Anion exchange membrane water electrolysis (AEMWE) offers a green hydrogen production method that eliminates the need for platinum group metals (PGM) as electrocatalysts. This study employs a COMSOL® 6.0 model to simulate a 1×1 cmNi fibre Raney® Ni X37-50RT NiFeO SS316L fibre AEMWE membrane electrode assembly (MEA). The membrane is set at a thickness of , while the anodic and cathodic porous transport layers (PTL) are modelled with a thickness of , each having an average porosity of 0.70. The halfcell overpotentials are experimentally measured to validate the halfcell model in a threeelectrode setup consisting of (working electrode) AGAR-Ag/AgCl Ptwire (counter electrode). Two freshly prepared MEAs validated the (i) base case and (ii) sensitivity analysis models. The base case model validated the MEA results at 20 °C and 1 atm in 1M KOH electrolyte feed at 1.56 ml min−1 cm−2. The five parameters studied with the sensitivity analysis revealed the most influential parameters based on area-specific resistance (ASR) change in the following order (＋ and indicate increase and decrease in ASR, respectively): KOH concentration (97%), membrane thickness (＋ 9%), temperature (4%), cathode feed type (0.5%), and KOH flow rate (0.5%).

Anion exchange membrane water electrolyzer (AEMWE) is a rising technology that offers potential advantages in cost and scalability over proton exchange membrane water electrolyzer (PEMWE) technology. However, AEMWEs that stably operate in pure water still employ platinum-group-metal (PGM) catalysts, especially at the cathode. Here, by using an appropriate ionomer at both the anode and cathode, as well as a new hydrogen evolution reaction (HER) catalyst, we achieve sustained pure-water AEM water electrolysis using only PGM-free electrocatalysts. Our optimized AEMWE can operate stably for more than 550 h at 1 A/cm2 with a cell voltage of 1.82 V. This performance competes favorably over the state-of-the-art, PGM-containing, AEMWEs. Unexpectedly, we find that the cathode performance is the bottleneck in pure-water AEMWE. The application of a cathode ionomer can lower the cell voltage by up to 1.4 V at 1 A/cm2. Our work reveals the importance of ionomers for pure-water AEMWEs and identifies cathode improvement as a key area for future work.

Hydrogen production by direct seawater electrolysis is an alternative technology to conventional freshwater electrolysis, mainly owing to the vast abundance of seawater reserves on earth. However, the lack of robust, active, and selective electrocatalysts that can withstand the harsh and corrosive saline conditions of seawater greatly hinders its industrial viability. Herein, a series of amorphous transition-metal phospho-borides, namely Co-P-B, Ni-P-B, and Fe-P-B are prepared by simple chemical reduction method and screened for overall alkaline seawater electrolysis. Co-P-B is found to be the best of the lot, requiring low overpotentials of ≈270 mV for hydrogen evolution reaction (HER), ≈410 mV for oxygen evolution reaction (OER), and an overall voltage of 2.50 V to reach a current density of 2 A cm⁻² in highly alkaline natural seawater. Furthermore, the optimized electrocatalyst shows formidable stability after 10,000 cycles and 30 h of chronoamperometric measurements in alkaline natural seawater without any chlorine evolution, even at higher current densities. A detailed understanding of not only HER and OER but also chlorine evolution reaction (ClER) on the Co-P-B surface is obtained by computational analysis, which also sheds light on the selectivity and stability of the catalyst at high current densities.

The electrochemical conversion of 5-Hydroxymethylfurfural, especially its reduction, is an attractive green production pathway for carbonaceous e-chemicals. We demonstrate the reduction of 5-Hydroxymethylfurfural to 5-Methylfurfurylalcohol under strongly alkaline reaction environments over oxide-derived Cu bimetallic electrocatalysts. We investigate whether and how the surface catalysis of the MOx phases tune the catalytic selectivity of oxide-derived Cu with respect to the 2-electron hydrogenation to 2.5-Bishydroxymethylfuran and the (2 + 2)-electron hydrogenation/hydrogenolysis to 5-Methylfurfurylalcohol. We provide evidence for a kinetic competition between the evolution of H2 and the 2-electron hydrogenolysis of 2.5-Bishydroxymethylfuran to 5-Methylfurfurylalcohol and discuss its mechanistic implications. Finally, we demonstrate that the ability to conduct 5-Hydroxymethylfurfural reduction to 5-Methylfurfurylalcohol in alkaline conditions over oxide-derived Cu/MOx Cu foam electrodes enable an efficiently operating alkaline exchange membranes electrolyzer, in which the cathodic 5-Hydroxymethylfurfural valorization is coupled to either alkaline oxygen evolution anode or to oxidative 5-Hydroxymethylfurfural valorization.

