Chen Song

Substituting the anodic oxygen evolution reaction (OER) with ethanol oxidation offers a promising route to lower the energy consumption of anion-exchange-membrane (AEM) electrolysis, but selective oxidation at industrially relevant current densities is often undermined by the emergence of OER-active states. Here, we identify stabilized Ni³⁺ oxyhydroxide as the key state that redirects anodic Ni chemistry away from oxygen evolution and toward selective ethanol oxidation under high-current operation. On a metallic Ni/defect-rich NiO heterointerface, anodic polarization triggers surface hydroxylation while retaining strong electronic coupling across the interface. Mechanistic studies combining operando Raman spectroscopy, post-reaction TEM/XPS, and density functional theory reveal that interfacial charge transfer facilitates early Ni²⁺/Ni³⁺ conversion, stabilizes Ni³⁺ oxyhydroxide species, decreases the OH* deprotonation barrier, and inhibits overoxidation toward OER. This mechanism delivers 100 mA cm⁻² at only 120 mV and preserves selective, bubble-free ethanol oxidation up to 900 mA cm⁻². In an ethanol-hybrid AEM electrolyzer, the corresponding anode lowers the cell voltage by 370 mV at 1.0 A cm⁻² compared with conventional water electrolysis and sustains stable electrolysis for 200 h at 0.5 A cm⁻². Our results establish Ni³⁺ oxyhydroxide stabilization as a general design principle for high-rate selective anodic oxidation and energy-efficient hydrogen production.

Protonic ceramic fuel cells (PCFCs) have been recognized as promising power generation devices for future clean energy systems, owing to their relatively low activation energy for proton migration and high energy conversion efficiency. In certain application scenarios, the use of N₂O (a potent greenhouse gas), as an alternative oxidant to air, presents a feasible strategy. Herein, we report for the first time the operation of PCFCs employing N₂O as the oxidant. A hybrid Pr₂Ni_0.6Co_0.4O_4-δ (PNCO-214) catalyst is developed, comprising Ruddlesden-Popper (R-P) structured Pr₄Ni_1.8Co_1.2O_10-δ (PNCO-4310) and Fluorite structured Pr₆O₁₁ (PO-611), which synergistically exhibits exceptional catalytic activity toward both N₂O decomposition and the oxygen reduction reaction, achieving over 92% conversion and area specific resistance of 1.301 Ω·cm² at 600 °C. Quasi-in-situ temperature-dependent FTIR and electrochemical impedance spectroscopy analyses reveal that abundant oxygen vacancies in PNCO-214 facilitate rapid adsorption and dissociation of N₂O into N₂ and O₂, while also promoting the surface exchange kinetics of proton/oxygen during ORR. When applied in an anode-supported single cell with PNCO-214 cathode operating under N₂O, outstanding power density and low resistance are achieved, delivering 0.801 W·cm^-2 and 0.245 Ω·cm² at 600 °C. Satisfactory performance is also maintained even when the temperature is reduced to 500 °C. Furthermore, the single cell demonstrates relatively good stability with negligible degradation over 130 hours at 600 °C and 0.7 V. These findings underscore the potential of PNCO-214 as a highly effective cathode catalyst for enabling the use of N₂O as a viable oxidant in PCFCs for specific industrial applications.