Electrooxidation of Hydrazine Utilizing High-Entropy Alloys: Assisting the Oxygen Evolution Reaction at the Thermodynamic Voltage

Hydrazine electrooxidation is an important reaction as it assists in decreasing the OER overvoltage. Herein, we report the utilization of high entropy nano-catalyst alloy for the electrooxidation of hydrazine. High entropy nano-catalyst comprising five elements (Ag, Au, Pt, Pd, Cu) shows profound activity towards this molecule at low overvoltage. An intriguingly high entropy nano-catalyst prepared by the casting-cum-cryomilling method is endowed with unique catalytic activity for HzOR. Detailed analysis of gaseous product points to the formation of nitrogen as well as oxygen as the oxidation product, a sign of accompanying oxygen evolution reaction (OER). Interestingly, significant oxygen is detected at 1.13 V (RHE) in a neutral buffered medium, confirming that OER is functional at a voltage near to the thermodynamic voltage of 1.23V (RHE). The quantitative contribution of each hydrazine and OER reaction is ascertained which explains a vital insight into this reaction. Density functional theory calculations showed that both HzOR and OER assist each other where the electron-donating effect of H2O to the surface can reduce the endothermicity of the HzOR. Whereas, the electron acceptance of *NHNH2 helps in the favorable overlap of the HEA Fermi level and vacant states with the HOMO of H2O.