An amorphous/nanocrystalline NixP/Ni heterojunction for electrooxidation of hydrazine

Abstract

Transition metal phosphides have emerged as leading candidates for the anode applications of direct hydrazine fuel cells (DHzFCs). But most recent studies have focused on single-phase crystalline phosphides, leaving multi-phase and amorphous materials largely unexplored. Herein, we report the fabrication of a Ni foam-supported heterojunction catalyst composed of amorphous Ni_xP and crystalline Ni nanoparticles by a one-step electrodeposition method. The a-Ni_xP/Ni/NF catalyst has a favorable combination of high electrochemically active surface area, good electrical conductivity and, in particular, improved intrinsic activity towards the hydrazine oxidation reaction (HzOR) compared to the amorphous and nanocrystalline components. Benefiting from these attributes, a-Ni_xP/Ni/NF exhibits exceptionally high activity towards alkaline HzOR, excellent stability and a nearly 100% selectivity for four-electron hydrazine electrooxidation, surpassing most existing HzOR electrocatalysts. Encouraged by its outstanding catalytic performance, we further assembled a DHzFC using a-Ni_xP/Ni as the anode catalyst and tested its performance at room temperature.