Heterogeneous Cobalt-Iron Phosphide Nanosheets Formed by in Situ Phosphating of Hydroxide for Efficient Overall Water Splitting

Abstract

Transition metal phosphides (TMPs) have emerged as one of the most promising electrocatalysts toward water decomposition. Herein, we successfully construct a unique CoP3/Fe2P nanosheet catalyst grown on Ni foam (CoP3/Fe2P@NF NSs) via a successive solvothermal-phosphating strategy for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). It should be emphasized that abundant heterointerfaces and lots of nanopores are formed by in-situ phosphating CoFe layered double hydroxides (CoFe-LDHs) precursor. Specifically, the redistribution of electrons at heterogeneous interfaces provides more active sites for reactant molecules or intermediates, and abundant nanopores on the nanosheets facilitate escape of resulting gas, thus releasing active sites in time. Density functional theory (DFT) calculation also proves that CoP3-Fe2P heterointerfaces can further optimize hydrogen adsorption energy (ΔGH*) to effectively reduce free energy barrier. Thus, the CoP3/Fe2P@NF-2 catalyst presents extraordinary electrocatalytic performance towards HER and OER with overpotentials of 81 mV and 236 mV at 10 mA cm-2. As an encouraging result, it provides a low voltage of 1.53 V at 20 mA cm-2 and satisfactory cycling stabilization of over 28 h.

Keywords: Transition metal phosphides, Heterostructures, Hydrogen evolution reaction (HER), Oxygen Evolution Reaction (OER), Nanosheet arrays.