Photoassisted Electrocatalytic Oxidation of Glycerol to Formic Acid over Heterostructure Cu₂S/Ni₃S₂

The selective electrooxidation of glycerol (GLY) to formic acid is a promising route for biomass valorization, but non-noble catalysts often suffer from poisoning, competitive OH^-/substrate adsorption, and limited light utilization. Herein, we report a sand-rose-like Cu₂S/Ni₃S₂ heterostructure grown on nickel foam, in which cetyltrimethylammonium bromide (CTAB) regulates the Cu₂S morphology and interfacial electronic structure. The resulting catalyst achieves 10 mA cm^-2 at 1.18 V vs RHE for glycerol electrooxidation and maintains a total FE above 90% over five cycles. Under illumination, the formic acid production rate rises from 115.9 to 150.7 μmol cm^-2 h^-1. Combined electrochemical and spectroscopic results indicate that the Cu₂S/Ni₃S₂ heterostructure promotes charge transfer, the CTAB-regulated morphology increases the electrochemically active surface area (ECSA), and illumination improves interfacial reaction kinetics while suppressing the competing oxygen evolution reaction (OER). Operando spectroscopy further suggests that NiOOH is the active oxidizing species and that glycerol is converted to formic acid through sequential oxidation and C-C bond cleavage steps. This work provides an effective strategy for coupling heterostructure engineering and photoassisted electrocatalysis to enhance selective glycerol upgrading.