Trimetallic Metal Oxides Cr0.5coxru0.5-Xo2-Δ Electrocatalyst with High Performance for Acidic Oxygen Evolution Reaction

The development of acid-sensitive OER (Oxygen Evolution Reaction) electrocatalysts based on ruthenium oxides is a crucial step toward achieving large-scale hydrogen production in low-cost Proton Exchange Membrane (PEM) electrolyzers. However, a major challenge in this field is to overcome the tendency of ruthenium-based metal oxides to dissolve in acidic environments, which affects their long-term stability. In this study, we employed MIL-101(Cr) as a precursor and used a simple room-temperature stirring and annealing process to prepare ternary spinel metal oxides Cr0.5CoxRu0.5-xO2-δ. Detailed physical characterization, combined with electrochemical tests, demonstrated that the introduction of cobalt (Co) reduces the volume of individual catalyst crystallites without disrupting the spinel crystal structure and inherent activity of CrO2-RuO2. Simultaneously, the Co and Cr doping lowers the oxidation state of ruthenium (Ru) within the catalyst system. Lower oxidation states of Ru are more stable during the OER reaction, ensuring the stability of this catalyst to at least 25 hours. Furthermore, Co incorporation raises the energy required for oxygen vacancy formation, reduces the involvement of lattice oxygen, and enhances the catalyst's activity. The best catalyst Cr0.5Co0.17Ru0.33O2-δ exhibits the overpotential of only 224 mV at 10 mA cm−2 in 0.5 M H2SO4. This study offers a viable strategy for developing highly active and stable catalysts in acidic media by controlling the electronic structure of RuO2.