An interface-engineered Co₂P/CoMoP₂ heterojunction with greatly improved electrocatalytic activity in water/seawater splitting

It is essential to design and synthesize non-noble metal-based electrocatalysts for the highly efficient hydrogen evolution reaction (HER). In this study, we have successfully prepared a self-supporting phosphide heterostructured electrocatalyst, where CoMoP2 nanosheets are well distributed on the surface of Co2P hollow nanobricks on Ni foam. The testing results demonstrated that the as-prepared Co2P/CoMoP2 exhibited excellent HER performance with an overpotential of 36 mV and 43 mV (at 10 mA cm(-2)) in alkaline water and seawater electrolyte, respectively. Meanwhile, it also showed good oxygen evolution reaction (OER) activity at 10 mA cm(-2)with an overpotential of 254 mV in alkaline water and 268 mV in alkaline seawater electrolyte, respectively. Theoretical research studies have verified that the activation energy barrier of H2O on the surface of CoMoP2 was 0.63 eV, while that on the surface of Co2P was 0.73 eV, indicating that CoMoP2 can promote the Volmer step. Also, the electronic redistribution at the interface enabled the Co2P/CoMoP2 heterojunction to achieve the ideal Gibbs free energy of hydrogen adsorption (0.16 eV). Interface engineering provides a simple and efficient approach for designing highly efficient Co2P-based electrocatalysts.