Surface plasmon resonance enhancement of production of H2 from ammonia borane solution with tunable Cu2−xS nanowires decorated by Pd nanoparticles

Localized surface plasmon resonances (LSPR) in near-infrared (NIR) region have been extensively studied for copper chalcogenide nanostructures, not only for the absorption enhancement but also tunable LSPR characteristics with their free carrier concentrations or defects. In the present work, one-step cation exchange method has been used to synthesize Cu2−xS nanowires with x varied between 0 and 1, including Cu2S, Cu7S4 and CuS and so forth. The plasmonic band of Cu2−xS nanowires shifts to a shorter wavelength with the increase in x, as observed in vis-NIR spectra, which is attributed to the increase in density of copper vacancies. The Cu2−xS nanowires have been used as catalysts towards the photocatalytic generation of H2 from ammonia borane (AB). Among samples with different Cu-S compositions, Cu7S4 samples exhibited the highest activity in terms of H2 evolution rate (25.54 mmol/g h). Moreover, a marked enhancement of the H2 evolution rate (157.04 mmol/g h) could be achieved after decorating the Cu2−xS nanowires with Pd nanoparticles to form the hybrid structures. The results of the present investigation may lead to an effective strategy for the design and development of LSPR materials for photocatalytic applications

Unveiling the effect of sacrificial agent amount in the CO2 photoreduction performed in a flow reactor

The use of sacrificial agents in photocatalysis is a powerful resource to enhance the performance of photoactive materials. Despite its importance, the effect of the amount of sacrificial agent is not properly described in the literature. In this paper, we have focused on the role of EtOH in the photoreduction of CO2 to CH4 using Cu-P25 photocatalysts in a flow reactor. We found that the production of CH4 increased with the concentration of EtOH, achieving an outstanding CH4 production yield of 235 µmol/(g·h) for a flow of 0.25 µmol/min of EtOH in the gas stream, hinting at the important role of the sacrificial agent in the reaction. The catalytic results together with the characterization of the materials highlight the need to achieve a minimum surface coverage of EtOH on the surface of the catalyst to control the reaction pathway. The adsorption of EtOH is a key factor in boosting the catalytic activity of the best-performing catalyst and producing CH4 from CO2 photoreduction and C2H4O from the photooxidation of EtOH, obtaining two easily separable interesting products for industrial applications in one reaction

Preparation of a ruthenium complex covalently bonded to multilayer graphene and its evaluation as a photocatalyst

Multilayer graphene (MLG), obtained by mild sonication of graphite in NMP, was functionalised via 1,3-dipolar cycloaddition with azomethine ylides generated by thermal 1,2-prototropy from various imino esters. The microwave-assisted functionalisation took place in five hours at 100 °C. The resulting MLG, containing substituted proline-based amine functional groups, was characterized using XPS and showed a nitrogen loading three times that obtained for the same transformation performed for five days using convection-assisted heating. The preparation of the imino ester containing a bipyridine unit at the arylidene position allowed for the preparation of the corresponding functionalised MLG, which incorporated the ruthenium atom to achieve a heterogeneous MLG-Ru complex. This supported complex was tested, as a proof of concept, as a photocatalyst of the aerobic oxidative hydroxylation of 4-methoxyphenylboronic acid.We gratefully acknowledge financial support from the Spanish Ministerio de Ciencia, Innovación y Universidades (project RED2018-102387-T), the Spanish Ministerio de Economía, Industria y Competitividad, Agencia Estatal de Investigación (AEI) and Fondo Europeo de Desarrollo Regional (FEDER, EU) (projects CTQ2017-82935-P and PID2019-107268GB-I00), the Generalitat Valenciana (IDIFEDER/2021/013, GVA-COVID19/2021/079 and CIDEGENT/2020/058), Medalchemy S. L. (Medalchemy-22T) and the University of Alicante (VIGROB-068, UAUSTI21-05). LVR-F thanks Generalitat Valenciana for Grisolía's fellowship (GRISOLIAP/2020/111). This work is also part of the R+D+I project PID2021-123079OB-I00 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”. MNG is grateful for the grant RYC2021-034199-I funded by MCIN/AEI/10.13039/501100011033 and by “ESF Investing in your future”

g-C₃N₄-based direct Z-Scheme photocatalysts for environmental applications

Abstract Photocatalysis represents a promising technology that might alleviate the current environmental crisis. One of the most representative photocatalysts is graphitic carbon nitride (g-C₃N₄) due to its stability, cost-effectiveness, facile synthesis procedure, and absorption properties in visible light. Nevertheless, pristine g-C₃N₄ still exhibits low photoactivity due to the rapid recombination of photo-induced electron-hole (e⁻-h⁺) pairs. To solve this drawback, Z-scheme photocatalysts based on g-C₃N₄ are superior alternatives since these systems present the same band configuration but follow a different charge carrier recombination mechanism. To contextualize the topic, the main drawbacks of using g-C₃N₄ as a photocatalyst in environmental applications are mentioned in this review. Then, the basic concepts of the Z-scheme and the synthesis and characterization of the Z-scheme based on g-C₃N₄ are addressed to obtain novel systems with suitable photocatalytic activity in environmental applications (pollutant abatement, H₂ production, and CO₂ reduction). Focusing on the applications of the Z-scheme based on g-C₃N₄, the most representative examples of these systems are referred to, analyzed, and commented on in the main text. To conclude this review, an outlook of the future challenges and prospects of g-C₃N₄-based Z-scheme photocatalysts is addressed