RESUMO
Atomically dispersed CoNC is a promising material for H2 O2 selective electrosynthesis via a two-electron oxygen reduction reaction. However, the performance of typical CoNC materials with routine CoN4 active center is insufficient and needs to be improved further. This can be done by fine-tuning its atomic coordination configuration. Here, a single-atom electrocatalyst (Co/NC) is reported that comprises a specifically penta-coordinated CoNC configuration (OCoN2 C2 ) with Co center coordinated by two nitrogen atoms, two carbon atoms, and one oxygen atom. Using a combination of theoretical predictions and experiments, it is confirmed that the unique atomic structure slightly increases the charge state of the cobalt center. This optimizes the adsorption energy towards *OOH intermediate, and therefore favors the two-electron ORR relevant for H2 O2 electrosynthesis. In neutral solution, the as-synthesized Co/NC exhibits a selectivity of over 90% over a potential ranging from 0.36 to 0.8 V, with a turnover frequency value of 11.48 s-1 ; thus outperforming the state-of-the-art carbon-based catalysts.
RESUMO
Magnetic 0.9NiFe2O4/0.1SiO2 nanocomposites were successfully prepared via a rapid combustion process, and the morphology and magnetic properties of them were investigated by TEM, XRD, VSM, and BET techniques. The magnetic 0.9NiFe2O4/0.1SiO2 nanocomposites calcined at 400 °C for 2 h with absolute alcohol of 20 mL were characterized with the average particle size of about 28 nm and the specific magnetization of 192.0 Am2/kg. The magnetic 0.9NiFe2O4/0.1SiO2 nanocomposites were employed to remove methylene blue (MB) from aqueous solutions, the adsorption kinetics and adsorption isotherm of MB onto 0.9NiFe2O4/0.1SiO2 nanocomposites at room temperature were investigated, and the regression equations were found in good agreement with the pseudo-second-order model in the initial MB concentrations of 100-600 mg/L; the adsorption equilibrium data of MB onto 0.9NiFe2O4/0.1SiO2 nanocomposites at room temperature were analyzed with Langmuir, Freundlich and Redlich-Peterson models, and the adsorption isotherm was most effectively described by the Redlich-Peterson model based on the value of the correlation coefficient (0.9810).
RESUMO
The efficient and ecofriendly removal of pharmaceutical antibiotics and heavy metal Cr(VI) from water sources is a crucial challenge in current environmental management. Photocatalysis presents a viable environmentally friendly solution for eliminating organic contaminants and heavy-metal ions. In this study, a novel S-scheme CuInS2/ZnIn2S4 (CIS/ZIS) heterojunction was developed using a one-pot solvothermal method. The optimized CIS/ZIS heterojunction exhibited considerably improved photocatalytic activity for the removal of antibiotics and Cr(VI), achieving over 90% removal for both tetracycline hydrochloride (TC) (20 mg/L) and Cr(VI) (20 mg/L) under visible light irradiation. The study also delved into the effect of coexisting inorganic anions and assessed the cyclic stability of the composite photocatalysts. This enhancement mechanism can be delineated into three key elements. First, the incorporation of the narrow-gap semiconductor CuInS2 effectively augmented the photoabsorption capacity. Second, the inclusion of ZnIn2S4 caused an increase in surface active sites. Most importantly, the internal electric field at the interface between CuInS2 and ZnIn2S4 expedited the separation of photogenerated carriers. Furthermore, the results revealed that superoxide radical and photogenerated holes are the primary active substance responsible for TC removal, while photogenerated electrons play a central role in the photoreduction of Cr(VI). To gain insights into the transport pathways of photogenerated carriers, we conducted experiments with nitrotetrazolium blue chloride (NBT) and photodeposited gold. This study offers an innovative approach to enhancing the photocatalytic performance of ternary In-based materials by constructing S-scheme heterojunctions.