Aminated N-doped graphene hydrogel for long-term catalytic oxidation in strong acidic environment

Degradation of phenolic pollutants by persulfate-based advanced oxidation processes: metal and carbon-based catalysis

Wastewater recycling is a solution to address the global water shortage. Phenols are major pollutants in wastewater, and they are toxic even at very low concentrations. Advanced oxidation process (AOP) is an emerging technique for the effective degradation and mineralization of phenols into water. Herein, we aim at giving an insight into the current state of the art in persulfate-based AOP for the oxidation of phenols using metal/metal-oxide and carbon-based materials. Special attention has been paid to the design strategies of high-performance catalysts, and their advantages and drawbacks are discussed. Finally, the key challenges that govern the implementation of persulfate-based AOP catalysts in water purification, in terms of cost and environmental friendliness, are summarized and possible solutions are proposed. This work is expected to help the selection of the optimal strategy for treating phenol emissions in real scenarios.

Advanced Oxidation Processes Based on Sulfate Radicals for Wastewater Treatment: Research Trends

In this work, the recent trends in the application of the sulfate radical-based advanced oxidation processes (SR-AOPs) for the treatment of wastewater polluted with emerging contaminants (ECs) and pathogenic load were systematically studied due to the high oxidizing power ascribed to these technologies. Additionally, because of the economic benefits and the synergies presented in terms of efficiency in ECs degradation and pathogen inactivation, the combination of the referred to AOPs and conventional treatments, including biological processes, was covered. Finally, the barriers and limitations related to the implementation of SR-AOPs were described, highlighting the still scarce full-scale implementation and the high operating-costs associated, especially when solar energy cannot be used in the oxidation systems.

Liquid-Phase Catalytic Exchange of Hydrogen Isotopes over Platinum on Dual-Modified Graphene

Although liquid-phase catalytic exchange is an environmentally friendly treatment of hydrogen isotopes in recycled water of a nuclear power station, the successive development of hydrophobic catalysts is still needed to meet much higher catalytic exchange efficiency and stability. Herein, a dual-modified graphene with Pt loading was designed by amination and silanization to anchor Pt nanoparticles uniformly, as well as obtain higher hydrophobicity. After coating the reactor walls with poly(dimethylsiloxane), the catalytic exchange efficiency of the dual-modified graphene with lower Pt loadings (Pt/200-S-NH₂-GR) improved up to 91% at 80 °C, which was higher than 80% of only animated graphene (Pt/NH₂-GR) at the same condition. Furthermore, the Pt/200-S-NH₂-GR maintained high stability for at least 10 h in the temperature range of 40-80 °C, while the Pt/NH₂-GR decreased 17% of catalytic exchange efficiency at 80 °C within 10 h. Using the dual-modified strategy for graphene support, high efficiency and stability was achieved for heavy water dedeuteration.

Nitrogen-carbon materials base on pyrolytic graphene hydrogel for oxygen reduction

HYPOTHESIS

Oxygen reduction reaction (ORR) has played a significant role in the utilization of energy nowadays. Nitrogen-doped carbon materials are seen as promising catalysts for ORR, so it is of great significance in studying the functions of different nitrogen moieties.

EXPERIMENTS

The graphene hydrogel-based nitrogen-arbon materials (GH N-C) were fabricated by first obtaining a gel through hydrothermal treatment using graphene oxide (GO) as precursor, and then calcined in an ammonia atmosphere at different temperatures to form N-doped graphitized materials with divers nitrogen configuration.

FINDINGS

GH N-C materials with tunable nitrogen configuration were synthesized by a two-step method base on graphene hydrogel. Benefiting from the 3D hydrogel structure, rich defects and optimized chemical properties, GH N-C-900 prepared by NH₃ pyrolysis at 900 °C exhibits an excellent electrocatalytic performance toward ORR, with the onset potential of 0.947 ± 0.013 V versus RHE, half-wave potential of 0.830 ± 0.010 V versus RHE, electron transfer number of 3.61-3.99, along as methanol tolerance and superior long-term stability. Comprehensive studies have shown that there is a positive correlation between the total amount of pyrrolic-N and quaternary-N and the catalytic performance of ORR.