Thiomolybdate [Mo₃S₁₃]^2– Nanoclusters Anchored on Reduced Graphene Oxide-Carbon Nanotube Aerogels for Efficient Electrocatalytic Hydrogen Evolution

Thiomolybdate [Mo₃S₁₃]^2– nanoclusters anchored on reduced graphene oxide-carbon nanotube (rGO-CNTs) aerogels were used as a new catalyst for efficient electrocatalytic hydrogen evolution. The elemental distribution of sulfur (S) corresponded well to the Mo distribution, and both Mo and S elements distributed evenly in the Mo₃S₁₃@rGO-CNTs aerogels. Results indicated that [Mo₃S₁₃]^2– nanoclusters inherently exposed a high number of active edge sites, which greatly improved the electrocatalytic hydrogen evolution. The new peak at 168.8 eV corresponded to the characteristic S–O binding in the S 2p region of Mo₃S₁₃@rGO-CNTs, indicating that the [Mo₃S₁₃]^2– clusters were bond onto the rGO-CNTs aerogels through S–O binding. The strong support of rGO-CNTs aerogels suppressed the aggregation of [Mo₃S₁₃]^2– nanoclusters, exposing more active surface and electrons diffusions on the surface of Mo₃S₁₃@rGO-CNTs aerogels. Mo₃S₁₃@rGO-CNTs aerogels laden with 20 mg of [Mo₃S₁₃]^2– exhibited close hydrogen evolution reaction (HER) performance as compared with that of [Mo₃S₁₃-120]@rGO-CNTs aerogels laden with 120 mg of [Mo₃S₁₃]^2– nanoclusters. This indicated the extremely high HER performance of [Mo₃S₁₃]^2– even at low mass. As a result, Mo₃S₁₃@rGO-CNTs aerogels enabled remarkable electrochemical performances showing a low overpotential (0.179 V at 10 mA cm^–2) with a small Tafel slope, reduced transfer resistance, and excellent stability

Biosorption and Bioreduction of Perchlorate Using the Nano-Fe₃O₄‑Laden Quaternary-Ammonium Chinese Reed: Considering the Coexisting Nitrate and Nano-Fe₃O₄

Nano-Fe₃O₄-laden quaternary-ammonium Chinese reed has been prepared for perchlorate removal, and the laden perchlorate was bioreduced on the surface of the biosorbent by mixed perchlorate-reducing bacteria. Results of kinetics, isotherms, and computations revealed strong competitive impact of coexisting NO₃^– on the uptake of perchlorate. Perchlorate capacity loss dropped significantly (37–50%) at relatively lower molar ratio of nitrate to perchlorate (<5), but 33–46% of the capacity was still retained at a molar ratio of 20. Nitrate laden on the surface of the biosorbent would inevitably inhibit the bioreduction of laden perchlorate. The highest bioreduction rate for laden perchlorate (0.046 mg_p·mg_ss^–1·day^–1) was obtained in the first 24 h of bioreduction. Biofouling on the surface of the biosorbent indicated that small amounts of bacteria and extracellular polymeric substances were possibly still attached on the surface of the biosorbent even after sterilization, which may be a potential cause of the decline in the recovery capacity. The nano-Fe₃O₄ embedded in the biosorbent showed a negligible effect on perchlorate capture but some laden perchlorate (6.5 mg/g) was bioreduced by using the attached nano-Fe₃O₄ as the sole electron donor

Oxygen Vacancy-Dominated Activation of Chlorite and Oxidative Degradation of Sulfamethoxazole

Oxygen vacancy-rich bismuth oxyhalides (BiOX, where X = Cl, Br, I) were successfully synthesized as heterogeneous catalysts for efficiently activating chlorite to produce chlorine dioxide (ClO2) as the prevailing reactive oxidized species (ROS) for sulfamethoxazole (SMX) degradation. Material characterization and density functional theory (DFT) calculations show that BiOI possesses the highest oxygen vacancies, which act as highly active sites. Oxygen vacancies (OVs) not only absorb chlorite but also improve the internal electron conduction efficiency between chlorite and metal ions. The best removal of SMX (84.3%) was achieved under neutral conditions using 70 mg of BiOI and 0.1 mM chlorite. It was discovered that ClO2 is the primary ROS, which was generated via two reactions that involved the formation of HOCl and Bi(IV). The minimal change in acute toxicity and the well-maintained performance in degrading pollutants indicated the potential practical applications of the BiOI/chlorite system. This work reveals a unique mechanism for the OV-mediated activation of chlorite, which highlights the potential advantages of activation via heterogeneous metal oxides BiOX and supplies a new viewpoint for the activation of chlorite for contaminant degradation

rGO/CNTs Supported Pyrolysis Derivatives of [Mo₃S₁₃]^2– Clusters as Promising Electrocatalysts for Enhancing Hydrogen Evolution Performances

Reduced graphene oxide/carbon nanotube (rGO/CNTs) supported [Mo₃S₁₃]^2– clusters and [Mo₃S₁₃]^2– pyrolysis derivatives were synthesized as electrocatalysts for hydrogen production. We investigated the physio-chemical characteristics and electrocatalytic abilities of the [Mo₃S₁₃]^2– clusters and their pyrolysis derivatives. TEM images of pyrolysis derivatives of [Mo₃S₁₃]^2– clusters indicated that some crystalline derivatives were surrounded by the amorphous derivatives at an annealing temperature of 200–270 °C, and some well-crystallized MoS₂ with diameters of 50–100 nm were observed in the pyrolysis derivatives at 500 °C. Both the structure transition and the HER performance of [Mo₃S₁₃]^2– pyrolysis derivatives were mapped in terms of temperature. The atomic ratio of S:Mo significantly decreased from 3.48 to 1.89 as the annealing temperature increased, which indicated the multiple transition forms in pyrolysis derivatives. XPS, XRD, and Raman spectra also indicated the decreased density of edge sites and a poor extent of ordering in the layers of pyrolysis derivatives as the annealing temperature increased. These results corresponded well to the HER activities of the rGO/CNTs macrostructures anchored with different pyrolysis derivatives. The rGO/CNTs anchored with pyrolysis derivatives (annealed at 270 °C) of [Mo₃S₁₃]^2– exhibited an overpotential of ∼178 mV (10 mA cm^–2) with Tafel slope value located at 64.2 mV/dec, which showed relatively higher HER performances than most analogous single-metal molybdenum sulfide nanocomposites. They also exhibited a performance close to those of multimetal nanocomposites