Novel catalyst coatings on gas diffusion layers for improved proton exchange membrane water electrolysis: A microscopic analysis of D-Orbital electron interactions in Co_0.75Ru_0.21Ir_0.04O_0.9

Proton exchange membrane water electrolysis (PEMWE) has emerged as a reliable water splitting technology in recent years. The oxygen evolution reaction (OER) at the anode, is the rate-determining step in water electrolysis, and therefore, the kinetic and mass transfer performance of the oxygen evolution reaction should be further studied. Efficient electron and water transfer between the catalyst layer (CL) and gas diffusion layer (GDL) is crucial for optimizing PEMWE performance. In this work, Ru-core modified materials were successfully synthesized via a hydrothermal method and then spray-coated onto the surface of the gas diffusion layer. Physical and electrochemical characterization showed that 0.10 mg cm⁻² was the optimal dosage of the coating. The single cell with this optimal coating exhibited a well-promoted and outstanding performance that a cell voltage of 1.71 V@1 A cm⁻² and an overpotential of 222 mV@10 mA cm⁻². This enhancement was primarily attributed to the improved ohmic and mass transfer properties. Specifically, the promotion of kinetic and mass transfer performance was due to the attraction of the empty d-orbitals of Ru, Co, and Ir, which enhanced electron transmission between the catalyst layer (CL) and gas diffusion layer. Physical analysis revealed that the reductive gaseous products caused Co (Ⅲ) to transform to Co (Ⅱ) and the formation of Co₃O₄ and RuO₂ was well-protected by the Co (II)-rich Co₃O₄ phase due to its reductivity nature. Additionally, the effusion of gaseous products from the solid phase accelerated pore formation, thereby increasing the specific surface area of the material.