This work studies the effect of the temperature in the solvothermal synthesis of CdS modified with Ag (Ag-CdS) over both the structure of CdS and the chemical state of the Ag species. The increase in the solvothermal temperature produces the evolution of the CdS nanostructures from nanoparticles of low crystallinity in coexistence with small nanocrystals with strong confinement effect to the formation of highly crystalline nanorods. The Ag species also change with the solvothermal temperature from Ag₂S species, formed at low temperature, to metallic species as the temperature increases. The photoactivity of the Ag-CdS samples is the result of the combination of three factors: crystallinity of the CdS structures, existence of small nanocrystals with strong confinement effect and the presence of segregated Ag₂S species. The Ag-CdS sample prepared at 120 °C shows the better efficiency for hydrogen production because it achieves the better combination of the aforementioned factors., The present work was performed within the research program supported by under the project and CAM within the S2013/MAE-288 project. This research was funded by MINECO (Spain), grant number CTQ2016-76505-C3-1-R. E. Soto would like to acknowledge MINECO for the FPI research grant., We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI), Peer reviewed

© 2020 by the authors., The aim of this work is to study the influence of the sulphur source (elemental sulphur, thiourea and L-cysteine) in the solvothermal synthesis of Ag-CdS over its growth, structuration and state of Ag and how these changes influence on its photoactivity. The differences in the generation rate of the S2− from the sulphur sources during the solvothermal synthesis determine the nucleation and growth pathways of CdS affecting to the silver state and its incorporation into the CdS lattice. The hydrogen production on Ag-CdS photocatalysts decreases according the sequence: thiourea > elemental sulphur >> L-cysteine. The changes in the photoactivity of Ag-CdS samples are analysed in terms of the differences in the insertion of Ag+ into the CdS lattice, the formation of composites between CdS and Ag2S and the formation of CdS crystalline domains with strong confinement effect derived from the different sulphur source used in the solvothermal synthesis., The present work was performed within the research program supported by MINECO (Spain) under the projects CTQ2016-76505-C3-1-R and PID2019-1112119RB-100 and CAM within the BIOTRES-CM (S2018/EMT-4344) project. E. Soto would like to acknowledge MINECO for the FPI research grant., Peer reviewed

This work is dedicated to the study of the effect of the synthesis conditions (drying and calcination) of sulfated zirconia on the final catalytic behavior of bifunctional composite catalysts prepared by the physical mixing of the sulfated zirconia (methanol dehydration catalyst) with Cu/ZnO/Al2O3 (CZA; methanol synthesis catalyst). The main objective was to optimize the CZA-ZrO2/SO42− composite catalyst for its use in the direct production of dimethyl ether (DME) from syngas. Sulfated zirconia aerogel (AZS) and xerogel (XZS) were prepared using the sol–gel method using different solvent evacuation conditions and calcination temperatures, while the Cu-ZnO(Al) catalyst was synthesized using the coprecipitation procedure. The effectivity of CZA-ZrO2/SO42− composite catalysts for the direct production of dimethyl ether (DME) from syngas was evaluated in a flow reactor at 250 °C and 30 bar total pressure. The characterization of the sulfated zirconia aerogels and xerogels using different techniques showed that the mesoporous aerogel (AZS0.5300) exhibited the best textural and acidic properties due to the gel drying under supercritical conditions and calcination at 300 °C. As a result, the composite catalyst CZA-AZS0.5300 exhibited seven times higher DME production than its xerogel-containing counterpart (364 vs. 52 μmolDME·min−1·gcat−1). This was attributed to its well-matched metal surface, mesoporous structure, optimal crystallite size and, most importantly, its higher acidity., he authors gratefully acknowledge the financial support provided by the Tunisian Ministry of Higher Education and Scientific Research and by the research programs PID2019–111219RB-100 and PID 2022-143180OB-I00 supported by the Spanish Ministry of Science, Innovation and Universities. E.M.O. and C.Q.R. would like to acknowledge the FPI programme of the Spanish Ministry of Science, Innovation and Universities for their research grants (PRE2020-094027 and BES-2017-080240)., Peer reviewed