Environmentally Benign Photoreactions for Hydrogen Production and Cleavage of N═N bond in Azobenzene over Co-Doped Zn(O,S) Nanocatalyst: The Role of In Situ Generated H⁺

Abstract

In this study, fabrication of Co-doped zinc oxysulfide Zn(O,S) solid solution with different amounts of Co (0−10%) was demonstrated for photocatalytic application. It aims to support green energy production and environmental remediation, which have gained increasing attention over the years. Specifically, the as-prepared nanocatalyst was utilized for photocatalytic hydrogen production and hydrogenation reaction. The oxysulfide formation of Zn(O,S) was proved by selected area electron diffraction (SAED), X-ray diffraction (XRD), and diffuse reflectance spectroscopy (DRS) analyses. Briefly, a Co content of 2.5% was found to be the most optimum value for the doping at Zn cation sites in the Zn(O,S) structure, as supported by the results of electrochemical impedance spectroscopy (EIS) and transient photocurrent (TPC) analyses as well as by hydrogen evolution reaction (HER) experiments. In good agreement, 2.5% Co-doped Zn(O,S) exhibited the highest amount of photoevolved hydrogen (H 2 ) under either low-power UV light or solar light illumination, which were 27 000 and 1565 μmol g −1 , respectively. Furthermore, before forming H 2 , the in situ generated proton (H + ) by 2.5% Co-doped Zn(O,S) could be employed for the photocatalytic hydrogenation reaction (PHR) either to cleave the azo bond (NN) in azobenzene or to reduce the nitro group (−NO 2 ) in nitrobenzene. The UV light-induced conversions of AB and NB to aniline were completed within 30 and 120 min, respectively. Finally, the appropriate mechanisms for the HER and PHR, which involve molecular solvation, surface adsorption, molecular pinning, and hydrogenation reactions, are scrupulously proposed and discussed.

Nanostructuring Bi-Doped α-Fe2O3 Thin-Layer Photoanode to Advance the Water Oxidation Performance

“…Besides the photoexcitation process, the adsorption kinetic of water molecules on the photoanode is also crucial. The adsorption can be enhanced when the oxygen vacancy (V O 2 + ) sites are available on material surfaces, as shown in many previous works. − On the basis of the XPS result, BF-5 photoanode exhibited 10.95% V O , which is propitious to the water adsorption during the PEC reaction. The details of water oxidation reaction mechanism without and with Bi dopant on α-Fe 2 O 3 are indicated in Figure a, b, respectively.…”

Recent Developments in Photocatalytic Reduction of Nitro Compounds to Valuable Scaffolds

“…57 Ascorbic acid was used as the hydrogen source and Ru(bpy) 3 Cl 2 as the photosensitizer in the protocol with 4:1 MeOH/H 2 O solvent system under blue LEDs (455 nm) irradiated for 1 h (Scheme 6). 58 fabricated a Co-doped zinc oxysulfide Zn(O,S) photocatalyst via co-precipitation method and used it for the photocatalytic hydrogenation reaction and hydrogen evolution reaction (HER). The 2.5% Co-doped Zn(O,S) catalyst was required for the effective hydrogen photoevolution under low UV or solar irradiation.…”

“…Shuwanto et al 117 have prepared yttrium-doped zinc oxysulfide (Y-Zn (O, S)) solid solution with hydrogen-evolution reaction and Y-doped Zn (O, S) nano catalysts (Scheme 59 ). The synthesized catalyst was then fabricated, characterized, and applied for photocatalytic reduction of nitro compounds for the synthesis of azoarenes in ethanol as sacrificial agent.…”

“…Shuwanto et al (2020) 58 fabricated a Co-doped zinc oxysulfide Zn(O,S) photocatalyst via co-precipitation method and used it for the photocatalytic hydrogenation reaction and hydrogen evolution reaction (HER). The 2.5% Co-doped Zn(O,S) catalyst was required for the effective hydrogen photoevolution under low UV or solar irradiation.…”

Hydrothermic reduction of rutile-ilmenite mineral producing an oxyhydride η-Ti₂FeO_0.2H_2.8: Towards in-situ hydrogen production and storage

“…Recent studies in this direction have used carbohydrate biomass such as glucose and cellulose as carbon source to cause the reduction of metal oxides and salts partly into their metallic forms under hydrothermal conditions of 250°C with and without NaOH (Zhou et al, 2022). Apart from their use as reducing agents for metal oxides, graphene oxide was shown to double the catalytic hydrogen production of ZnO/ZnS using sacrificial reagents that show a trend of efficiencies as follows: ethanol > methanol > isopropanol > ethylene glycol (Gultom et al, 2019).…”