Co0.9Co0.1S Nanorods with an Internal Electric Field and Photothermal Effect Synergistically for Boosting Photocatalytic H2 Evolution.

The paper reports a strategy to synthesize Cd0.9Co0.1S nanorods (NRs) via a one-pot solvothermal method. Remarkably, the pencil-shaped Cd0.9Co0.1S NRs with a large aspect ratio and good polycrystalline plane structure significantly shorten the photogenerated carrier transfer path and achieve fast separation. An appropriate amount of Co addition enhances visible light-harvesting and generates a photothermal effect to improve the surface reaction kinetics and increases the charge transfer rate. Moreover, the internal electric field facilitates the separation and transfer of carriers and effectively impedes their recombination. As a result, the optimized Cd0.9Co0.1S NRs yield a remarkable H2 evolution rate of 8.009 mmol·g-1·h-1, which is approximately 7.2 times higher than that of pristine CdS. This work improves the photocatalytic hydrogen production rate by tuning and optimizing electronic structures through element addition and using the photothermal synergistic effect.

Two Co(II)/Ni(II) complexes based on nitrogenous heterocyclic ligands as high-performance electrocatalysts for the hydrogen evolution reaction.

Two transition metal complexes {[Co2(bpda)4(H2O)2]·4H2O}n(Co-1) and {[Ni(bpda)2(H2O)2]·2H2O}(Ni-2) (H2bpda = 2,2'-bipyridine-4,4'-dicarboxylic acid) have been synthesized by a hydrothermal method and characterized. These two compounds can be explored as stable electrocatalysts in the hydrogen evolution reaction (HER) using two important parameters: the overpotential and Tafel slope (TS). Electrochemical studies suggest that the reaction kinetics of a Co-1 catalyst is more favorable than that of a Ni-2 catalyst. Co-1 exhibits better HER performance with an overpotential of 182 mV at a current density of 10 mA cm-2, a small TS of 87.21 mV dec-1 and superior long-term durability (of up to 3000 cycles). Structural analysis shows that its catalytic activity is improved due to the two mixed valence cobalt ions and the pore structure formed by hydrogen bonds in Co-1, which is different from that of Ni-2. In addition, the mechanism of the HER is also explained theoretically by DFT molecular orbital and free energy calculations in this article.

NO reduction with CO over a highly dispersed Mn/TiO2catalyst at low temperature: a combined experimental and theoretical study.

A highly dispersed Mn/TiO2catalyst, which has high efficiency for NO conversion with CO and almost completed N2selectivity at a low-temperature range (350-550 K), was investigated using experimental and DFT theoretical calculation. The characterization results illustrated that the catalyst assembled with nanoparticles and the Mn doping into the TiO2surface lattice led to the formation of Mn-O-Ti configuration, which enhanced the dispersion of Mn on the body of TiO2. The DFT study mapped out the complete catalytic cycle, including reactants adsorption, oxygen vacancy generation, N2O intermediates formation, N2formation in Eley-Rideal (ER), Langmuir-Hinshelwood, and termolecular Eley-Rideal mechanisms. With thermodynamic and kinetic analysis combined with experimental results, the ER reaction process was considered to be the fundamental mechanism over the highly dispersed Mn/TiO2catalyst. The calculation results indicated that N2O was a significant intermediate. However, the rapid N2O reduction process led to high N2selectivity. The rate-limiting step was the deoxygenation step of NO-MnOv/TiO2from N-O bond scission. The active site Mn-Ovpair embedded in Mn/TiO2was responsible not only for the formation of N-Mn/TiO2in the ER-1 step but also for the N2O deoxygenation process to make the final product N2in the ER-2 step. The synergetic effect between Mn 3d electron and the oxygen vacancy of TiO2were responsible for the catalytic activity of Mn/TiO2.