Elucidating the Origin of Enhanced Photocatalytic Hydrogen Production on Tuned Cu7S4/CdS Heterostructures

Direct Z-scheme Cu 7 S 4 /CdS Janus photocatalysts are successfully prepared by cation exchange method. Extensive studies containing single-nanoparticle impact electrochemistry are performed and reveal that optimizing the Cu 7 S 4 /CdS ratio can decrease the accumulation of holes on valence band of CdS for inhibiting photocorrosion and promote the accumulation of electrons on the conduction band of Cu 7 S 4 for boosting the electron reducibility. With the optimized heterostructures, hydrogen evolution is remarkable promoted up to 21.62 mmol h -1 and quantum efficiency is up to 14.37 % using polylactic acid plastic waste as feedstock.

Supercritically exfoliated Bi2Se3 nanosheets for enhanced photocatalytic hydrogen production by topological surface states over TiO2

Owing to the unique electronic properties of layered materials, topological insulators have interestingly grabbed much attention in the field of photocatalytic water splitting. Nowadays, 2D layered materials were composited with semiconductor photocatalysts, encourage much as it provides enormous active sites and also significantly prevent photogenerated charge recombination. Especially, Bi₂Se₃ possesses exceptional properties like topologically preserved conducting surface states with bulk insulating behavior and high surface area, which provides unconventional electron dynamics, resulting in facile electron transport and effective charge separation to photocatalyst. So far, several methods have been attempted to synthesize few-layered Bi₂Se₃ nanosheets from its bulk crystals. Here, a unique attempt is made and succeeded to exfoliate bulk Bi₂Se₃ to few layered nanosheets via surfactant free supercritical fluid processing using N-Methyl-2-pyrrolidone (NMP) as an exfoliating agent, with a short reaction time of 15 min. The exfoliation of Bi₂Se₃ crystal was confirmed by several characterization techniques, such as XRD, SEM, Raman, and HR-TEM. Furthermore, different weight percentages of exfoliated Bi₂Se₃ sheets/anatase TiO₂ nanoparticles were prepared and examined the photocatalytic activity using glycerol as a hole scavenger. Among them, 15 wt.% Bi₂Se₃ coupled TiO₂ nanocomposite showed enormous hydrogen evolution rate of 84.9 mmol h^-1g^-1_cat, which is 80 times higher than that of TiO₂ nanoparticles. In addition, the photostability of the nanocomposite was also verified, where it retains 94% of activity even after 4 cycles of continuous experiments. The improved rate of H₂ production was understood by theoretical calculations that topologically preserved conducting surface states of co-catalyst, Bi₂Se₃ nanosheets is supported to high mobile and scatter free electrons. It mediates the transport of electrons with TiO₂ nanoparticles that helped the effective charge separation. Thus, it proves a promising candidate for photocatalytic hydrogen production.

Designing novel morphologies of l-cysteine surface capped 2D covellite (CuS) nanoplates to study the effect of CuS morphologies on dye degradation rate under visible light

Novel CuS@l-Cys NPs are designed by a hydrothermal route. The effects of synthetic parameters on the morphologies of CuS@l-Cys NPs were investigated. CuS@l-Cys NPs exhibit an enhanced dye degradation rate under visible light.