Molybdenum nitride as a metallic photoelectrocatalyst for hydrogen evolution reaction via introduction of electron traps to improve the separation efficiency of photogenerated carriers.

Metallic photoelectrocatalysts possess a wide light absorption range and the fast hydrogen evolution reaction (HER) kinetics, which can be used as the next generation of catalysts towards photoelectrocataytic HER. In this work, molybdenum nitride has been fabricated via an in-suit growth method on metal molybdenum substance (Mo 3 N 2 /Mo foil). The metallic and optical property of Mo 3 N 2 was confirmed by the DFT calculations and experimental results from UV–visible absorption spectrum and valence X-ray photoelectron spectroscopy spectrum. Photocatalytic HER rate of Mo 3 N 2 reached to 158.78 μmol h−1 g−1. Furthermore, Mo 3 N 2 –MoS 2 /Mo foil was prepared to improve photoelectrocatalytic performance. Herein, a suitable energy band alignment for Mo 3 N 2 –MoS 2 /Mo foil was proposed based on experiments and DFT calculations, and the formation of a heterojunction (Mo 3 N 2 –MoS 2) effectively suppressed the recombination of photo-generated carriers. The results of photoelectrocatalytic experiments suggested that the photocurrent density of Mo 3 N 2 –MoS 2 /foil was effectively enhanced about 1.5 times than that of simplex Mo 3 N 2 /Mo foil. The electrochemical experiments (LSV and EIS) indicated that the metallic nature of Mo 3 N 2 was also beneficial to electrocatalytic HER, and the overpotential of Mo 3 N 2 –MoS 2 /Mo foil at 10 mA cm−2 was −173 mV. This work provides a potential candidate for photoelectrocatalytic electrodes. [Display omitted] • Metallic Mo 3 N 2 plays a dominant role in photoelectrocatalytic HER activity. • The metallic and optical nature were verified by experiments and DFT calculation. • Mo 3 N 2 –MoS 2 heterojunction was used to improve the photoelectrocatalytic property. • Schottky barrier effectively suppress the recombination of photoinduced carriers. • Mo 3 N 2 –MoS 2 /Mo foil electrode exhibits superior stability for HER. [ABSTRACT FROM AUTHOR]