CeO₂/(NiFe)₃Se₄ Heterostructures for Overall Water Splitting

Developing nonprecious metal-based bifunctional electrocatalysts toward both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) with low cost, high efficiency, and long-term stability is of great significance for alkaline electrolytic water splitting. In this work, a CeO2/(NiFe)3Se4 heterostructure is prepared by chemical deposition on the surface of (NiFe)3Se4 nanoarrays grown on nickel–iron foam (CeO2/(NiFe)3Se4/NIFs). The CeO2/(NiFe)3Se4/NIFs electrocatalysts exhibit a low OER overpotential of only 140 mV at 10 mA cm–2 and a high stability of 300 h at 230 mA cm–2, while an HER overpotential of 74 mV at 10 mA cm–2 is obtained. In addition, the CeO2/(NiFe)3Se4/NIF||CeO2/(NiFe)3Se4/NIF bipolar electrolytic cell needs only a voltage of 1.493 V at 10 mA cm–2, which is comparable to that of commercial Pt/C/NIF||IrO2/NIF bipolar electrolytic cells and superior to that of (NiFe)3Se4/NIF||(NiFe)3Se4/NIF bipolar electrolytic cells (1.55 V). The excellent electrocatalytic activity stems from the special electron transfer mechanism formed by Ce4+/Ce3+ that facilitates the charge transfer process. This work provides an effective surface engineering strategy to design high-efficiency bifunctional electrocatalysts for producing clean hydrogen.