Heterogeneous cobalt-iron phosphide nanosheets formed by in situ phosphating of hydroxide for efficient overall water splitting

Transition metal phosphides (TMPs) have emerged as one of the most promising electrocatalysts toward water decomposition because of exceptional catalytic properties and abundant reserves. Herein, we successfully construct an unique CoP 3 /Fe 2 P nanosheet catalyst grown on Ni foam (CoP 3 /Fe 2 P@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 CoP 3 -Fe 2 P heterointerfaces can further optimize hydrogen adsorption energy (ΔG H* ) to effectively reduce free energy barrier. Thus, the CoP 3 /Fe 2 P@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, comparable to most reported catalysts. This work affords a promising approach for synthesis of binary and above transition metal phosphides. • A unique CoP 3 /Fe 2 P heterostructure electrocatalyst is synthesized via a successive solvothermal-phosphating strategy. • Abundant heterointerfaces and lots of nanopores are formed by in-situ phosphating CoFe-LDHs precursor. • The CoP 3 /Fe 2 P@NF-2 sample acts as effective bifunctional electrocatalysts towards OER and HER. • The CoP 3 /Fe 2 P@NF-2 NSs || CoP 3 /Fe 2 P@NF-2 NSs electrolyzer provides a low cell voltage of 1.53 V at 20 mA cm -2 . • The DFT results confirm that the CoP 3 -Fe 2 P heterointerfaces can further optimize hydrogen adsorption energy.