to cell design that could enable the circular economy of LIBs are reviewed. After disassembly, subsequent separation of the black mass is performed before further concentration of components. There are a plethora of alternative approaches for recovering materials; this roadmap sets out the future directions for a range of approaches including pyrometallurgy, hydrometallurgy, short-loop, direct, and the biological recovery of LIB materials. Furthermore, anode, lithium, electrolyte, binder and plastics recovery are considered in order to maximise the proportion of materials recovered, minimise waste and point the way towards zero-waste recycling. The life-cycle implications of a circular economy are discussed considering the overall system of LIB recycling, and also directly investigating the different recycling methods. The legal and regulatory perspectives are also considered. Finally, with a view to the future, approaches for next-generation battery chemistries and recycling are evaluated, identifying gaps for research. This review takes the form of a series of short reviews, with each section written independently by a diverse international authorship of experts on the topic. Collectively, these reviews form a comprehensive picture of the current state of the art in LIB recycling, and how these technologies are expected to develop in the future.

Modern batteries are highly complex devices. The cells contain many components—which in turn all have many variations, both in terms of chemistry and physical properties. A few examples: the active materials making the electrodes are coated on current collectors using solvents, binders and additives; the multicomponent electrolyte, contains salts, solvents, and additives; the electrolyte can also be a solid ceramic, polymer or a glass material; batteries also contain a separator, which can be made of glass fibres, polymeric, ceramic, composite, etc. Moving up in scale all these components are assembled in cells of different formats and geometries, coin cells and Swagelok cells for funamental testing and understanding, and pouch, prismatic and cylindrical cells for application. Given this complexity dictated by so many components and variations, there is no wonder that addressing the crucial issue of true sustainability is an extremely challenging task. How can we make sure that each component is sustainable? How can the performance can be delivered using more sustainable battery components? What actions do we need to take to address battery sustainability properly? How do we actually qualify and quantify the sustainability in the best way possible? And perhaps most importantly; how can we all work—academia and battery industry together—to enable the latter to manufacture more sustainable batteries for a truly cleaner future? This Roadmap assembles views from experts from academia, industry, research institutes, and other organisations on how we could and should achieve a more sustainable battery future. The palette has many colours: it discusses the very definition of a sustainable battery, the need for diversification beyond lithium-ion batteries (LIBs), the importance of sustainability assessments, the threat of scarcity of raw materials and the possible impact on future manufacturing of LIBs, the possibility of more sustainable cells by electrode and electrolyte chemistries as well as manufacturing, the important role of new battery chemistries, the crucial role of AI and automation in the discovery of the truly sustainable batteries of the future and the importance of developimg a circular battery economy.

Increasing concerns regarding the sustainability of lithium sources, due to their limited availability and consequent expected price increase, have raised awareness of the importance of developing alternative energy-storage candidates that can sustain the ever-growing energy demand. Furthermore, limitations on the availability of the transition metals used in the manufacturing of cathode materials, together with questionable mining practices, are driving development towards more sustainable elements. Given the uniformly high abundance and cost-effectiveness of sodium, as well as its very suitable redox potential (close to that of lithium), sodium-ion battery technology offers tremendous potential to be a counterpart to lithium-ion batteries (LIBs) in different application scenarios, such as stationary energy storage and low-cost vehicles. This potential is reflected by the major investments that are being made by industry in a wide variety of markets and in diverse material combinations. Despite the associated advantages of being a drop-in replacement for LIBs, there are remarkable differences in the physicochemical properties between sodium and lithium that give rise to different behaviours, for example, different coordination preferences in compounds, desolvation energies, or solubility of the solid–electrolyte interphase inorganic salt components. This demands a more detailed study of the underlying physical and chemical processes occurring in sodium-ion batteries and allows great scope for groundbreaking advances in the field, from lab-scale to scale-up. This roadmap provides an extensive review by experts in academia and industry of the current state of the art in 2021 and the different research directions and strategies currently underway to improve the performance of sodium-ion batteries. The aim is to provide an opinion with respect to the current challenges and opportunities, from the fundamental properties to the practical applications of this technology.

