Ligand-regulated Ni-based coordination compounds to promote self-reconstruction for improved oxygen evolution reaction

Abstract

The Ni-based coordination compounds, during oxygen evolution reaction (OER), self-reconstruct to produce NiOOH, which are the real active sites. Thus, encouraging the self-reconstruction of pre-catalysts to generate more NiOOH species emerges as an effective strategy for enhancing the activity. In this research, we utilized three coordination compounds, Ni(N(CN)2)2, Ni(NCN), and Ni(HNCN)2, to examine the effect of three distinct ligands (-N(CN)2-, -HNCN-, and -NCN-) on the local electronic structure of coordinated Ni, aiming to promote the degree of self-reconstruction during the OER. XPS studies and in-situ Raman spectroscopy revealed a significant relationship between the electron-donating properties of coordinated Ni and the self-reconstruction abilities of the pre-catalysts. Notably, Ni coordinated with -N(CN)2- exhibits a high tendency to donate electrons, leading to facile reconstruction of Ni(N(CN)2)2 into Ni(OOH)-(N(CN)2). As a result, Ni(OOH)-(N(CN)2)2 displays high OER activity (264 mV@10 mA·cm-2 and Tafel 40 mV·dec-1) in comparison to Ni(OOH)-(NCN) (290 mV@10 mA·cm-2 and Tafel 55.63 mV·dec-1) and Ni(OOH)-(HNCN) (307 mV@10 mA·cm-2 and Tafel 77.7 mV·dec-1). These finding offers new perspectives on designing and developing innovative catalysts to enhance OER efficiency.