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.