Covalently Connected Nb₄N_5–<i>x</i>O_<i>x</i>–MoS₂ Heterocatalysts with Desired Electron Density to Boost Hydrogen Evolution

Abstract

Rational design and controllable synthesis of efficient and robust electrocatalysts for hydrogen evolution reaction (HER) remain a critical challenge for the renewable energy economy. Herein, heterostructured Nb4N5–xOx–MoS2 (0 < x < 1) anchored on N-doped graphene (defined as Nb4N5–xOx–MoS2/NG) is synthesized by hydrothermal and chemical vapor deposition (CVD) approaches. During the CVD process, MoS2 nanosheets are etched into small pieces and covalently interconnected with Nb4N5–xOx to form fine Nb4N5–xOx–MoS2 heterostructures, which possess abundant interfaces and fully exposed edge active sites. The as-prepared Nb4N5–xOx–MoS2 heterostructures with Nb–(N,S)–Mo bridges provide desired electron density, which exhibit excellent chemisorption ability for both H and water, significantly improving the intrinsic HER activity. Meanwhile, the covalently connected Nb4N5–xOx–MoS2 heterostructures together with chemical coupling of Nb4N5–xOx–MoS2 and N-doped graphene improve the structural stability and ensure fast electron transfer in the Nb4N5–xOx–MoS2/NG nanocomposite, further supporting the H2 generation and stability.