Modulating single-atom Co and oxygen vacancy coupled motif for selective photodegradation of glyphosate wastewater to circumvent toxicant residue

Abstract

The typical wastewater treatment is focused on the photocatalytic efficiency in the degradation of organic pollutants, with little attention to the involved selectivity which may correlate with toxicant residues. Herein, an electron localization strategy for specific O₂ adsorption/activation enabled by photothermal/pyroelectric effect and in situ constructed active centers of single-atom Co and oxygen vacancy (Co-O_V) on the Co/BiOCl-O_V photocatalyst was developed for photocatalytic degradation of glyphosate (GLP) wastewater of high performance/selectivity. Under full-spectrum-light irradiation, a high GLP degradation rate of 99.8% with over 90% C‒P bond-breaking selectivity was achieved within 2 h, while effectively circumventing toxicant residues such as aminomethylphosphonic acid (AMPA). X-ray absorption spectroscopy and relevant characterizations expounded the tailored anchoring of Co single atoms onto the BiOCl-O_V carrier and photothermal/pyroelectric effect. The oriented formation of more ^•O₂⁻ on Co/BiOCl-O_V could be achieved with the Co-O_V coupled center that had excellent O₂ adsorption/activation capacity, as demonstrated by quantum calculations. The formed unique Co-O_V active sites could largely decrease the C‒P bond-breaking energy barrier, thus greatly improving the selectivity toward the initial C‒P bond scission and the activity in subsequent conversion steps in the directional photocatalytic degradation of GLP. The electron localization strategy by in situ constructing the coupled active centers provides an efficient scheme and new insights for the low-toxic photodegradation of organic pollutants containing C‒X bonds.