Morphology-Governed Performance of Multi-Dimensional Photocatalysts for Hydrogen Generation

Modulation of the Structure of the Conjugated Polymer TMP and the Effect of Its Structure on the Catalytic Performance of TMP-TiO2 under Visible Light: Catalyst Preparation, Performance and Mechanism

The photocatalytic activity of titanium dioxide (TiO₂) is largely hindered by its low photoresponse and quantum efficiency. TiO₂ modified by conjugated polymers (CPs) is considered a promising approach to enhance the visible light responsiveness of TiO₂. In this work, in order to investigate the effect of CP structural changes on the photocatalytic performance of TiO₂ under visible light, trimesoyl chloride-melamine polymers (TMPs) with different structural characteristics were created by varying the parameters of the polymerisation process of tricarbonyl chloride (TMC) and melamine (M). The TMPs were subsequently composited with TiO₂ to form complex materials (TMP-TiO₂) using an in situ hydrothermal technique. The photocatalytic activity of TMP-TiO₂ was evaluated by the degradation of rhodamine B (RhB). The results showed that the trend of the structure of the TMP with the reaction conditions was consistent with the visible light responsiveness of TMP-TiO₂, and TMP (1:1)-TiO₂ had the best photocatalytic activity and could degrade 96.1% of the RhB. In conclusion, our study provided new insights into the influence of the structural changes of TMPs on the photocatalytic activity of TMP-TiO₂ under visible light, and it improves our understanding of how conjugated polymers affect the photocatalytic activity of TiO₂ under visible light.

Nanoengineering of Catalysts for Enhanced Hydrogen Production

Hydrogen (H2) has emerged as a sustainable energy carrier capable of replacing/complementing the global carbon-based energy matrix. Although studies in this area have often focused on the fundamental understanding of catalytic processes and the demonstration of their activities towards different strategies, much effort is still needed to develop high-performance technologies and advanced materials to accomplish widespread utilization. The main goal of this review is to discuss the recent contributions in the H2 production field by employing nanomaterials with well-defined and controllable physicochemical features. Nanoengineering approaches at the sub-nano or atomic scale are especially interesting, as they allow us to unravel how activity varies as a function of these parameters (shape, size, composition, structure, electronic, and support interaction) and obtain insights into structure–performance relationships in the field of H2 production, allowing not only the optimization of performances but also enabling the rational design of nanocatalysts with desired activities and selectivity for H2 production. Herein, we start with a brief description of preparing such materials, emphasizing the importance of accomplishing the physicochemical control of nanostructures. The review finally culminates in the leading technologies for H2 production, identifying the promising applications of controlled nanomaterials.

Enhanced Photocatalytic Activity of Hierarchical Bi2WO6 Microballs by Modification with Noble Metals

Visible-responsive photocatalysts for environmental purification and fuel generation are, currently, highly sought after. Among the possible candidates, Bi2WO6 (BWO) has been considered due to its efficient light harvesting, stability, and promising activities. Here, hierarchical BWO microballs have been prepared using a hydrothermal method, and additionally modified with deposits of noble metals (gold, silver, copper, palladium and platinum) by the photodeposition method. The structure, morphology, photoabsorption properties, and surface composition of bare and metal-modified BWO samples were investigated by XRD, SEM, DRS and XPS analyses. The photocatalytic activity was evaluated by the oxidative degradation of model dye (methyl orange (MO)) under UV/vis, and hydrogen generation under vis and/or UV irradiation. It was found that hierarchical morphology is detrimental for high photocatalytic activity in both tested systems, resulting in the improved degradation of MO (ca. 65% during 90 min of UV/vis irradiation), and hydrogen evolution (0.1 and 0.4 μmol h−1 under vis and UV/vis irradiation, respectively). Moreover, the type of noble metal and its properties influence the overall photocatalytic performance. It was found that, under UV/vis irradiation, only platinum accelerates hydrogen evolution, whereas under vis irradiation the activity follows the order: BWO < BWO/Cu < BWO/Ag < BWO/Pt < BWO/Pd < BWO/Au. It was concluded that zero-valent metal is recommended for high vis response, probably due to plasmonic photocatalysis, efficient light harvesting ability, and co-catalytic role.