Tailoring the Orbital Overlap of RuO2 via Inductive Effect for Durable Proton Exchange Membrane Water Electrolysis

RuO 2 is a promising anode catalyst for PEMWE but suffers rapid degradation at ampere-level current densities. Previous studies have linked the instability of ruthenium-based catalysts to excessive Ru─O covalency, yet the mechanism governing this covalency remains unclear. Here, we introduce isovalent metals (M: Ti 4+ /Hf 4+ ) to modulate the Ru─O bond strength. Density functional theory calculations show that the strong inductive effect of Hf─O enables Hf 4+ to optimize the Ru(4d)–O(2p) orbital overlap, which in turn weakens the Ru─O covalency, thereby suppressing lattice oxygen activity. Experimental results demonstrate that Hf 4+ , which possesses stronger oxophilicity, exhibits superior performance in enhancing both the catalytic activity and durability of Ru 0.7 M 0.3 O 2 (M = Ti or Hf) for the acidic oxygen evolution reaction. In a practical PEMWE device, Ru 0.7 Hf 0.3 O 2 achieves 3 A cm −2 at 1.71 V, corresponding to a specific energy consumption of 44.58 kWh kg −1 H 2 , meeting the U.S. DOE 2026 target (specific energy consumption of 48 kWh kg −1 H 2 ). Moreover, the catalyst operates stably for over 250 h at 1 A cm −2 with a degradation rate more than 48 times lower than that of commercial RuO 2 . This work provides a new strategy for designing high-performance catalysts through the inductive effect.