This study explores a novel cobalt-based selenide pre-catalyst, o-c-CoSe₂-Ni, and its application in water electrolysis and zinc–ethanol–air batteries. The researchers modulate the spin state of cobalt by adjusting its coordinating environment through atomic substitution and crystalline symmetry change. In situ EIS and Raman spectroscopy reveal that o-c-CoSe₂-Ni undergoes a phase transition to CoOOH/Co₂O₃, forming active sites for ethanol oxidation reaction (EOR). The moderate d²z² + dx²-y² orbital occupancy is found to optimize EOR activity, with the intermediate-spin state of Co₃⁺ enhancing both reactant capture and product generation. The as-prepared catalyst shows lower potential and enhanced stability in EOR, with a voltage shift of 190 mV at 50 mA cm⁻² in hybrid water electrolysis and reduced charging voltage and improved cycling stability in zinc–ethanol–air batteries. The work demonstrates a promising strategy for efficient electrocatalysts in water electrolysis and innovative zinc–ethanol–air batteries.This study explores a novel cobalt-based selenide pre-catalyst, o-c-CoSe₂-Ni, and its application in water electrolysis and zinc–ethanol–air batteries. The researchers modulate the spin state of cobalt by adjusting its coordinating environment through atomic substitution and crystalline symmetry change. In situ EIS and Raman spectroscopy reveal that o-c-CoSe₂-Ni undergoes a phase transition to CoOOH/Co₂O₃, forming active sites for ethanol oxidation reaction (EOR). The moderate d²z² + dx²-y² orbital occupancy is found to optimize EOR activity, with the intermediate-spin state of Co₃⁺ enhancing both reactant capture and product generation. The as-prepared catalyst shows lower potential and enhanced stability in EOR, with a voltage shift of 190 mV at 50 mA cm⁻² in hybrid water electrolysis and reduced charging voltage and improved cycling stability in zinc–ethanol–air batteries. The work demonstrates a promising strategy for efficient electrocatalysts in water electrolysis and innovative zinc–ethanol–air batteries.