Charge localized atomic Moδ+ site boosting hydrogen evolution in alkaline solution

Abstract

Electrochemical water splitting has drawn tremendous interest for the scalable and sustainable conversion of renewable electricity to clear hydrogen fuel and chemicals. However, the sluggishly kinetics of water dissociation step in alkaline solutions restrict severely the application of hydrogen evolution reaction (HER). Here, we designed and prepared cobalt layers with nitrogen modified atomically dispersed Mo sites (N-Mo/Co SAA) to boost the activity of HER. Density functional theory (DFT) calculations demonstrated that the N can induce the asymmetry charge localization of Moδ+ to facilitate the water dissociation. The energy barriers of water dissociation reduced from 0.48 to 0.35 eV by the charge localized Moδ+ site. High resolution transmission electron microscope (HRTEM) and synchrotron X-ray absorption spectroscopy (XAS) measurements confirmed the structure of N modified atomically dispersed Moδ+. Ambient pressure X-ray photoelectron spectroscopy (AP-XPS) measurements assessed the atomically dispersed Moδ+ site is the active site for water dissociation. Thus, the obtained N-Mo/Co catalyst exhibits record activity with 12 mV overpotential to achieve the current density of 10 mA cm− 2 and Tafel slope of 31 mV dec− 1 in alkaline media, which are superior to 32 mV overpotential for 10 mA cm− 2 and 38 mV dec− 1 Tafel slope on best commercial 20 wt% Pt/C sample in the same condition. This design strategy provided a new pathway to boost the activity of single atom alloy (SAA) by regulating the charge localization of the active site precisely at the atomic-level.