Active site recovery and N-N bond breakage during hydrazine oxidation boosting the electrochemical hydrogen production

Abstract

Abstract Using hydrazine oxidation reaction (HzOR) substituting for oxygen evolution reaction can realize hydrogen production at largely reduced energy consumption. While the HzOR mechanism and the electrochemical utilization rate of hydrazine are still ambiguous. Herein, a bimetallic phosphide heterostructure nanoarrays (Ni-Co-P/NF) fabricated by an interface engineering strategy was used to catalyze both HzOR and hydrogen evolution reaction (HER), and more intensively, probe the HzOR mechanism. The extra-high HzOR performance is attributed to the instantaneous recovery of metal phosphide active site by hydrazine and the extremely low energy barrier with even a new HzOR pathway of N-N bond breakage, which enables the electrolyzer catalyzed by Ni-Co-P/NF to reach 500 mA cm-2 for H2 production at as low as 0.498 V, and offers a high hydrazine electrochemical utilization rate of 93%. The constructed electrolyzer can be powered by the direct hydrazine fuel cell with Ni-Co-P/NF as anodic catalyst, achieving self-powered hydrogen production at the rate up to 19.6 mol h-1 m-2.