Electronic structure modulation of Pd-MoO_xN_y by controlling surface oxynitride concentration for methanol electroxidation in alkaline media

Direct methanol fuel cells (DMFCs) have gained widespread attention as environmentally friendly energy conversion devices, but the commercialization process still faces many challenges. Among these factors, low catalytic performance and high noble metal content of anode electrocatalysts limits the commercial applications. Based on the oxidation process of CO_ads in the rate-limiting step of alkaline methanol oxidation reaction (MOR), a strategy to accurately regulate the oxygen content of the catalyst was proposed by controlling calcination temperature of transition metal nitride. A series of Pd-MoO_xN_y/C catalysts were designed and constructed. The results showed that Pd-MoO_xN_y/C-2 obtained after calcination at 400 °C showed the highest catalytic activity (3218.75 A·g_Pd⁻¹), kinetic and CO toxicity resistance for MOR. The structural characterizations showed that the nanoparticle size and dispersion of Pd, the surface oxidation degree and oxygen doping ratio of the catalysts significantly changed the electronic structures and surface element composition, altered the d-band centers, which promoted the activation of methanol molecules and intermediates. In a word, catalytic performance for MOR may be precisely controlled by directly controlling the composition and structure of the catalyst surfaces.