Modulating the interfacial built-in electric field in oxygen vacancies-enriched Ru/MxOy@C (M = V, Nb, Ta) ordered macroporous heterojunctions for electrocatalytic hydrogen production

[Display omitted] •The difference in Fermi level between Ru and MxOy results in electron transfer.•The BEF created by the charge transfer facilitates the transfer of the charge.•The electronic structure of Ru was regulated by MxOy.•The interaction between Ru and MxOy improves the stability and activity of Ru.•The porous structure of the catalysts promotes the diffusion of electrolyte. The differences in Fermi levels (Ef) can drive the electrons flow across the metal/semiconductor interfaces, resulting in a built-in electric field (BEF) to enhance charge migration. Meanwhile, the induced electron-rich/deficient counterparts can modulate the active sites and reaction steps. In this work, a three-dimensionally ordered macroporous (3DOM) heterostructure with oxygen vacancy (Ov) supported by carbon (Ru/MxOy@C, M = V, Nb, Ta) was fabricated. Since the Ef of MxOy is higher than that of Ru, an adjustable BEF directed by MxOy towards Ru is generated at the interface. The electron-deficient MxOy can dissociate H2O effectively, and the electron-rich Ru favors the desorption of hydrogen intermediates. Both experimental and theoretical results confirm the above conclusions. The Ru/Ta2O5@C demonstrates superior activity than Pt/C. This work provides new design principles toward efficient electrocatalysts for hydrogen evolution reaction (HER).