Dense-Packed RuO 2 Nanorods with In Situ Generated Metal Vacancies Loaded on SnO 2 Nanocubes for Proton Exchange Membrane Water Electrolyzer with Ultra-Low Noble Metal Loading.

Proton exchange membrane water electrolyzer (PEMWE) is a green hydrogen production technology that can be coupled with intermittent power sources such as wind and photoelectric power. To achieve cost-effective operations, low noble metal loading on the anode catalyst layer is desired. In this study, a catalyst with RuO 2 nanorods coated outside SnO 2 nanocubes is designed, which forms continuous networks and provides high conductivity. This allows for the reduction of Ru contents in catalysts. Furthermore, the structure evolutions on the RuO 2 surface are carefully investigated. The etched RuO 2 surfaces are seen as the consequence of Co leaching, and theoretical calculations demonstrate that it is more effective in driving oxygen evolution. For electrochemical tests, the catalysts with 23 wt% Ru exhibit an overpotential of 178 mV at 10 mA cm -2 , which is much higher than most state-of-art oxygen evolution catalysts. In a practical PEMWE, the noble metal Ru loading on the anode side is only 0.3 mg cm -2 . The cell achieves 1.61 V at 1 A cm -2 and proper stability at 500 mA cm -2 , demonstrating the effectiveness of the designed catalyst.