Metal sulfides such as MoS 2 can serve as co-catalysts to greatly promote the overall efficiency of Fe 2+ -catalyzed advanced oxidation processes (AOPs). Unsaturated S atoms on the surface of metal sulfides can capture protons from the solution to form H 2 S and at the same time expose reductive metallic active sites to greatly accelerate the rate-limiting step of Fe 3+ /Fe 2+ conversion. The significantly enhanced efficiency of H 2 O 2 decomposition makes the AOPs viable for practical applications in the remediation of organic pollutants.

As an important reactive oxygen species (ROS) with selective oxidation, singlet oxygen ( 1 O 2 ) has wide application prospects in biology and the environment. However, the mechanism of 1 O 2 formation, especially the conversion of superoxide radicals (•O 2 − ) to 1 O 2 , has been a great controversy. This process is often disturbed by hydroxyl radicals (•OH). Here, we develop a molybdenum cocatalytic Fenton system, which can realize the transformation from •O 2 − to 1 O 2 on the premise of minimizing • OH. The Mo 0 exposed on the surface of molybdenum powder can significantly improve the Fe 3+ /Fe 2+ cycling efficiency and weaken the production of •OH, leading to the generation of •O 2 − . Meanwhile, the exposed Mo 6+ can realize the transformation ofThe molybdenum cocatalytic effect makes the conventional Fenton reaction have high oxidation activity for the remediation of organic pollutants and prompts the inactivation of Staphylococcus aureus, as well as the adsorption and reduction of heavy metal ions (Cu 2+ , Ni 2+ , and Cr 6+ ). Compared with iron powder, molybdenum powder is more likely to promote the conversion from Fe 3+ to Fe 2+ during the Fenton reaction, resulting in a higher Fe 2+ /Fe 3+ ratio and better activity regarding the remediation of organics. Our findings clarify the transformation mechanism from •O 2 − to 1 O 2 during the Fenton-like reaction and provide a promising REDOX Fenton-like system for water treatment.

Photocatalytic reduction of CO holds great promises for addressing both the environmental and energy issues that are facing the modern society. The major challenge of CO photoreduction into fuels such as methane or methanol is the low yield and poor selectivity. Here, we report an effective strategy to enhance the reduction potential of photoexcited electrons by fluorination of mesoporous single crystals of reduced TiO. Density functional theory calculations and photoelectricity tests indicate that the Ti impurity level is upswept by fluorination, owing to the built-in electric field constructed by the substitutional F that replaces surface oxygen vacancies, which leads to the enhanced reduction potential of photoexcited electrons. As a result, the fluorination of the reduced TiO dramatically increases the CH production yield by 13 times from 0.125 to 1.63 μmol/g·h under solar light illumination with the CH selectivity being improved from 25.7% to 85.8%. Our finding provides a metal-free strategy for the selective CH generation from CO photoreduction.

The greatest problem in the Fe(II)/HO Fenton reaction is the low production of ·OH owing to the inefficient Fe(III)/Fe(II) cycle and the low decomposition efficiency of HO (<30%). Herein, we report a new discovery regarding the significant co-catalytic effect of WS on the decomposition of HO in a photoassisted Fe(II)/HO Fenton system. With the help of WS co-catalytic effect, the HO decomposition efficiency can be increased from 22.9% to 60.1%, such that minimal concentrations of HO (0.4 mmol/L) and Fe (0.14 mmol/L) are necessary for the standard Fenton reaction. Interestingly, the co-catalytic Fenton strategy can be applied to the simultaneous oxidation of phenol (10 mg/L) and reduction of Cr(VI) (40 mg/L), and the corresponding degradation and reduction rates can reach up to 80.9% and 90.9%, respectively, which are much higher than the conventional Fenton reaction (52.0% and 31.0%). We found that the expose reductive W active sites on the surface of WS can greatly accelerate the rate-limiting step of Fe/Fe conversion, which plays the key role in the decomposition of HO and the reduction of Cr(VI). Our discovery represents a breakthrough in the field of inorganic catalyzing AOPs and greatly advances the practical utility of this method for environmental applications.

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