Single atom tungsten doped ultrathin \u03b1-Ni(OH)2 for enhanced electrocatalytic water oxidation

Junqing Yan,Jai White,Youyong Li,Tianyi Ma,Lingqiao Kong,Yujin Ji,Shengzhong Liu,Jing Zhang,Pengfei An,Shuit-Tong Lee

doi:10.1038/s41467-019-09845-z

Abstract

Electrocatalytic water oxidation is a rate-determining step in the water splitting reaction. Here, we report one single atom W6+ doped Ni(OH)2 nanosheet sample (w-Ni(OH)2) with an outstanding oxygen evolution reaction (OER) performance that is, in a 1 M KOH medium, an overpotential of 237 mV is obtained reaching a current density of 10 mA/cm2. Moreover, at high current density of 80 mA/cm2, the overpotential value is 267 mV. The corresponding Tafel slope is measured to be 33 mV/dec. The d0 W6+ atom with a low spin-state has more outermost vacant orbitals, resulting in more water and OH− groups being adsorbed on the exposed W sites of the Ni(OH)2 nanosheet. Density functional theory (DFT) calculations confirm that the O radical and O-O coupling are both generated at the same site of W6+. This work demonstrates that W6+ doping can promote the electrocatalytic water oxidation activity of Ni(OH)2 with the highest performance.

Highlights

Electrocatalytic water oxidation is a rate-determining step in the water splitting reaction
The d0 W6+ atom with a low spin-state has more outermost vacant orbitals, resulting in more water and OH− groups being adsorbed on the exposed W sites of the Ni(OH)[2] nanosheet
Stahl et al first detected the formation of Fe4+ during the oxygen evolution reaction (OER) process by Mössbauer Spectroscopy and reported that the species was not kinetically competent to serve as the active site in water oxidation[32]

Summary

Introduction

Electrocatalytic water oxidation is a rate-determining step in the water splitting reaction. We report one single atom W6+ doped Ni(OH)[2] nanosheet sample (w-Ni(OH)2) with an outstanding oxygen evolution reaction (OER) performance that is, in a 1 M KOH medium, an overpotential of 237 mV is obtained reaching a current density of 10 mA/cm[2]. By using operando X-ray absorption spectroscopy and computational methods, Bell et al proposed that the Fe doping in NiOOH produced short Fe–O bonds These active bond sites were said to have resulted in the high OER performance with low overpotentials and optimal adsorption energies of OER intermediates being observed[31]. The OER performance of Ni(OH)2-based electrocatalysts still needs improvement by doping, and the finding of a suitable element remains to be developed. It is still necessary to find one suitable reaction site for achieving both the formation and migration of intermediates

Methods

Results

Conclusion