Tungsten‐Mediated Hydroxyl Supply Enhances PtIr Activity Toward Electrochemical Ammonia Oxidation for High‐Performance Direct Ammonia Fuel Cells

ABSTRACT Low‐temperature direct ammonia fuel cells (DAFCs) have gained increasing attention for power generation, but the anodic ammonia oxidation reaction (AOR) still suffers from considerable overpotential. This multistep reaction involves the successive dehydrogenation of adsorbed ammonia triggered by OH – , whereas the consumption kinetics of OH – is too fast to be timely supplemented from bulk electrolyte, which significantly restricts the AOR even for the state‐of‐the‐art PtIr catalyst. Herein, we address this challenge by proposing a tungsten‐mediated hydroxyl supply strategy. Tungsten features high oxophilicity and its incorporation into the PtIr substitutional solid‐solution alloy could effectively trigger O‐down (H 2 O↓) conformation in interfacial water as demonstrated by in situ attenuated total reflection‐Fourier transform infrared (ATR‐FTIR) characterization. This H 2 O↓ conformation promotes OH – transport, which is directly evidenced by an ultralow reaction order with respect to OH – concentration in bulk electrolyte. The hydroxyl dependency of the system is thus greatly alleviated, and the facilitated AOR kinetics is confirmed by a series of in situ characterizations. The optimal PtIrW delivers a superior current density as high as 132.41 A g −1 , representing more than 5‐fold enhancement over commercial PtIr. Once assembled in a DAFC, a remarkable peak power density of 186.03 mW cm −2 is achieved at 60°C.