Electrochemical CO₂ reduction (CO₂R) is an attractive option for storing renewable electricity and for the sustainable production of valuable chemicals and fuels. In this roadmap, we review recent progress in fundamental understanding, catalyst development, and in engineering and scale-up. We discuss the outstanding challenges towards commercialization of electrochemical CO₂R technology: energy efficiencies, selectivities, low current densities, and stability. We highlight the opportunities in establishing rigorous standards for benchmarking performance, advances in in operando characterization, the discovery of new materials towards high value products, the investigation of phenomena across multiple-length scales and the application of data science towards doing so. We hope that this collective perspective sparks new research activities that ultimately bring us a step closer towards establishing a low- or zero-emission carbon cycle.

Electric vehicles (EVs) have a range of components that produce noise vibration harshness (NVH) at different frequencies compared to vehicles with an internal combustion engine. The propagation of random vibration frequencies from the mentioned sources to EV batteries can cause fatigue damage. Therefore, knowledge of the EV battery performance under extreme vibration conditions is important for evaluating the life and sustainability of battery packaging. In this review, we attempt to explain all possible sources of vibrations in EVs, the vibration-based degradation mechanism of lithium-ion batteries (LIBs), and international standards for the vibration testing of batteries. Three important vibration standards have been explained in this study: UN 38.3, IEC 62660-2, and SAE J2380, to compare the degradation of three forms of LIBs (pouch, prismatic, and cylindrical). This review investigated the impact of vibrations on EV batteries by drawing connections between vibration and battery performance, highlighting EV NVH sources, and discussing vibration standards for battery testing. In addition, the effect of vibration on the process of deterioration and the safety concerns of LIB cells are discussed. Finally, this study points out the research gaps that need to be addressed to improve the future performance of EV batteries.

Photovoltaics (PVs) are a critical technology for curbing growing levels of anthropogenic greenhouse gas emissions, and meeting increases in future demand for low-carbon electricity. In order to fulfill ambitions for net-zero carbon dioxide equivalent (CO₂eq) emissions worldwide, the global cumulative capacity of solar PVs must increase by an order of magnitude from 0.9 TW_p in 2021 to 8.5 TW_p by 2050 according to the International Renewable Energy Agency, which is considered to be a highly conservative estimate. In 2020, the Henry Royce Institute brought together the UK PV community to discuss the critical technological and infrastructure challenges that need to be overcome to address the vast challenges in accelerating PV deployment. Herein, we examine the key developments in the global community, especially the progress made in the field since this earlier roadmap, bringing together experts primarily from the UK across the breadth of the PVs community. The focus is both on the challenges in improving the efficiency, stability and levelized cost of electricity of current technologies for utility-scale PVs, as well as the fundamental questions in novel technologies that can have a significant impact on emerging markets, such as indoor PVs, space PVs, and agrivoltaics. We discuss challenges in advanced metrology and computational tools, as well as the growing synergies between PVs and solar fuels, and offer a perspective on the environmental sustainability of the PV industry. Through this roadmap, we emphasize promising pathways forward in both the short- and long-term, and for communities working on technologies across a range of maturity levels to learn from each other.

Electrocatalytic CO₂ reduction reaction (eCO₂RR) for C₂₊ product generation is crucial for advancing clean energy conversion technologies. Cu-based electrocatalysts have long been regarded as the benchmark for producing C₂₊ products by their moderate adsorption energy for key intermediates and strong C–C coupling capabilities. However, limitations such as poor stability and low selectivity have driven the search for non-Cu-based alternatives. In this review, we carefully analyze the recent progress in non-Cu-based electrocatalysts for eCO₂RR. We identify that the CO₂ activation and adsorption behavior of intermediates significantly influence the C–C coupling steps. Considering this foundation, we propose three non-Cu-based electrocatalysts for C₂₊ products: frustrated Lewis acid-base pair catalyst, chiral catalyst, and molecular catalyst. These catalysts show significant potential for C₂₊ products generation and expanding the catalytic landscape beyond Cu-based systems. Finally, we discuss the current challenges and future directions of this emerging field. This review aims to provide a comprehensive overview and valuable insights to guide future research efforts in developing novel electrocatalysts, contributing to the advancement of sustainable energy applications.

