Yi Liu,Yongjin Ma,Wenwen Liu,Yanyang Shang,Anquan Zhu,Pengfei Tan,Xiang Xiong,Jun Pan
As the highest energy facet of wurtzite CdS, (0 0 2) facet is well worth investigating toward the contribution in photocatalytic hydrogen (H 2 ) evolution. In this study, flower-like CdS with highly preferred (0 0 2) facet was fabricated through a low temperature mixed-solvothermal strategy. The mixted-solvent of diethylenetriamine (DETA) and ethyl alcohol (EtOH) was used to inhibit the growth of (1 0 0) and (1 0 1) facets. For comparison, porous flower-like, belt-like and net-like CdS samples with different preferred degrees of (0 0 2) facet were controllably synthesized by the addition of H 2 O in different proportions. The preferred orientation degrees of (0 0 2) facet were qualitative proved by the mathematical fitting of XRD patterns. As expected, the flower-like CdS exhibited the highest photocatalytic activity on H 2 evolution under visible light without any co-catalyst. Meanwhile, the photocatalytic H 2 production increased with the increasement of exposed (0 0 2) facet, which suggested that (0 0 2) facet of CdS played a critical role in improving the photocatalytic activity. Moreover, the growth mechanisms of CdS with various morphologies were investigated and proposed in detail.
Exploring efficient photocatalysts to facilitate water splitting into green hydrogen (H 2 ) energy is of great significance nowadays. In this work, we successfully synthesized CdS nanoflowers coated by zero-dimensional MMoS 4 (M = Ni, Co, Cu) cocatalysts using a mild two-pot solvothermal method. Notably, 2.5%-NiMoS 4 /CdS catalyst exhibits optimal photocatalytic H 2 evolution from benzyl alcohol aqueous solution under visible-light irradiation, and its photocatalytic H 2 activity (7269.5 μmol·h −1 ·g −1 ) is 10.1 times higher than that of pure CdS (716.6 μmol·h −1 ·g −1 ). Simultaneously, benzyl alcohol can be synergistically converted into benzaldehyde after dehydrogenation . Such excellent photocatalytic performance mainly benefits from the existence of an internal electric field (IEF), which is demonstrated by experimental analysis and density functional theory calculations. And the IEF greatly accelerates the separation of electron-hole pairs during the photocatalytic H 2 evolution process.
Unspecific peroxygenases exhibit high activity for the selective oxyfunctionalization of inert C(sp 3 )-H bonds using only H 2 O 2 as a clean oxidant, while also exhibiting sensitivity to H 2 O 2 concentration. CdS-based semiconductors are promising for the photosynthesis of H 2 O 2 owing to their adequately negative potential for oxygen reduction reaction via a proton-coupled electron transfer process, however, they suffer from fast H 2 O 2 decomposition on the surface of pristine CdS. Therefore, [Cp*Rh(bpy)H 2 O] 2+ , a highly selective proton-coupled electron transfer catalyst, was anchored onto a supramolecular polymer-grafted CdS nanoflower to construct an efficient integrated photocatalyst for generating H 2 O 2 , mitigating the surface issue of pristine CdS, increasing light absorption, accelerating photonic carrier separation, and enhancing oxygen reduction reaction selectivity to H 2 O 2 . This photocatalyst promoted the light driven H 2 O 2 generation rate up to 1345 µmol·L −1 ·g −1 ·h −1 , which was 2.4 times that of pristine CdS. The constructed heterojunction photocatalyst could supply H 2 O 2 in situ for nonspecific peroxygenases to catalyze the C-H oxyfunctionalization of ethylbenzene, achieving a yield of 81% and an ee value of 99% under optimum conditions. A wide range of substrates were converted to the corresponding chiral alcohols using this photo-enzyme catalytic system, achieving the corresponding chiral alcohols in good yield (51%–88%) and excellent enantioselectivity (90%–99% ee).
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