Hydrothermal carbonation carbon-based photocatalysis under visible light: Modification for enhanced removal of organic pollutant and novel insight into the photocatalytic mechanism

Hydrothermal carbonation carbon (HTCC) is emerging as a promising alternative for photocatalytic removal of contaminants from water. However, the catalytic activity of HTCC is limited by its poor charge transfer ability, and its photocatalytic mechanism remains unclear. Herein, a unique photosensitization-like mechanism was firstly found on Fe modified HTCC (Fe-HTCC) derived from glucose for effective removal of organic pollutants. Under visible light illumination, the organic pollutant coordinated with Fe-HTCC enabled electrons transfer from its highest occupied molecular orbital (HOMO) to conduction band (CB) of Fe-HTCC, which not only oxidized pollutant itself, but also generated oxygen-centered radical for reducing O2 into O2•- towards pollutant removal. The degradation kinetic constant of sulfamethoxazole (SMX) over Fe-HTCC was about 1024.4 and 20.5 times higher than that of HTCC and g-C3N4, respectively. The enhanced performance of Fe-HTCC was originated from dual role of Fe modification: one is to boost the electron-deficient C sites which prefer to coordinate with amino or hydroxyl of pollutants; the other is to enhance the linkage of discrete polyfuran chains in Fe-HTCC for effective electron transfer from pollutant to Fe-HTCC. This work provides new insight into the synthesis and mechanism of HTCC-based high-efficiency photocatalyst for water decontamination.