Transformation of biomass and plastic wastes to value-added
chemicals
and fuels is considered an upcycling process that is beneficial to
resource utilization. Electrocatalysis offers a sustainable approach;
however, it remains a huge challenge to increase the current density
and deliver market-demanded chemicals with high selectivity. Herein,
we demonstrate an electrocatalytic strategy for upcycling glycerol
(from biodiesel byproduct) to lactic acid and ethylene glycol (from
polyethylene terephthalate waste) to glycolic acid, with both products
being as valuable monomers for biodegradable polymer production. By
using a nickel hydroxide-supported gold electrocatalyst (Au/Ni(OH)2), we achieve high selectivities of lactic acid and glycolic
acid (77 and 91%, respectively) with high current densities at moderate
potentials (317.7 mA/cm2 at 0.95 V vs RHE and 326.2 mA/cm2 at 1.15 V vs RHE, respectively). We reveal that glycerol
and ethylene glycol can be enriched at the Au/Ni(OH)2 interface
through their adjacent hydroxyl groups, substantially increasing local
concentrations and thus high current densities. As a proof of concept,
we employed a membrane-free flow electrolyzer for upcycling triglyceride
and PET bottles, attaining 11.2 g of lactic acid coupled with 9.3
L of H2 and 13.7 g of glycolic acid coupled with 9.4 L
of H2, respectively, revealing the potential of coproduction
of valuable chemicals and H2 fuel from wastes in a sustainable
fashion.
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