Multigrain Ruthenium Nanocrystals with Enriched (101¯${{\bar{1}}}$1) Facets for Enhanced Hydrogen Oxidation in Anion Exchange Membrane Fuel Cells

Ruthenium-based materials are promising alternatives to expensive platinum for the anodic hydrogen oxidation reaction (HOR) in anion exchange membrane fuel cells (AEMFCs), but face stability issues due to the strong oxophilicity. Here, an oxidation-resistant ruthenium multigrain catalyst is reported that exposes rich (10 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:mover><mml:mn>1</mml:mn> <mml:mo>¯</mml:mo></mml:mover> <mml:annotation>${{\bar{1}}}$</mml:annotation></mml:semantics> </mml:math> 1) facets for high-performing HOR catalysis in alkaline electrolytes. The catalyst exhibits a high kinetic current density of 61 mA cm^-2 at an overpotential of 50 mV, which is 25.6- and 7.8-times higher than that of commercial ruthenium-carbon and platinum-carbon catalysts, respectively. Moreover, it also demonstrates a wide stability window up to 0.3 V versus the reverse hydrogen electrode and enhanced tolerance to carbon monoxide. An AEMFC containing this catalyst at the anode achieves peak power densities of 1.31 and 1.06 W cm^-2 under hydrogen-oxygen and hydrogen-air conditions at 90 °C, respectively, and operates steadily. Experimental and theoretical studies reveal that the (10 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:mover><mml:mn>1</mml:mn> <mml:mo>¯</mml:mo></mml:mover> <mml:annotation>${{\bar{1}}}$</mml:annotation></mml:semantics> </mml:math> 1) facet possesses a higher oxidation barrier and lower hydrogen oxidation barrier than the common (0002) facets, enabling the exceptional HOR performances in alkali.