Lead-doped ruthenium-iridium oxide catalysts for durable acidic oxygen evolution in proton exchange membrane electrolyzers at 3 A cm⁻²

Widespread deployment of proton exchange membrane water electrolyzers (PEMWE) relies on acid-stable oxygen evolution reaction (OER) catalysts capable of operating at high current densities. Inspired by the robust chemistry of lead-acid batteries, we introduce lead (Pb) into ruthenium-iridium mixed oxide (RuIrO_x) through a facile sol–gel method. The as-prepared RuIrPbO_x nanoparticulate catalysts with the optimal composition (Ru_0.5Ir_0.4Pb_0.1O_x) achieve an overpotential of 241 mV at 10 mA cm⁻² and exceptional stability of 1000 h at a high current density of 100 mA cm⁻² without degradation. In situ differential electrochemical mass spectrometry indicates that doping RuIrO_x with an appropriate amount of Pb helps to suppress the participation of lattice oxygen during OER, contributing to structural preservation and long-term stability. Density functional theory calculations reveal that Pb doping effectively regulates the electronic structure of the Ru sites, reducing Ru–O covalency, which in turn increases the Ru dissolution energy and therefore prevents Ru leaching—a key degradation pathway for Ru-containing OER catalysts. When integrated into a membrane electrode assembly, the PEMWE cell can operate at a large current density of 3.0 A cm⁻² under 1.96 V (at 60 °C) for 400 h with minimal performance degradation, demonstrating the significant potential of the Ru_0.5Ir_0.4Pb_0.1O_x as an efficient and durable OER catalyst for practical applications under demanding conditions.