Dynamic activity at the interface and surface in porous NiFeSe/NiCoSe/NF to enhance overall water splitting

Designing a bifunctional electrocatalyst with noble-free metal is still a challenge. In this work, we synthesized NiFeSe/NiCoSe/NF as a bifunctional electrocatalyst via two-step hydrothermal methods. With a strategy of interface engineering, the synthesized NiCoSe nanosheets precursor can produce a large contact area and promote the diffusion of Co ions. Furthermore, a porous structure was fabricated via a surface engineering technique, where zero-valent Selenium (Se ⁰ ) formed on the surface of catalysts during the second hydrothermal process and then subsequently dissolved in the electrochemical activation process with leaving many pits on the surface of catalysts. Because of the enhanced electron transfer capability, large specific surface area and multimetallic synergistic effects, the synthesized NiFeSe/NiCoSe/NF presented low overpotential of 171 and 91 mV at the current density of 10 mA cm ⁻² for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in 1.0 M KOH. The overall water splitting system using NiFeSe/NiCoSe/NF as both the cathode and anode required a small cell voltage of 1.50 V to deliver a current density of 10 mA cm ⁻² with the stability about 300 hours. This work is beneficial to design highly stable and effective catalysts for splitting water.