Electrochemical Conversion of Alcohols into Acidic Commodities on Nickel Sulfide Nanoparticles

The electrocatalytic oxidation of alcohols is a potentially cost-effective strategy for the synthesis of valuable chemicals at the anode while simultaneously generating hydrogen at the cathode. For this approach to become commercially viable, high-activity, low-cost, and stable catalysts need to be developed. Herein, we demonstrate an electrocatalyst based on earth-abundant nickel and sulfur elements. Experimental investigations reveal the produced NiS displays excellent electrocatalytic performance associated with a higher electrochemical surface area (ECSA) and the presence of sulfate ions on the formed NiOOH surface in basic media. The current densities reached for the oxidation of ethanol and methanol at 1.6 V vs reversible hydrogen electrode (RHE) are up to 175.5 and 145.1 mA cm^-2, respectively. At these high current densities, the Faradaic efficiency of methanol to formate conversion is 98% and that of ethanol to acetate is 81%. Density functional theory calculations demonstrate the presence of the generated sulfate groups to modify the electronic properties of the NiOOH surface, improving electroconductivity and electron transfer. Besides, calculations are used to determine the reaction energy barriers, revealing the dehydrogenation of ethoxy groups to be more favorable than that of methoxy on the catalyst surface, which explains the highest current densities obtained for ethanol oxidation.