Surface-plasmon-enhanced ethanol electrocatalysis and enhancement mechanism of nanoporous AuPd with wide-spectrum response characteristics under visible light irradiation

Abstract

The plasmonic-enhanced catalytic activity and stability of the ethanol oxidation reaction (EOR) on plasmonic metal materials provides a promising strategy for direct ethanol fuel cells (DEFCs). Most studies are aimed at performance, while only a few studies have provided in-depth discussion of the underlying enhancement mechanism. It is urgent to systematically and thoroughly study the plasmon-enhanced activity and stability of the EOR and the underlying enhancement mechanism. Herein, nanoporous (NP) AuPd was prepared by the dealloying of ternary Au_2.5Pd_2.5Ni₉₅ to thoroughly investigate the effect of visible light irradiation on catalytic performance towards the EOR. UV-vis reflectance spectroscopy indicated that NP AuPd exhibited wide-spectrum response characteristics in the waveband of 400–800 nm. The mass activity (8.5 A mg⁻¹_Pd) of NP AuPd under visible light irradiation of 400–800 nm was almost 1.46 times higher than that of NP AuPd without visible light irradiation (5.8 A mg⁻¹_Pd). The contributions of the solution temperature, photothermal effect, and photoelectric effect to the activity were 17%, 19%, and 10%, respectively. The long-term stability, charge-transfer rate and electrocatalytic kinetics, as well as the antipoisoning ability against CO species, of NP AuPd for the EOR were increased by visible light irradiation. ¹H NMR demonstrated that light irradiation can improve the efficiency of the EOR toward the C2 pathway. In situ-irradiated XPS and ultrafast transient absorption (TA) spectroscopy confirmed hot electron transfer from Au to Pd. Density functional theory (DFT) calculations revealed that AuPd-excited would adsorb OH more easily and CO less readily, and would increase the reaction rate of the EOR via the C2 pathway due to the extra energy from the localized surface plasmon resonance (LSPR) of Au under visible light irradiation.