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 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.