The S-Fe(Ni) sub-surface active sites for efficient and stable overall water splitting

Abstract

Balancing catalytic efficiency and stability is always a critical and challenge issue for energy related research. Here we propose a reaction reconstruction strategy to create active sites in the sub-layer of sulfur-modified transition metal-based catalysts, which can both achieve a high efficiency and exhibit an excellent stability for overall water splitting. The sub-layer active sites of S-Fe and S-Ni are evidenced by the bulk-sensitive X-ray absorption spectroscopy (XAS), while they cannot be observed by the surface-sensitive X-ray photoelectron spectroscopy. Theoretical calculations reveal that the sub-layer active sites can promote the water dissociation and accelerate the formation of high-energy peroxyl groups in anodes to achieve a high efficiency, while the surface layer can protect the sub-layer sites for excellent stability. The high stability is also confirmed by in-situ XAS. As a result, the obtained bi-functional catalyst as both cathode and anode can achieve a current density of 10 mA cm−2 for overall water splitting at a low cell voltage of 1.53 V (1.81 V for 100 mA cm−2), with an excellent stability over 200 h, which outperforms the benchmark Pt/C-RuO2/NF electrodes.