Covalently Connected Nb₄N_5–xO_x–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 Nb₄N_5–xO_x–MoS₂ (0 < x < 1) anchored on N-doped graphene (defined as Nb₄N_5–xO_x–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 Nb₄N_5–xO_x to form fine Nb₄N_5–xO_x–MoS₂ heterostructures, which possess abundant interfaces and fully exposed edge active sites. The as-prepared Nb₄N_5–xO_x–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 Nb₄N_5–xO_x–MoS₂ heterostructures together with chemical coupling of Nb₄N_5–xO_x–MoS₂ and N-doped graphene improve the structural stability and ensure fast electron transfer in the Nb₄N_5–xO_x–MoS₂/NG nanocomposite, further supporting the H₂ generation and stability.