Efficient and selective upcycling of waste polylactic acid into acetate using nickel selenide

The conversion of waste polylactic acid (PLA) plastics into high-value-added chemicals through electrochemical methods is a promising and sustainable approach. However, developing efficient and highly selective catalysts for lactic acid oxidation reaction (LAOR) and understanding the reaction process are challenging. Here, we report the electrooxidation of waste PLA to acetate at a high current density of 100 mA cm−2 with high Faraday efficiency (∼95%) and excellent stability (>100 h) over a nickel selenide nanosheet catalyst. In addition, a total Faraday efficiency of up to 190% was achieved for carboxylic acids, including acetic acid and formic acid, by coupling with the cathodic CO2 reduction reaction. In situ experimental results and theoretical simulations revealed that the catalytic activity center of LAOR was dynamically formed NiOOH species, and the surface-adsorbed SeOx species accelerated the formation of Ni3+ species, thus promoting catalytic activity. The mechanism of lactic acid electrooxidation was further elucidated. Lactic acid was dehydrogenated to produce pyruvate first and then formed CH3CO due to preferential C–C bond cleavage, resulting in the presence of acetate. This work demonstrated a sustainable method for recycling waste PLA and CO2 into high-value-added products.