Recycled Cathodes in Rechargeable Aqueous Batteries as Ready-Made Electrodes for Oxygen Evolution Catalysis

The development of a low-cost and efficient oxygen evolution reaction (OER) electrode is of critical importance for water electrolysis technologies. The general approach to achieving a high-efficiency OER electrode is to regulate catalytic material structures by synthetic control. Here we reported an orthogonal approach to obtaining the OER electrode without intentional design and synthesis, namely, recycling MnO₂ cathodes from failed rechargeable aqueous batteries and investigating them as ready-made catalytic electrodes. The recycled MnO₂ cathode showed very little Zn²⁺ storage capacity but surprisingly high OER activity with a low overpotential of 307 mV at 10 mA cm^-2 and a small Tafel slope of 77.9 mV dec^-1, comparable to the state-of-the-art RuO₂ catalyst (310 mV, 86.9 mV dec^-1). In situ electrochemical and theoretical studies jointly revealed that the accelerated OER kinetics of the recycled MnO₂ electrode was attributed to the enlarged active surface area of MnO₂ and optimized electronic structure of Mn sites. This work suggests failed battery cathodes as successful catalysis electrodes for sustainable energy development.