A high-efficiency NiFeSe4/NiSe2 bifunctional electrocatalyst with outstanding oxygen evolution reaction and overall water splitting performance

Abstract

Developing cost-effective electrocatalysts for overall water splitting is an effective approach to produce green hydrogen and oxygen. A NiFeSe₄/NiSe₂ heterostructure catalyst for high-efficiency HER and OER was effectively created using an in situ growth preparation approach in this study. The basic crystal structure of the material was altered by selenization, which facilitates electron redistribution within the material. Furthermore, the heterostructure formed following selenization can not only improve the material's conductivity but also give additional active area for catalysis. Meanwhile, the built-in electric field aided in electron redistribution. The NiFeSe₄/NiSe₂-8 h catalyst demonstrated excellent performance, requiring an overpotential of only 218 mV (OER) and 121 mV (HER) to achieve a current density of 10 mA cm⁻². The overall water splitting reaction was carried out at 1.572 V using the NiFeSe₄/NiSe₂-8 h bifunctional catalyst as the cathode and anode of the reaction. Stability is also an important component in determining the quality of materials. The NiFeSe₄/NiSe₂-8 h material reacted continuously at diverse current densities (including low and high current densities) for 36 h with no noticeable performance loss. This work provides a feasible method for preparing an economical and efficient electrocatalyst by adjusting the electrocatalytic performance through heterojunction engineering.