Bimetallic NiCo-MOF engineering on foam nickel for efficient oxygen evolution reaction in wide-pH-value water and seawater

Abstract

Oxygen evolution reaction (OER) is a half-reaction that transpires at the anode during water electrolysis. It is a controlling step in the process because of slow kinetics. Therefore, developing OER catalysts with low cost, enduring stability, and wide-pH-value adaptability is a significant challenge. In this article, NiXCo2.4-X-MOF (x = 0.4, 0.6, 0.8, 1) catalysts were synthesized via hydrothermal on nickel foam (NF). The proportion and hydrothermal temperature can affect the performances, and the optimal catalyst is obtained with x = 0.6 and hydrothermal temperature is 150℃ (Ni0.6Co1.8-MOF). This catalyst exhibits outstanding electrocatalytic performances. The overpotentials are 1.77, 1.61, and 1.68 V in 1 M PBS (pH = 7), 1 M KOH, and alkaline seawater at 20, 200, and 200 mA cm−2 with excellent stability towards OER, respectively. In-situ SERS results suggest that during the OER process, hydroxyoxides are formed on the catalyst surface, which serves as the actual active substance. Furthermore, XPS analysis of the OER reaction reveals the formation of M−O and high-valence state oxides. DFT calculations confirm that Ni0.6Co1.8-MOF/NiCoOOH acts as the genuine active site for the OER, formed through the reconstruction of Ni0.6Co1.8-MOF, lowering the energy barrier for OOH* formation further accelerates the reaction kinetics of the OER. This study indicates the broad application prospects of MOFs in wide-pH-value and seawater.