Immobilizing Low‐Cost Metal Nitrides in Electrochemically Reconstructed Platinum Group Metal (PGM)‐Free Oxy‐(Hydroxides) Surface for Exceptional OER Kinetics in Anion Exchange Membrane Water Electrolysis

Abstract

A highly efficient and platinum group metal (PGM)‐free oxygen evolution reaction (OER) electrode is developed by immobilizing Ni3N particles on the electrochemically reconstructed amorphous oxy‐hydroxides surface, resulting in a twofold higher industrial relevance current density of 1 A cmgeo−2 at an ultra‐small overpotential η(O2) of 271 mV, with a high turnover frequency of 2.53 s−1, high Faradic efficiency of 99.6 % and exceptional OER stability of 1000 h in continuous electrolysis. Such a unique amorphous‐crystalline interface with enriched active sites greatly facilitates electron transport and OER kinetics at the electrode‐electrolyte interface. Further, combined with an efficient PGM‐free cathode (MoNi4/MoO2@Ni), this electrode demonstrates a current density of 685 mA cmgeo−2 at 1.85 Vcell at 70 °C in an anion exchange membrane water electrolyzer (AEMWE) operated with ultra‐pure water‐electrolyte. These findings highlight the design of highly‐efficient oxygen‐evolving catalysts and significant advancement in the practical implementation of AEMWEs for grid‐scale hydrogen production.

In-Situ Ionomer-Free Catalyst-Coated Membranes for Anion Exchange Membrane Water Electrolyzers

“…In Figure a, the CL exhibits interlaced nanosheet structures grown vertically on the surface of the AEM (Sustainion X37-50). This structure potentially possesses a large effective surface area, facilitating mass transport and thereby enhancing electrochemical reactions. , The morphologies of the CLs on other AEMs were also similar to each other (Figure S4). The cross-sectional FE-SEM image shows that the CL with a thickness of ∼2.5 μm was in uniform and intimate contact with the AEM (Figure b).…”

“…46,47 Furthermore, the uniformly distributed vertically aligned layered nanosheet morphology and amorphous crystallinity of d-Ni 3 Fe 1 provide a large surface area for electrochemical reactions, which enables fast charge-kinetics and mass transport at the MEA−electrolyte interface. 28,38 Electrochemical impedance spectroscopy (EIS) was carried out at an applied voltage of 1.7 V cell to determine the cell resistance (R Ω ) during electrolysis. R Ω represents the sum of the ionic and electronic resistances of each component of the electrolyzer and the contact resistance of each interface.…”

“…These substrates have suitable features of mechanical robustness, chemical stability, and high conductivity, which satisfy various conventional catalyst synthesis methods (hydro-/solvothermal, chemical vapor deposition, electrodeposition, etc. ). − However, such conventional approaches are limited to c -CCSs and cannot be directly applied to c -CCMs due to the low thermal and chemical durability under synthetic conditions and the nonconductive properties of AEMs . It is worth noting that a c -CCM is a potentially preferred MEA fabrication method over a c -CCS because it provides optimal interaction between CLs and the AEM and excludes the performance losses caused by the diffusion of catalyst particles within the GDL. ,, …”

“…The ionomer-free, in-situ deposition technique enables intimate contact between the AEM and CLs, maximizing catalyst utilization for electrochemical reactions . In addition, this direct deposition approach results in significantly higher conductivity at the electrode–electrolyte interface and mass transport properties during electrolysis than typical MEAs obtained from c -CCM and c -CCS. , Furthermore, the uniformly distributed vertically aligned layered nanosheet morphology and amorphous crystallinity of d -Ni 3 Fe 1 provide a large surface area for electrochemical reactions, which enables fast charge-kinetics and mass transport at the MEA–electrolyte interface. , …”

Development of a Multi‐Element Copper‐Phosphorus‐Based Electrode for Efficient Hydrogen Evolution Reaction

“…To assess the electrocatalytic kinetics of HER and the ratedetermining step (RDS), iR-free Tafel plots of the catalytic materials were obtained from the steady-state polarization curves. [41] The theoretical Tafel slopes for Volmer, Tafel, and Heyrovsky processes as the rate-determining step are 120 mV dec À 1 , 30 mV dec À 1 , and 40 mV dec v1 . The Tafel slope of the Ni 2 P/Ni 12 P 5 /Sn 4 P 3 /Cu 3 P@Cu electrode was 45.55 mV dec À 1 after 32 min of anodic dissolution (Figure 5 Electrochemical impedance spectroscopy (EIS) was performed further to elucidate the electrode kinetics under HER operating conditions, EIS and fitting Equivalent circuit were given in Figure 5 (c).…”