The Intrinsic Effect of Spontaneous Chemical Reduction on Phosphorus-Doped Cobalt Toward Hydrazine Oxidation Reaction

Transition metals (TMs) have caught great attention as the promising electrocatalysts for hydrazine oxidation reaction (HzOR). However, the critical factor that determines the superior HzOR activity on TMs has not been understood in-depth, which hampers the precise design for admirable electrocatalysts. Herein, phosphorus-doped cobalt (P_x/Co) have been designed and fabricated by a cyclic voltammetry (CV) approach to catalyze hydrazine oxidation. A spontaneous chemical reduction, which in situ recovers Co-PO_x to Co-P_x by hydrazine molecules has been confirmed in HzOR. A lower d band center and more charged Co sites in P_x/Co was positively associated with a faster kinetics of spontaneous chemical reduction. We also found that the HzOR mechanism followed both the N─N bond breakage path and the traditional dehydrogenation path simultaneously on P_x/Co in an alkaline environment. A rapid spontaneous chemical reduction was more inclined to drive the HzOR to proceed along N─N bond breakage path, which accelerated the HzOR kinetics and endowed the phosphorus-doped cobalt with a higher electro-catalytic performance. Our work provides a new perspective to understand the intrinsic correlation among the electronic state of active sites, the kinetics of spontaneous chemical reduction and the electro-catalytic mechanism of HzOR on TMs.