Effects of d-Block Transition Metal Impurities on a Carbon Cloth/Ni(OH)2 Interface for Electrocatalytic Oxygen Evolution Reaction

Abstract

The layer-structured Ni(OH)2 compound has emerged as a promising electrocatalyst for oxygen evolution reaction (OER). This study unveils how much d-block transition metals, ranging from V, Cr, Mn, Fe, Co, and Cu to Zn, can influence the OER performance and their overpotential. Nanoplate-like Ni(OH)2 synthesized successfully on the as-prepared carbon cloth (CC) was activated by cyclic voltammetry (CV) in a purified 1 M KOH electrolyte. The electrochemical measurements indicate that Fe as an impurity profoundly decreases the overpotential up to 138 mV at 10 mA cm–2 while significantly increasing current density. Meanwhile, its Tafel slope drops by as much as 46 mV dec–1. Interestingly, α-Ni(OH)2 contained nanoplate-like particles that would be preserved in the presence of iron as an impurity, with outstanding long-term stability, as evidenced by chronopotentiometry analysis. Comparatively, the presence of other transition metal impurities, like V, Cr, Mn, Cu, and Zn, negligibly improves the required overpotential, which is much less than the effect of a tiny amount of Fe. All characterizations, including XRD, HR-TEM, XPS, CV, LSV, and EIS, prove that iron increases the OER performance while prohibiting nickel from oxidation. The suppression of nickel oxidation is a characteristic that among the transition metals only iron shows. This work provides information on which electronic interaction between nickel and transition metal atoms on the surface can influence activity enhancement. Furthermore, the suggested method can be used for the activation of Ni(OH)2, providing a rapid screening method to evaluate the effects of heteroatom impurities on the OER performance of nickel-based compounds.