2D Ruthenium–Chromium Oxide with Rich Grain Boundaries Boosts Acidic Oxygen Evolution Reaction Kinetics

Abstract Ruthenium oxide is currently considered as the promising alternative to Ir‐based catalysts employed for proton exchange membrane water electrolyzers but still faces the bottlenecks of limited durability and slow kinetics. Herein, a 2D amorphous/crystalline heterophase ac‐Cr 0.53 Ru 0.47 O 2‐δ substitutional solid solution with pervasive grain boundaries (GBs) is developed to accelerate the kinetics of acidic oxygen evolution reaction (OER) and extend the long‐term stability simultaneously. The ac‐Cr 0.53 Ru 0.47 O 2‐δ shows a super stability with a slow degradation rate and a remarkable mass activity of 455 A g Ru −1 at 1.6 V vs RHE, which is ≈3.6‐ and 5.9‐fold higher than those of synthesized RuO 2 and commercial RuO 2 , respectively. The strong interaction of Cr–O–Ru local units in synergy with the specific 2D structural characteristics of ac‐Cr 0.53 Ru 0.47 O 2‐δ dominates its enhanced stability. Meanwhile, high‐density GBs and the shortened Ru‐O bonds tailored by amorphous/crystalline structure and Cr–O–Ru interaction regulate the adsorption and desorption rates of oxygen intermediates, thus accelerating the overall acidic OER kinetics.