Porous PdWM (M = Nb, Mo and Ta) Trimetallene for High C1 Selectivity in Alkaline Ethanol Oxidation Reaction.

Abstract

Direct ethanol fuel cells are among the most efficient and environmentally friendly energy‐conversion devices and have been widely focused. The ethanol oxidation reaction (EOR) is a multielectron process with slow kinetics. The large amount of by‐product generated by incomplete oxidation greatly reduces the efficiency of energy conversion through the EOR. In this study, a novel type of trimetallene called porous PdWM (M = Nb, Mo and Ta) is synthesized by a facile method. The mass activity (15.6 A mgPd −1) and C1 selectivity (55.5%) of Pd50W27Nb23/C trimetallene, obtained after optimizing the compositions and proportions of porous PdWM, outperform those of commercial Pt/C (1.3 A mgPt −1, 5.9%), Pd/C (5.0 A mgPd −1, 7.2%), and Pd97W3/C bimetallene (9.5 A mgPd −1, 14.1%). The mechanism by which Pd50W27Nb23/C enhances the EOR performance is evaluated by in situ Fourier transform infrared spectroscopy and density functional theory calculations. It is found that W and Nb enhance the adsorption of CH3CH2OH and oxophilic high‐valence Nb accelerates the subsequent oxidation of CO and —CH x species. Moreover, Nb promotes the cleavage of C—C bonds and increases the C1 selectivity. Pd60W28Mo12/C and Pd64W27Ta9/C trimetallene synthesized by the same method also exhibit excellent EOR performance.