Pt Nanoparticle Catalyst Modified by MoO ₃ With Rich Oxygen Defects and Its Oxygen Reduction Reaction Performance

An oxygen‐deficient MoO 3 ‐modified carbon black‐supported Pt nanoparticles (NPs) (Pt@MoO 3 /C) catalyst has been synthesized using a solvothermal process. The mean particle size of the well‐dispersed Pt NPs was approximately 1.3 nm. The oxygen vacancies associated with MoO 3 anchored the Pt NPs, thus prevented Pt NPs from oxidation, migration, and aggregation. The catalyst delivered enhanced activity in oxygen reduction reaction (ORR) due to the effective adsorption of reaction intermediates and transfer of hydrogen atoms (H ads ) from Pt sites to MoO 3 sites. At a mass ratio of 2:1(MoO 3 to Pt), the catalyst exhibited an ORR onset potential, half‐wave potential, and limiting current density of 0.986 V, 0.860 V, and −5.9 mA/cm 2 , respectively. In terms of methanol tolerance, the current decay rate was 1/6 of the Pt/C catalyst. First‐principle calculations indicated that the combination of MoO 3 and Pt reduces the overpotential for the rate‐limiting step (conversion of *OH to OH − ) at the Pt site to 0.4 eV, weakening the adsorption of the *OH. In addition, integrating MoO 3 resulted in a downward shift of the Pt d‐band center, which enhanced the interaction between the intermediate 2p orbital and the Pt 5d orbital, significantly increased the oxygen reduction activity on Pt@MoO 3 /C.