Alkali post deposition treatments (PDT) are the standard method to increase the efficiency of Cu(In,Ga)Se₂ solar cells. In this study, the effects of potassium fluoride (KF) PDTs on narrow band gap Cu(In, Ga)Se₂ (CIS) layers are investigated. The CIS layers were grown on substrates such as glass with alkali-barrier/Mo, glass/Mo, and glass/indium-doped tin oxide. It was found that the effect of the PDT depends on the substrates and that there are conditions under which KF-PDT is detrimental to solar cell performance. Time-of-flight secondary ion mass spectrometry measurements revealed limited ion exchange between Na and K, which caused inhibited diffusion of K into the absorber layer. Further opto-electrical characterization indicated increased recombination in the solar cell. Capacitance–voltage–frequency measurements combined with modelling revealed the formation of an interface defect that is limiting the open circuit voltage and reducing the fill factor. Our findings suggest that the lack of K diffusion into the absorber layer promotes the formation of defects at the surface. This study highlights the complex interaction between alkali coming from PDT and the alkali already present in the absorber layer.

Intermediate band solar cells offer a promising avenue to surpass the Shockley–Queisser limit of $\mathrm{\sim} 30 \, \mathrm{\%}$ that constrains conventional single-junction devices, with the potential to approach an efficiency limit of $\mathrm{\sim} 45 \, \mathrm{\%}$ in terrestrial environments by incorporating a metallic band within the valence-conduction gap. Yet, their practical realization is challenged by difficulties in developing suitable intermediate band (IB) materials. Current approaches, which involve adding inclusions or utilizing highly mismatched alloys, often degrade material quality or present significant technological hurdles. A possible solution that remains underexplored, is to identify crystalline materials that inherently possess an IB and fine-tune their properties. In this work, thousands of crystalline chalcogenides are analyzed using a detailed balance model to quantitatively evaluate their expected efficacy as IB materials. Notably, orthorhombic $\mathrm{VB}_{1} \mathrm{VIA}_{2}$ and $\mathrm{IA}_{4} \mathrm{VIA}_{6}$ compounds, such as $\mathrm{Ta}_{1} \mathrm{Se}_{2}$ and $\mathrm{Cs}_{4} \mathrm{S}_{6}$, are projected to achieve maximum efficiencies exceeding 35%, that is, surpassing the Shockley–Queisser limit. The interplay of IB filling and chemical substitution on the properties of these systems is analyzed, to unravel the impact on performance. This study not only identifies new material candidates for IB solar cells, but also provides insights into efficiency-property relations, hence advancing the understanding of these systems.

The relentless quest for sustainable and eco-friendly energy sources can be addressed through solar cells which convert solar energy to electrical energy. In the family of solar cells, perovskite solar cells (PSCs) have seen an astonishing growth in power conversion efficiency (PCE) to which homojunction perovskite is the newest addition. Although numerous studies have examined PCE enhancement through energy band-offset optimization in the intrinsic PSCs, to date, such a study has never been reported in a homojunction configuration. Considering the enormous potential of homojunction PSCs and the importance of band offset, here we numerically identified the optimized range of conduction and valance band offset (CBO and VBO) in conjunction with donor and acceptor density inside the perovskite layer to boost their photovoltaic efficiency. The effect of the CBO and donor density is found to be superior to the VBO and acceptor density. Unlike intrinsic PSCs, the cliff in the energy band diagram drastically reduces the PCE for the CBO. The optimum CBO and donor density are around 0 to +0.1 eV and 2 × 10¹⁷ cm⁻³ respectively. The PCE is higher and nearly constant for a VBO > 0 eV and acceptor density > 7 × 10¹⁷ cm⁻³. With the optimum values of doping density and band offsets, the maximum PCE is calculated to be 25.43% in the presence of all possible losses and an optimum perovskite thickness of 600 nm with a 30:70% ratio of n and p-doped segments.

