Molybdenum-based materials have been widely investigated recently as promising alternatives to platinum for catalyzing the hydrogen evolution reaction (HER). Molybdenum carbide is one of the most studied transition-metal carbides because of its cheap price, high abundance, good conductivity, and catalytic activity. In order to further improve the catalytic activity of molybdenum carbide, some modifications have been applied. In this paper, a wide range of magnetic iron-doped molybdenum carbide (Mo2–xFexC) nanomaterials were synthesized by a unique amine–metal oxide composite method. The amount of iron dopants was controlled by setting different iron/molybdenum ratios in the precursors. Iron-doped molybdenum carbide nanomaterials were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, Raman microscopy, and X-ray photoelectron spectroscopy. Electrocatalytic HER tests were used to demonstrate the catalytic activity upon addition ...

Iron-Doped Molybdenum Carbide Catalyst with High Activity and Stability for the Hydrogen Evolution Reaction

Equilibrium adsorption of hydrogen sulfide onto CuO and ZnO

All‐inorganic CsPbI3 perovskite has emerged as an important photovoltaic material due to its high thermal stability and suitable bandgap for tandem devices. Currently, the cell performance of CsPbI3 solar cells is mainly subject to a large open‐circuit voltage (VOC) deficit. Herein, a multifunctional room‐temperature molten salt, dimethylamine acetate (DMAAc) is demonstrated, which not only directly acts as a solvent for precursor solutions, but also regulates the phase conversion process of the CsPbI3 film for high‐efficiency photovoltaics. DMAAc can stabilize the DMAPbI3 structure and eliminate the Cs4PbI6 intermediate phase, which is easily spatially segregated. Meanwhile, a new homogeneous intermediate phase DMAPb(I,Ac)3 is formed, which finally affords high‐quality CsPbI3 films. With this approach, the charge capture activity of defects in the CsPbI3 film is significantly suppressed. Consequently, a VOC of 1.25 V and >21% power conversion efficiency are achieved, which is the record highest reported thus far. This intermediate phase‐regulation strategy is believed to be applicable to other perovskite material systems.

A Versatile Molten‐Salt Induction Strategy to Achieve Efficient CsPbI3 Perovskite Solar Cells with a High Open‐Circuit Voltage >1.2 V

A new technique for sulfide control was investigated in an upflow-anaerobic filter (UAF) treating high-strength, sulfate-rich wastewater. The technique used periodic oxygen injection using oxidation-reduction potential (ORP) as a controlling parameter to regulate oxygen injection. The UAF was operated at a constant influent total-organic carbon of 6740 mg/L but with different influent sulfates of 1000, 3000, and 6000 mg/L. At 1000 and 3000 mg/L influent sulfates, the produced sulfide did not impose any inhibition to methane-producing bacteria (MPB). However, at 6000 mg/L influent sulfate, the produced dissolved sulfide of 804 mg S/L (free sulfide = 280 mg S/L) severely inhibited the methanogenesis, but not the sulfidogenesis. Upon oxygen injection at elevated ORP of -265 mV, sulfides were almost completely eliminated with a concomitant improvement in methane yield by 46%. If oxygenation was excessive because of an oversetting of ORP, the excess oxygen could be used rapidly by facultative heterotrophs, thereby protecting the MPB from oxygen stress. Regarding online sulfide oxidation, it was found that the biogas and injected oxygen needed to pass through an aqueous layer containing trace metals, which were found to have a significant catalytic effect on abiotic sulfide oxidation.

Online oxygen control for sulfide oxidation in anaerobic treatment of high-sulfate wastewater.

Online Oxygen Control for Sulfide Oxidation in Anaerobic Treatment of High Sulfate Wastewater

Low-dimensional (LD) perovskites can effectively passivate and stabilize 3D perovskites for high-performance perovskite solar cells (PSCs). Regards CsPbI3-based PSCs, the influence of high-temperature annealing on the LD perovskite passivation effect has to be taken into account due to fact the black-phase CsPbI3 crystallization requires high-temperature treatment, however, which has been rarely concerned so far. Here, the thermal stability of LD perovskites based on three hydrophobic organic ammonium salts and their passivation effect toward CsPbI3 and the whole device performance, have been investigated. It is found that, phenyltrimethylammonium iodide (PTAI) and its corresponding LD perovskites exhibit excellent thermal stability. Further investigation reveals that PTAI-based LD perovskites are mainly distributed at grain boundaries, which not only enhances the phase stability of CsPbI3 but also effectively suppresses non-radiative recombination. As a consequence, the champion PSC device based on CsPbI3 exhibits a record efficiency of 21.0 % with high stability. 

Temperature‐Reliable Low‐Dimensional Perovskites Passivated Black‐phase CsPbI3 toward Stable and Efficient Photovoltaics

The selective oxidation of hydrogen sulfide to sulfur was studied over iron-molybdenum oxides with various Fe-Mo ratios. Strong synergistic phenomenon in catalytic activity was observed for the Fe-Mo-O binary oxides. Under identical reaction conditions, the areal rates of the binary oxides were superior to those of the corresponding single oxide catalysts, which suggest that the new compound Fe2(MO4)3 formed in the binary oxide is more active than Fe2O3 and MoO3. The oxidation rates of H2S were found to exhibit first-order dependence on the hydrogen sulfide concentration, which implies that the activation of H2S is the rate-limiting step.

Chun-Hsiung Huang

Papers

Temperature‐Reliable Low‐Dimensional Perovskites Passivated Black‐phase CsPbI3 toward Stable and Efficient Photovoltaics

Iron-molybdenum-oxide catalysts for selective oxidation of hydrogen sulfide to sulfur