Dealloy-driven hollow porous self-supported electrodes enabling ultra-low precious metal usage in high-performance PEMWE

The principal challenge in proton exchange membrane water electrolysis (PEMWE) lies in improving electrocatalytic performance while minimizing precious metal usage. Herein, we present an innovative approach for the direct fabrication of nanostructured hollow porous RuIrO_x (NHP-RuIrO_x) on a porous transport layer with ultra-low Ru and Ir loadings (54 μg_Ru+Ircm⁻²) via electrochemical deposition followed by dealloying of the sacrificial layer. This unique structure significantly increases the electrochemical surface area while simultaneously improving intrinsic kinetics through surface reconstruction and electronic modulation, thereby resulting in superior electrocatalytic performance. The developed NHP-RuIrO_x requires overpotentials of only 192 and 22 mV at 10 mA cm⁻² for oxygen and hydrogen evolution reaction (OER and HER), respectively, with exceptional mass activities of 2483 and 1188 Ag_Ru+Ir⁻¹. Moreover, as a bifunctional electrocatalyst in a PEMWE single cell, the NHP-RuIrO_x demonstrates outstanding performance, achieving 1.0 A cm⁻² at 1.76 V with superior stability for 150 h at 1 A cm⁻². Remarkably, such performance is achieved with an ultra-low total precious metal loading of only 0.108 mg_Ru+Ircm⁻² across both electrodes. This innovative strategy addresses the primary challenge in PEMWE and provides new insights for electrocatalyst development in acidic electrolytes.