The increasing demand for autonomous, low-power devices in the Internet of Things has highlighted the need for efficient indoor photovoltaic (IPV) solutions. While conventional photovoltaics (PVs) are optimized for outdoor conditions, indoor environments present distinct challenges due to spectral variability and lower irradiance. This work establishes quantitative guidelines for designing efficient and injection-resilient inorganic thin-film PV converters for indoor applications. We analyze three key factors that significantly influence IPV performance: (i) bandgap-to-spectrum matching, demonstrating that a bandgap range of 1.6–1.9 eV is optimal for indoor lighting conditions with minimal sensitivity to correlated color temperature variations, (ii) parasitic absorption losses, emphasizing the impact of charge transport layers, particularly CdS, on reducing efficiency under indoor spectra; and (iii) shunt current losses, revealing that shunt pathways become dominant loss mechanisms at low injection levels, necessitating increased shunt resistance for optimized performance. Additionally, we advocate for standardized reporting of key performance metrics, including incident spectra, external quantum efficiency and shunt-related losses, to facilitate reproducibility and meaningful cross-study comparisons. Our work provides a framework for the practical development of IPV devices through the transparent sharing of the tools developed in this study.

Due to climate change, the need for efficient heat pumps is crucial. Magnetocaloric heat pumps are one of these potentially more efficient candidates. Magnetocaloric heat pumps use solid state refrigerants that exhibit a temperature change when a magnetic field change is applied to them. However, current prototype systems are still too expensive for commercial use, due to the need for large permanent magnets. By improving power density, the size of the magnets and therefore the cost can be reduced. To this date the highest power density was achieved by Maier et al (2020 Commun. Phys.3 1–6) using the novel magnetocaloric heat pipe concept. In this work we improve on the design by building magnetocaloric heat pipe consisting of seven segments connected by check valves. Both ethanol and methanol were tested as the heat transfer fluids. Using 154 g of Gadolinium temperature differences of up to 11.5 K and cooling powers of 128 W were achieved. This is a significant step forward in both maximum cooling power as well as temperature difference compared to previous devices of this kind. An extraordinarily large working frequency of 14 Hz was achieved for this device, leading to a very high power density with a specific refrigerant capacity $sRCP$ of 15 W kg⁻¹. In this work we also propose a simple lumped parameter model, which can predict the system performance and allows for further optimization of caloric heat pipes.

Electrocatalytic CO₂ reduction reaction (eCO₂RR) for C₂₊ product generation is crucial for advancing clean energy conversion technologies. Cu-based electrocatalysts have long been regarded as the benchmark for producing C₂₊ products by their moderate adsorption energy for key intermediates and strong C–C coupling capabilities. However, limitations such as poor stability and low selectivity have driven the search for non-Cu-based alternatives. In this review, we carefully analyze the recent progress in non-Cu-based electrocatalysts for eCO₂RR. We identify that the CO₂ activation and adsorption behavior of intermediates significantly influence the C–C coupling steps. Considering this foundation, we propose three non-Cu-based electrocatalysts for C₂₊ products: frustrated Lewis acid-base pair catalyst, chiral catalyst, and molecular catalyst. These catalysts show significant potential for C₂₊ products generation and expanding the catalytic landscape beyond Cu-based systems. Finally, we discuss the current challenges and future directions of this emerging field. This review aims to provide a comprehensive overview and valuable insights to guide future research efforts in developing novel electrocatalysts, contributing to the advancement of sustainable energy applications.

