Covalently Connected Nb₄N5–xOx–MoS₂ Heterocatalysts with Desired Electron Density to Boost Hydrogen Evolution

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 Nb 4 N 5– x O x –MoS 2 (0 < x < 1) anchored on N-doped graphene (defined as Nb 4 N 5– x O x –MoS 2 /NG) is synthesized by hydrothermal and chemical vapor deposition (CVD) approaches. During the CVD process, MoS 2 nanosheets are etched into small pieces and covalently interconnected with Nb 4 N 5– x O x to form fine Nb 4 N 5– x O x –MoS 2 heterostructures, which possess abundant interfaces and fully exposed edge active sites. The as-prepared Nb 4 N 5– x O x –MoS 2 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 Nb 4 N 5– x O x –MoS 2 heterostructures together with chemical coupling of Nb 4 N 5– x O x –MoS 2 and N-doped graphene improve the structural stability and ensure fast electron transfer in the Nb 4 N 5– x O x –MoS 2 /NG nanocomposite, further supporting the H 2 generation and stability.