Insights into Electrochemical Dehalogenation by Non-Noble Metal Single-Atom Cobalt with High Efficiency and Low Energy Consumption.

It is critical to discover a non-noble metal catalyst with high catalytic activity capable of replacing palladium in electrochemical reduction. In this work, a highly efficient single-atom Co-N/C catalyst was synthesized with metal-organic frameworks (MOFs) as a precursor for electrochemical dehalogenation. X-ray absorption spectroscopy (XAS) revealed that Co-N/C exhibited a Co-N configuration, which had more active sites and a faster charge-transfer rate and thus enabled the efficient removal of florfenicol (FLO) at a wide pH, achieving a rate constant 3.5 and 2.1 times that of N/C and commercial Pd/C, respectively. The defluorination and dechlorination efficiencies were 67.6 and 95.6%, respectively, with extremely low Co leaching (6 μg L), low energy consumption (22.7 kWh kg), and high turnover frequency (TOF) (0.0350 min), demonstrating excellent dehalogenation performance. Spiking experiments and density functional theory (DFT) verified that Co-N was the active site and had the lowest energy barrier for forming atomic hydrogen (H*) (Δ). Capture experiments, electron paramagnetic resonance (EPR), electrochemical tests, and in situ Fourier transform infrared (FTIR) proved that H* and direct electron transfer were responsible for dehalogenation. Toxicity assessment indicated that FLO toxicity decreased significantly after dehalogenation. This work develops a non-noble metal catalyst with broad application prospects in electrocatalytic dehalogenation.