Engineering pathway control in single-atom catalysis for advanced oxidation and electro-oxidation water treatment

Abstract

Carbon-supported single-atom catalysts (SACs) are emerging as a credible platform for water purification because their coordination microenvironments can be engineered to couple oxidant activation with pathway selectivity. This review reframes SAC-enabled advanced oxidation processes (AOPs) and electro-AOPs from activity-centric benchmarking to pathway-centric control, emphasizing how anchoring motifs (M–N_x, defect/edge trapping, paired sites) and first-/second-sphere regulation steer radical (˙OH/SO₄˙⁻/O₂˙⁻) versus nonradical (e.g., ¹O₂, surface complexes, electron transfer) routes and thereby govern oxidant utilization, matrix tolerance, and by-product risk. We highlight persistent “credibility gaps” that limit translation—misassigned reactive species arising from overinterpreted quenchers/probes/EPR, dynamic site reconstruction and carbon corrosion under oxidative or polarized conditions, and pathway collapse in real waters containing chloride, bicarbonate, and natural organic matter. To address these bottlenecks, we propose an evidence hierarchy and a minimum reporting set spanning site identity/density, leaching and homogeneous controls, long-duration stability with structural verification, real-water stress tests, energy-normalized electro-AOP metrics, and transformation product/toxicity endpoints. Collectively, these guidelines connect atomic-scale design to defensible, scalable oxidation chemistry.