Polymer electrolyte membrane water electrolyzers (PEMWEs) are an important fixture in the generation of green hydrogen. This paper studies the emerging trends in degradation modeling of PEMWEs. The ability to predict durability and degradation in PEMWEs is key to optimizing their control, design, maintenance, safety monitoring, performance, and lifespan. For the purposes of fault detection, bond graph modeling is a novel approach allowing for precise, expandable monitoring and isolation. Future fault detection work should evaluate the system health by considering elevated degradation rates, as unchecked voltage rise can reduce the useful lifetime of PEMWEs. Performance modeling techniques, such as overvoltage fitting and equivalent circuit models, are commonly employed for diagnostics in cell durability experiments, but both suffer when comparing polarization and electrochemical impedance spectroscopy data. They offer indications of the degradation source but must otherwise be complemented by destructive analyses. Moreover, multi-physics and kinetic modeling are growing trends that seek to explain the dissolution of the ionomer content or catalyst material in membrane electrode assemblies. They have been used to a limited extent in diagnostics studies to explain the differences between the durability of different membranes, but are more notable in prognostics studies. Most recently, artificial intelligence and machine learning techniques—which are increasing rapidly in complexity and robustness—have been used to predict cell performance, adjust residual thresholds in monitoring studies, and increase sensor redundancy in cases of non-critical faults. Control techniques and techno-economic analyses have additionally benefited from the consideration of degradation, although in these fields the models employed have been rudimentary. Considerable progress has been made in modeling PEMWE degradation, but there is still work to be done to understand the impact of dynamic performance, predict long-term performance loss, and bridge the gap between model electrode studies and real-world membrane electrode assemblies.

The growing global energy demand and environmental issues associated with fossil fuels highlight the need for sustainable alternatives and among which solar energy plays a key role. Perovskite solar cells (PSCs) are rapidly developing and being considered as a disruptive photovoltaic technology. Particularly PSCs can be made flexible, which offer advantages such as being lightweight and highly adaptable, making them suitable for a wider range of applications. However, flexible solar cells face the dual challenges of insufficient flexibility and lower power conversion efficiency (PCE) compared to their rigid counterparts. Cross-linking polymerization is considered a promising approach to simultaneously improve both the flexibility and PCE of solar cells. Therefore, this study primarily focuses on summarizing the application of cross-linked polymers in flexible PSCs. By categorizing and reviewing the utilization of cross-linked polymers, the goal is to provide readers with a comprehensive understanding of how this technology effectively enhances the flexibility of height performance PSCs.

The growing interest in indoor photovoltaics (IPVs) aligns with the digital technology shift towards an advanced era that integrates widely with the Internet of Things (IoT). IPVs present a promising solution for powering IoT devices by harnessing photonic energy from indoor, low-light environments. Among these, perovskite solar cells have achieved an impressive power conversion efficiency of 27.0% under outdoor light and above 40% under indoor conditions, positioning them as potential energy sources for self-sustaining IoT systems. This review highlights recent advances in perovskite IPVs (PIPVs), particularly for their applications under dim, low-light conditions. It begins by addressing critical challenges that may limit the efficiencies of PIPVs, followed by an in-depth discussion of essential factors for commercial viability, including scalable fabrication, flexibility, stability, and toxicity. Finally, new strategies and future directions are introduced to enhance perovskite and interfacial materials specifically tailored for indoor use. The rapid development of PIPVs holds promise for creating low-cost, high-performance photonic energy harvesters for IoT applications, potentially reducing reliance on traditional batteries and promoting sustainability.

Over the last few years, keen interest has been taken in creating and tuning the concentration of oxygen vacancies in electrode materials to enhance their performance and to develop next-generation rechargeable batteries. Oxygen vacancies can be created in electrode materials by using various synthesis techniques. Furthermore, controlled generation of oxygen vacancies in electrode materials plays an essential role in enhancing their electrochemical properties. However, controlled creation of oxygen vacancies in electrode materials via facile techniques is still a challenge. Furthermore, the characterization techniques available to quantify the exact amount and type of oxygen vacancies present in the bulk as well as the surface of a material are not appropriate. Hence, in this review, we have comprehensively summarized the recent reports on oxygen vacancy-based electrode materials and their impact on the electrochemical performance of rechargeable batteries. Furthermore, the challenges and prospects of these oxygen vacancy-rich electrode materials are also discussed.