Anion exchange membrane water electrolysis (AEMWE) is an attractive emerging green hydrogen technology. However, the scaling of trends in activity of anode catalysts for the oxygen evolution reaction (OER) from a liquid-electrolyte, three-electrode environment to the two-electrode single-cell format has remained poorly considered. Herein, we critically investigate the scaling of kinetic and catalytic properties of a family of highly active Ni foam (NF) supported, anion (A–)-tuned NiFe(-A–)-OER catalysts. Trends in catalytic activity suggest impressive improvements of up to 91-fold in three-electrode setups (3LC) compared to uncoated NF. While we demonstrate the successful qualitative structure–performance tunability in a 5 cm2 AEMWE single cell, we also find serious limitations in the quantitative predictability of three-electrode setups for single-cell performance trends. Cell environments appear to equalize the cell performances of designer catalysts, which has important ramifications for electrode development. We succeed in analyzing and discussing some of these translation limitations in terms of previously overlooked effects summarized in the activity improvement factor f.

Determination of the electrochemically active surface area (ECSA) is essential in electrocatalysis to provide surface normalized intrinsic catalytic activity. Conventionally, ECSAs of metal oxides and hydroxides are estimated using double layer capacitance (Cdl) measured at nonfaradaic potential windows. However, in the case of Ni-based hydroxide catalysts for the oxygen evolution reaction (OER), the nonfaradaic potential region before the Ni(II) oxidation peak is nonconductive, which hinders accurate electrochemical measurements. To overcome this problem, in this work, we have investigated the use of electrochemical impedance spectroscopy (EIS) at reactive OER potentials to extract the capacitance that is hypothesized to arise due to reactive OER intermediates (O*, OH*, OOH*) adsorbed on the catalyst surface. This allowed the estimation of ECSA and intrinsic activity of NiFe layered double hydroxide (NiFe LDH), the most active, state-of-the-art OER electrocatalyst in alkaline media. We analyzed the OER adsorbates capacitance (Ca) on NiFe LDH and Ni(OH)2 at different electrode potentials and identified a suitable potential range for accurate ECSA evaluation. Finally, we validated our method and the choice of potential range through rigorous catalyst loading and support studies.

Layered double hydroxides (LDHs) are promising catalysts for the oxygen evolution reaction (OER) given their modular chemistry and ease of synthesis. Herein, we report a facile strategy for inclusion of oxygen vacancies (VO) using Ce as a promoter in Co–Ni LDHs that significantly enhances the activity for OER. In situ X-ray absorption spectroscopy (XAS) uncovers an increase in octahedral Co sites and VO upon addition of Ce that promotes the transformation of the LDH into an oxyhydroxide-reactive phase more readily. The presence of an OER-active oxyhydroxide phase along with the generation of VO facilitated by the partial reduction of Ce4+ to Ce3+ under oxidizing conditions results in a better electrochemical activity of Ce-doped electrocatalysts. Density functional theory calculations further corroborate the in situ XAS experimental findings by showcasing that the presence of both Ce and VO reduces the free-energy barrier of the rate-limiting OH* deprotonation step during OER. This work showcases how an enhanced understanding of the role of VO promoters in LDH electrocatalysts can provide insights for future catalyst design in anodic reactions.

Exploring an active and cost-effective electrocatalyst alternative to carbon-supported platinum nanoparticles for alkaline hydrogen evolution reaction (HER) have remained elusive to date. Here, we report a catalyst based on platinum single atoms (SAs) doped into the hetero-interfaced Ru/RuO2 support (referred to as Pt-Ru/RuO2), which features a low HER overpotential, an excellent stability and a distinctly enhanced cost-based activity compared to commercial Pt/C and Ru/C in 1 M KOH. Advanced physico-chemical characterizations disclose that the sluggish water dissociation is accelerated by RuO2 while Pt SAs and the metallic Ru facilitate the subsequent H* combination. Theoretical calculations correlate with the experimental findings. Furthermore, Pt-Ru/RuO2 only requires 1.90 V to reach 1 A cm−2 and delivers a high price activity in the anion exchange membrane water electrolyzer, outperforming the benchmark Pt/C. This research offers a feasible guidance for developing the noble metal-based catalysts with high performance and low cost toward practical H2 production.