Hydrogenated titanium dioxide (H-TiO2) nanocrystals were successfully prepared via annealing TiO2 in H2/N2 mixed gas flow at elevated temperatures ranging from 300 to 600 °C. Electron paramagnetic resonance (EPR) spectra were used to determine the produced oxygen vacancy in H-TiO2. Variations in temperature were studied to investigate the concentration change of oxygen vacancy in H-TiO2. The H-TiO2 nanocrystals prepared at different temperatures were employed into photoanodes sensitized by N719 dye and found to have exceptional effect on the solar-to-electric energy conversion efficiency (η). Photoanodes with H-TiO2 nanocrystals hydrogenated at 300 °C show the highest short-circuit current density (Jsc) of 18.92 mA cm(-2) and photoelectrical conversion efficiency of 7.76% under standard AM 1.5 global solar irradiation, indicating a 27 and 28% enhancement in Jsc and η, respectively, in comparison to those with TiO2. The enhancement is attributed to high donor density, narrow band gap and positive shift of flat band energy (Vfb) of H-TiO2 that promote the driving force for electron injection. Intensity-modulated photocurrent spectroscopy (IMPS) accompanied by intensity-modulated photovoltage spectroscopy (IMVS) and other analyses were applied to shed more light on the fundamental mechanisms inside the charge transfer and transport in these systems.

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Choline chloride-based deep eutectic solvents (DESs) exhibited remarkable activity in the cycloaddition of CO2 with propylene oxide (PO) in the absence of any additives under solvent- and metal-free conditions as well as recyclability.

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The use of coupled catalytic systems with ETMs facilitates the reaction process by transporting electrons from catalysts to the oxidant along a low-energy pathway and, finally, DBT was prone to oxidize to DBTO2.

5-Hydroxymethylfurfural (HMF) has been identified as one of the most promising biomass-based multipurpose platform molecules. Innovative protocols, namely electrocatalysis, photocatalysis, and microwave (MW)-assisted chemistry, as well as continuous-flow systems, add a new dimension and another promising toolbox for the oxidation of HMF in recent years. This Minireview deals with recent progress in the catalytic oxidation of HMF to 2,5-furandicarboxylic acid (FDCA) and other intermediates using noble, non-noble, and metal-free systems deploying emerging protocols. Selective HMF downstream oxidation products could be obtained not only via common catalyst modifications, namely nature of the metal, preparative method, and the property of deployed support, but also by using innovative processes.

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