CoMoO4-CoP/NC heterostructure anchored on hollow polyhedral N-doped carbon skeleton for efficient water splitting

Abstract

We report the synthesis and electrocatalytic properties of a CoMoO4-CoP heterostructure anchored on a hollow polyhedral N-doped carbon skeleton (CoMoO4-CoP/NC) for water-splitting applications. The preparation involved the anion exchange of MoO42- to the organic ligand of ZIF-67, the self-hydrolysis of MoO42-, and NaH2PO2 phosphating annealing. CoMoO4 was found to enhance thermal stability and prevent active site agglomeration during annealing, while the hollow structure of CoMoO4-CoP/NC provided a large specific surface area and high porosity that facilitated mass transport and charge transfer. The interfacial electron transfer from Co to Mo and P sites promoted the generation of electron-deficient Co sites and electron-enriched P sites, which accelerated water dissociation. CoMoO4-CoP/NC exhibited excellent electrocatalytic activity for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1.0 M KOH solution, with overpotentials of 122 mV and 280 mV at 10 mA cm−2, respectively. The CoMoO4-CoP/NC‖CoMoO4-CoP/NC two-electrode system only required an overall water splitting (OWS) cell voltage of 1.62 V to achieve 10 mA cm−2 in an alkaline electrolytic cell. In addition, the material showed comparable activity to 20% Pt/C‖RuO2 in a pure water home-made membrane electrode device, demonstrating potential for practical applications in proton exchange membrane (PEM) electrolyzers. Our results suggest that CoMoO4-CoP/NC is a promising electrocatalyst for efficient and cost-effective water splitting.