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Water pollution caused by dye is a serious challenge. Herein, we use a novel discharge process to functionalize carbon nanotube (CNT) by COOH groups to form CNT30 for removing methyl red (MR) from water. By pristine CNT, 75% MR is removed in 60 min, with an adsorption capacity of 68.44 mg g-1. By CNT30, 85% MR is fast removed in only 5 min, and the removal efficiency reaches to 95% after 30 min, with an adsorption capacity of 80.33 mg g-1. Thus, a higher MR removal efficiency is achieved in a much shorter time on CNT30. Moreover, CNT30 has an outstanding reusability, with the MR removal efficiency decreasing by only 7% after ten cycles. The COOH groups on CNT30 improve the hydrophilicity of CNT30, thus promoting the interaction of MR in water with CNT30. The hydrogen bonding and electrostatic interaction of MR with the COOH groups on CNT30 could be the force to drive MR adsorption on CNT30. The higher COOH content could be the origin for the better performance of CNT30 in removing dye from water. The discharge process developed herein is operated in O2, without using harmful substances, and the COOH content on CNT can be efficiently tuned by simply changing discharge time. This is different from the chemical modification widely used to functionalize CNT by strong oxidants, e.g., HNO3. The present work is of great significance to realize green construction of materials for more efficiently removing dye from water.

Carbon-based materials, metal oxides and metal nanoparticles have been widely used in propellants, explosives and pyrotechnics. Cold plasma technique has been developed for material fabrication and modification at temperatures lower than 200 ⁰C. Due to the low temperatures, cold plasma can efficiently modify material surface properties, and simultaneously maintain material structures well, especially for temperature-sensitive materials. Cold plasma applies gas, e.g. Ar, N2, O2, H2 and air, as working gas, without any harmful substance like acid, alkali and organic solvent. Moreover, material surface properties can be efficiently tuned by simply changing plasma properties, e.g. power, time and working gas. The present review discusses recent progresses in using cold plasma to fabricate carbon-based materials, metal oxides and metal nanoparticles, and to modify surface properties of carbon-based materials, metal oxides and metal nanoparticles. Future research opportunities and challenges are also proposed. It is believed that the present review will stimulate more studies on material fabrication and modification by cold plasma, and help to construct more efficient materials for propellants, explosives and pyrotechnics.

Photocatalytically reducing CO2 by H2O into valuable carbon-containing chemicals is one of the greatest concerns for both scientific and industrial communities, due to its great potential in solving energy and environmental problems. However, the photocatalytic reduction efficiency is still much lower than the need of large-scale applications. Abilities of photocatalysts in adsorbing CO2 and splitting H2O to produce protons are crucial factors determining the photocatalytic reduction efficiency. Significant research efforts have been devoted to addressing the issues on CO2 adsorption and proton production. The present review discusses the recent progresses in improving CO2 adsorption and proton production on photocatalysts for increasing the photocatalytic reduction efficiency. Future research opportunities and challenges are also discussed. It is hoped that the present review can stimulate more deep insights on adsorption of CO2 and production of proton for increasing the photocatalytic reduction efficiency.