Construction of directional electron transfer from Pt to MoO2-x in macroporous structure for efficient hydrogen oxidation

Abstract

Hydrogen oxidation reaction (HOR) as the anode reaction in proton exchange membrane fuel cell, usually suffers from the high loading of platinum (Pt) and subsequent CO poisoning especially by using industrial crude hydrogen as fuel. In this work, we propose a directional electron transfer route from Pt to MoO_2-x in the macroporous structure to significantly enhance the HOR activity as well as the CO tolerance, which is constructed by interface engineering and defect strategy to anchor highly dispersed Pt nanoparticles onto the three-dimensional MoO_2-x-C framework. The optimized 2Pt-MoO_2-x-C with 1.02 wt% Pt demonstrates higher HOR peak current density (3.57 mA cm⁻²) and nearly 25 times higher mass activity than 20 wt% Pt/C. The excellent HOR performance is attributed to the synergistic effect between Pt and MoO_2-x species, in which the charge transfer from Pt to MoO_2-x improves H₂ adsorption ability of Pt and accelerates the activation of H₂ due to the reduced hydrogen binding energy of MoO_2-x caused by Pt-O construction, leading to the release of H* thereby the enhancement of HOR activity. The construction of three-dimensional macroporous structure enhances the HOR dynamics by promoting the conductivity, mass transfer and the exposure of active sites. Moreover, the formed Mo-OH in Pt-MoO_2-x-C can effectively react with CO species to remove the CO poisoning of Pt, endowing the excellent CO tolerance.