Dual Modulation of Bulk Electronic Structure and Surficial Active Sites in Sea Urchin‐Like MoO ₂ Nanoreactors Promoting Electrocatalytic Hydrogen Evolution

Abstract Electrocatalytic hydrogen evolution reaction (HER) is a promising strategy for realizing carbon neutralization as well as for the production of green hydrogen. Molybdenum dioxide (MoO 2 ), possesses acid corrosion resistance and near‐metal‐level conductivity, endowing its widespread application in acidic HER. However, due to spatial barriers at the edge of sites and weak H * adsorption, the HER activity of MoO 2 is greatly limited. Herein, a sea urchin‐like Pt@N‐MoO 2 nanoreactor is designed, in which the bulk electronic structure and surface‐active sites are modulated by N doping and Pt single atoms anchoring, respectively. DFT calculations indicate that Mo─N coupling changes the charge density of Mo atoms, enhances the adsorption of H * , and thus optimizes the Gibbs free energy. The appearance of Pt‐O/N sites compensates for the lack of active sites exposed by MoO 2 , while promoting the desorption of H 2 from the catalyst surface and accelerating the HER process. This work provides an effective strategy for activating inert electrocatalysts to promote energy conversion via a dual modulation strategy of bulk and surface engineering.