An efficient, simple, and inexpensive N, S-co-doped hydrochar (SNHC) was synthesized from waste straw by a one-pot hydrothermal process without calcination for the removal of Cr(VI). SNHC demonstrated excellent adsorption performance for Cr(VI) and high stability, achieving a high capacity of 171.33 mg/g (293 K, pH 2) and a capacity retention of 82.73 % after five cycles. The adsorption behavior was determined as a multilayer adsorption process based on chemisorption according to the simulation the results of Freundlich adsorption isotherms and pseudo-second-order models. The characterization of SNHC revealed that graphite N and thiophene S formed by the material were the effective active sites, functioning as electron donors to contribute a significant amount of electrons to reduce Cr(VI) to Cr(III). Therefore, next to electrostatic adsorption and complexation, the synergistic reduction of Cr(VI) by graphite N and thiophene S was the main mechanism for Cr(VI) removal. Additionally, density functional theory calculations indicated a low adsorption energy of thiophene S, which increased the attractive interaction between SNHC and Cr(VI) and played the most important role in reducing Cr(VI). The mechanism of the effect of graphite N and thiophene S on Cr(VI) removal not only offered a comprehensive perspective on the role of N, S co-doped mediation in hydrochar but also provided the basic theory for its practical application.
Solution-processed graphene oxide (GO) films have tremendous potential in the applications of transparent electrodes. The mechanism of how the GO film is reduced by reducing gas has not been clarified because the reducing gas cannot permeate through the plane of GO. Here, an effective
chemical and thermal synergy reduction of GO film was investigated. We also revealed how the reducing gas permeates through the GO film barrier. The GO film was chemically reduced by the vapor of hydriodic acid and acetic acid (HI–AcOH, volume ratio of 1:1) at 100 °C for 3 h, followed
by annealing at 1100 °C for 0.5 h in an Ar atmosphere. The reduced graphene oxide (RGO) film had a sheet resistance of 562 Ω/〈 and a transparency of 63.7% at a typical wavelength of 550 nm, which is sufficient for many applications in optoelectronics, and this effective synergy
reduction method advances the research on graphene-based electrodes.
Yonghui Yang,Hengwei Yan,Zhanwei Liu,Shenghui Guo,Wenhui Ma,Mingyi Hu,Rui Xia,Wenrong Wang
This study explores a CaO-regulated thermal–electrochemical synergistic reduction approach for TiO 2 in fluoride-based molten salts, aiming to enhance deoxygenation efficiency and particle densification. At elevated temperatures, CaO reacts with TiO 2 and the NaF–K 2 TiF 6 molten salt to form CaF 2 and reactive intermediate phases, which facilitate the in situ generation of metallic Ca and alter the local redox environment. These transformations promote the complete electrochemical reduction of TiO 2 into metallic titanium through the formation and subsequent reduction of titanium oxyfluoride complexes such as K 2 NaTiOF 5 and TiOF 2 . Cyclic voltammetry reveals that CaO addition induces a negative shift in the Ti(IV)/Ti(III) redox potential, suggesting a modified reduction pathway and increased activation energy. The titanium powders synthesized at 890 °C with current densities ranging from 2.0 to 3.5 A/cm 2 exhibit reduced oxygen content down to 2900 ppm and a dense, near-spherical morphology. Microstructural analyses using FIB–SEM and EDS confirm that CaO incorporation suppresses surface oxidation and promotes particle uniformity. These findings provide mechanistic insight into the synergistic role of CaO in titanium deoxygenation and demonstrate its potential in reducing the oxygen content of titanium powders and improving their compositional uniformity.
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