Structural Phase Transition Induced by Ruthenium Doping in Cobalt Diselenide for Enhanced Oxygen Evolution and Reduction Reaction Performance

In this study, a dual-phase bifunctional catalyst containing cubic-phase CoSe2 (c-CoSe2) and monoclinic-phase Co3Se4 (m-Co3Se4) was synthesized via selenization of a zeolitic imidazolate framework (ZIF-67), followed by mechanical ball milling with optimized ruthenium chloride and subsequent pyrolysis. The introduction of Ru doping altered the coordination environment of Co, effectively regulating the ratio between the c-CoSe2 and m-Co3Se4 phases while tailoring the electronic structure of the composite. The synergistic effects of these modifications on catalytic performance were comprehensively investigated through oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) evaluations. The incorporation of Ru triggered a partial phase transformation from c-CoSe2 to m-Co3Se4, which promoted the formation of catalytically active CoOOH species, thereby markedly enhancing both OER and ORR activities. Remarkably, rechargeable zinc-air batteries (ZABs) equipped with the Ru-engineered catalyst demonstrated superior efficiency and long-term stability. This work highlights the pivotal role of phase engineering and heteroatom doping in designing high-performance bifunctional electrocatalysts for next-generation energy storage technologies.