Recently, ternary chalcogenide AgBiS2 (ABS) gained enormous attention as it is considered an eco-friendly, non-toxic, and cost-effective alternative as a photo-absorber for photovoltaics (PVs) owing to its excellent optoelectronic properties, i.e., a high absorption coefficient (>105 cm^-1), tunable bandgap, and environmental stability. Unlike CuInGa(S,Se)2 (CIGSSe), perovskites, and other materials, the ultrathin layer of AgBiS2 thickness is about 35 nm, enough to absorb a significant portion of the solar spectrum, making it advantageous for PVs. However, the power conversion efficiency (PCE) of AgBiS2 thin film solar cells (TFSCs) has been reported to be around ~11% lower than that of CIGSSe (23.35%). This review highlights the latest strategies for further advancement in the performance of AgBiS2 TFSCs, mainly focusing on the intrinsic properties of AgBiS2, absorber synthesis methods, device fabrication techniques, challenges, and prospects. Herein, innovative strategies, such as device design, bandgap engineering, doping, surface/interface passivation, and integrating mesoporous layers, are reviewed. Furthermore, the review outlines a roadmap for developing high-efficiency and commercially viable AgBiS2-based PVs for a next-generation sustainable future.

Achieving large-scale production of clean hydrogen, which emits zero local-carbon emissions when powered by renewables, is a prerequisite to advance the hydrogen economy and to delay the escalating global temperatures. While proton-exchange-membrane water electrolyzers (PEMWE) are projected to play a vital role for the market, the technology still encounters challenges associated with cost and scale-up. One viable approach is to reduce the amount of platinum-group-metal (PGM) usage in the PEMWE. Recent studies have introduced novel electrodes designs that eliminate ionomer layers (polymeric layers that conduct protons), while maintaining high performance at low iridium loadings. These ionomer-free electrode designs not only feature high performance, but also enable facile fabrication processes and reuse of iridium after long-term operation, significantly contributing to cost reductions. This paper provides a comprehensive review on the ionomer-free electrodes for PEMWE, exploring its benefits, operation principles, and designs that have been studied in the literature to enhance catalytic activity and prolong durability.

The rising levels of atmospheric CO₂ is a major reason of global warming. CO₂ capture and its conversion into value added chemicals are potential solutions to mitigate this critical issue. This review highlights recent advancements in CO₂ capture methods with approaches for CO₂ reduction to methanol, such as electrocatalysis (EC), photoelectrocatalysis (PEC), and photocatalysis (PC) processes. Special emphasis is placed on catalyst design, system integration, and scalability, as well as the role of interfaces and structural engineering of catalysts in enhancing selectivity, stability, and scalability in EC, PEC, and PC systems. This comprehensive review insights of pathways into future direction and emerging opportunities in CO₂ capture and conversion.

The escalating pressure to mitigate CO₂ emissions calls for novel approaches to produce sustainable fuels and chemicals, as means to close the anthropogenic cycle. This study fulfills a critical need in this field, through the development of modeling tools capable of guiding groundbreaking technical advances in liquid-phase electrochemical CO₂ reduction (ECR). 
An unprecedented 3D model for porous cathodes was designed for the co-electrolysis of CO₂ and water to produce syngas, particularly considering aqueous and ionic liquid (IL) electrolytes to increase CO₂ solubility in the electrolyte while lowering its density and kinematic viscosity to boost ECR process performance. The structural parameters of the cathode, i.e. porosity and pores geometry, were investigated, together with the effects of operational parameters such as type of electrolyte, flow rate, temperature and pressure.
A key outcome was the demonstration of a flow electrolytic system, coupled with an improved porous zinc cathode, capable of producing CO partial current densities of 231 mA/cm² at -1.1 V vs. RHE, with a composition suitable for up-stream methane production (H₂:CO ratio of 3:1), at 10 bar, 45 ºC, and 10 mL/min, reaching the threshold for industrial-relevant yields. Such results show that the combination of tailored IL-based electrolytes and advanced cathode design enables to greatly overcome mass transport limitations and improve reaction dynamics. These results open a new path towards the use of computational smart-search methods to improve the industrial implementation of ECR in liquid-phase.