Surface phosphorization of hierarchically nanostructured nickel molybdenum oxide derived electrocatalyst for direct hydrazine fuel cell

Abstract

Non-faradaic catalytic decomposition of hydrazine (N2H4) is a vital but underappreciated problem for direct hydrazine fuel cell (DHFC). Herein, a careful study of a nickel molybdenum oxide derived catalyst for N2H4 electrooxidation is reported, with special focus on the method for effectively suppressing non-faradaic decomposition of hydrazine as well as the underlying mechanism. A hierarchically nanostructured catalyst consisting of tiny Ni10Mo alloy nanoparticles dispersed on porous NiMoO nanosheets is synthesized using a simple hydrothermal method followed by reductive annealing treatment. Thus-prepared catalyst shows high activity towards N2H4 electrooxidation, but is entangled with the problematic selectivity towards non-faradaic decomposition of N2H4. Our study find that this problem can be circumvented by a controlled phosphorization method. The resultant catalyst (Ni2P@Ni10Mo/Ni-Mo-O/NF) exhibits exceptionally high activity, excellent durability and nearly 100 % selectivity towards N2H4 electrooxidation. A detailed structural characterization and density functional theory calculations are conducted to understand the phosphorization-induced modification of catalytic property.