Cobalt-Doped Ru@RuO2 Core–Shell Heterostructure for Efficient Acidic Water Oxidation in Low-Ru-Loading Proton Exchange Membrane Water Electrolyzers

Proton exchange membrane water electrolysis (PEMWE) is a highly promising hydrogen production technology for enabling a sustainable energy supply. Herein, we synthesize a single-atom Co-doped core-shell heterostructured Ru@RuO₂ (Co-Ru@RuO₂) catalyst via a combination of ultrafast pulse-heating and calcination methods as an iridium (Ir)-free and durable oxygen evolution reaction (OER) catalyst in acidic conditions. Co-Ru@RuO₂ exhibits a low overpotential of 203 mV and excellent stability over a 400 h durability test at 10 mA cm^-2. When implemented in industrial PEMWE devices, a current density of 1 A cm^-2 is achieved with only 1.58 V under an extremely low catalyst loading of 0.34 mg_Ru cm^-2, which is decreased by 4 to 6 times as compared to other reported Ru-based catalysts. Even at 500 mA cm^-2, the PEMWE device could work stably for more than 200 h. Structural characterizations and density functional theory (DFT) calculations reveal that the single-atom Co doping and the core-shell heterostructure of Ru@RuO₂ modulate the electronic structure of pristine RuO₂, which reduce the energy barriers of OER and improve the stability of surface Ru. This work provides a unique avenue to guide future developments on low-cost PEMWE devices for hydrogen production.