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 (Mo3N2/Mo foil). The metallic and optical property of Mo3N2 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 Mo3N2 reached to 158.78 mu mol h(-1) g(-1). Furthermore, Mo3N2-MoS2/Mo foil was prepared to improve photoelectrocatalytic performance. Herein, a suitable energy band alignment for Mo3N2-MoS2/Mo foil was proposed based on experiments and DFT calculations, and the formation of a heterojunction (Mo3N2-MoS2) effectively suppressed the recombination of photogenerated carriers. The results of photoelectrocatalytic experiments suggested that the photocurrent density of Mo3N2-MoS2/foil was effectively enhanced about 1.5 times than that of simplex Mo3N2/Mo foil. The electrochemical experiments (LSV and EIS) indicated that the metallic nature of Mo3N2 was also beneficial to electrocatalytic HER, and the overpotential of Mo3N2-MoS2/Mo foil at 10 mA cm(-2) was -173 mV. This work provides a potential candidate for photoelectrocatalytic electrodes. (c) 2021 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.

Automated summary

Metallic photoelectrocatalysts with wide light absorption range and fast hydrogen evolution reaction kinetics can be used as the next generation of catalysts. In this study, molybdenum nitride was synthesized on metal molybdenum substance via an in-situ growth method. The photocatalytic HER rate of Mo3N2 reached 158.78 μmol h(-1) g(-1). Furthermore, the Mo3N2-MoS2/Mo foil was prepared to improve the photoelectrocatalytic performance, showing a 1.5 times enhancement in photocurrent density compared to Mo3N2 alone.