Understanding the high performance of PdSn–TaN(tantalum nitride)/C electrocatalysts for the methanol oxidation reaction: coupling nitrides and oxophilic elements

Abstract

Core–shell like PdSn–TaN(tantalum nitride)/C catalysts with tunable oxophilicity were prepared through a surfactant-free solvothermal method. Optimized Pd₁Sn₃–TaN/C exhibited good activity (3293.46 A g_Pd⁻¹, 15.6 times that of commercial Pd/C), stability and tolerance to CO_ad-like species towards the methanol oxidation reaction (MOR) in alkaline media, which can be ascribed to the interfacial structures and bi-functional effects. Briefly, the core–shell like structure can provide an effective Pd–TaN/C interface related to the large ECSA, and the introduction of Sn can further synergistically modulate the interfacial electronic structures, thereby significantly promoting the MOR performances, as revealed by HRTEM, XPS and electrochemical results. Furthermore, in situ ATR-SEIRAS (attenuated total reflection-surface enhanced infrared absorption spectroscopy) measurements displayed that PdSn–TaN/C went through the dual-channel pathways including a large amount of HCOO_ad and a small amount of CO_ad towards MOR in alkaline medium, which is different from the single CO_ad pathway on commercial Pd/C. Density functional theory (DFT) calculations indicated that the coadsorption intensity and amount of OH provided a chance for CO conversion into CO₂ on Pd₄–SnO₂/TaN(001). Compared to Pd(111), the CO binding energy was evidently reduced on Pd₄–SnO₂/TaN(001). Meanwhile, Pd₁Sn₃–TaN/C also showed high mass activity towards the formic acid oxidation reaction (FAOR) in acidic media, which further confirmed that Pd₁Sn₃–TaN/C may be a promising bi-functional electrocatalyst with high efficiency.