Efficient electrocatalytic CO 2 reduction to ethanol through the proton coupled electron transfer process of PV n Mo (12-n) (n = 1, 2, 3) over indium electrode

The multistep proton-coupled electron transfer (PCET) processes are beneficial for products distribution and selectivity of the electrocatalytic CO reduction reaction (CO RR), which are affected by the nature of the catalyst and electrolyte at electrode-electrolyte interface. Polyoxometalates (POMs) are electron regulators of PCET processes, which can catalyze CO RR effectively. Accordingly, the commercial indium electrodes are combined in this work with a series of Keggin-type POMs (PV Mo O ) , n = 1, 2, 3) to process CO RR with Faradaic efficiency toward ethanol reaching 93.4% at -0.3 V (vs. RHE). The cyclic voltammetry and X-ray photoelectron spectroscopy results reveal the activation of CO molecules by the first PCET process of the V in POM. Subsequently, the PCET process of Mo results the oxidation of the electrode, causing the loss of In active sites. Electrochemical in-situ infrared spectroscopy confirms the weak adsorption of *CO at the later stage of electrolysis due to the oxidation of the In active sites. The indium electrode in PV Mo system retains more In active sites owing to the highest V-substitution ratio, thereby ensuring a high adsorption ratio of *CO and CC coupling. In sum, the regulation of the interface microenvironment by POM electrolyte additives can be used to boost the performance of CO RR.