Lattice Expansion Induced Charge Redistribution Enhances Activity and Durability in Ruthenium Oxide for Proton Exchange Membrane Water Electrolysis

Proton exchange membrane water electrolysis (PEMWE) requires highly active and durable acidic oxygen evolution reaction (OER) anodes, yet the benchmark IrO2 is limited by its scarcity and high cost. RuO2 is a more cost-effective and active alternative, but suffers from poor acidic stability due to lattice oxygen instability and Ru over-oxidation under anodic conditions. Here we incorporate larger Zr4+ (4 d0) into rutile RuO2 to form Ru1-xZrxO2 solid-solution nanosheets. Diffraction and spectroscopic analyses reveal that Zr4+ incorporation into the RuO2 lattice induces long-range lattice expansion, elongates Ru-O bonds, and thereby drives local charge redistribution within the Ru-O framework. Consequently, at an optimal Zr content of ∼0.3, this modulation optimizes OER intermediate adsorption, stabilizes the oxygen framework, and suppresses RuO4-like species. The optimized Ru0.7Zr0.3O2 anode exhibits superior PEMWE performance, with cell voltages of 1.57 and 1.77 V at 1.0 and 3.0 A cm−2, and a specific energy consumption of 44.28 kWh kg−1 H2, surpassing the U.S. DOE 2026 target of 48 kWh kg−1 H2. Additionally, the catalyst demonstrates stable operation for over 200 h at 1.0 A cm−2. This work establishes lattice expansion induced charge redistribution as an effective strategy to simultaneously enhance the activity and durability of ruthenium oxide for PEMWE.