Hydrogen-evolved Dy-doped Zn(O,S) photocatalysts with different amounts of Dy precursor have been synthesized, characterized and further utilized for hydrogenation reactions. The Dy catalysts are first examined using electrochemical impedance spectroscopy, photo responsivity, and the hydrogen evolution reaction. Dy-doped Zn(O,S) with 10% Dy precursor shows the best photocatalyst performance with the highest H2 production rate of 8.160 mmol g−1 h−1. This catalyst is chosen for conducting the hydrogenation reaction. It is our intention to confirm the correlation between the photocatalytic H2 production rate and the hydrogenation reactions of 4-nitrophenol to 4-aminophenol and azobenzene to aniline, which is a step further in the hydrogenation reaction to challenge the NN bond cleavage of azobenzene. A 100% photo conversion of 60 ppm azobenzene to aniline in 6 h was confirmed under a low-power UV light illumination in a 10% ethanol solution. Kinetic steps and kinetic mechanisms are proposed, which involve the important reaction steps of solvation, adsorption, pinning, and surface hydrogenation reaction operating together.
As an environmentally friendly and sustainable method for ammonia synthesis, nitrogen reduction reaction (NRR) by electrocatalysis possesses several advantages, including viability under mild conditions, abundant reaction raw materials and low energy consumption, and thus it is supposed to be a promising alternative to the traditional Haber–Bosch process. However, the stable NN bonds in the nitrogen (N2) and the competing hydrogen evolution reaction (HER) put harsh requirements on catalysts. In this study, the CoS/MoS2 heterojunction catalyst where CoS nanoparticles are anchored on the MoS2 nanosheets is reported as a high-efficiency NRR catalyst. The catalysts have high NH3 yield (23.23 μg h−1 mgcat.−1), reasonable faradaic efficiency (FE, 12.63%) and long-term electrochemical stability under −0.45 V vs. RHE in 0.1 M Na2SO4 solution, whose performance is better than MoS2 and CoS. The TPV results show rapid interfacial electron transfer and good conductivity of the material, and the DFT calculation reveals that the CoS attached to the (100) plane effectively enhances N2 adsorption and catalysis performance.
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