TiO 2 -based photocatalyst being inexpensive and abundant in conjunction with high photostability and environmental friendly characteristics makes it the most extensively studied photocatalytic material for hydrogen production and pollutant degradation. However, its existing issues such as wide bandgap, high overpotential and rapid recombination of photogenerated carriers limit its photocatalytic properties. The opportunities for structural development of TiO 2 nanomaterial towards highly efficient and pragmatic photocatalysis applications are evidently plentiful. Hence in this review, we will look into critical structural engineering strategies that endow favorable physicochemical properties such as improved light absorption, photostability, charge-carrier dynamics, increase surface area etc. that benefit photocatalysis functionalities. Amongst the various structural engineering constitutions, we will be covering the most prevalent and elegant core-shell and hierarchical structural designs that rationally combine the advantages of structural manipulation and multi-material composition engineering. This review aims to provide a comprehensive and contemporary overview as well as a guide of the development of new generation TiO 2 based photocatalysts via structural design for improved solar energy conversion technologies.
We have demonstrated an environmentally friendly and template-free aqueous synthesis of hierarchically assembled 3D ZnO nanoflakes. The ZnO nanoflakes self-assembled to expose highly interconnected networks of well-defined catalytic active {0001} facets. Well dispersed Pt, Ag and Au metal nanoparticles were loaded to form hybrid ZnO nanoflakes for enhanced photocatalytic activity. The enhanced photocatalytic activity may be attributed to the synergetic effects of well-structured ZnO crystal facets, high metal nanoparticles dispersity, enhanced light absorption and charge-transfer kinetics which leads to high photocatalytic degradation.
Capturing solar energy for thermal conversion in a highly efficient manner for steam‐electricity cogeneration is particularly opportune in the context of optimal solar energy utilization for concurrent water‐energy harvesting. Herein, an integrative photothermal evaporator/thermogalvanic cell with the desired optical, heat, water, and electrochemical management for synergistic steam‐electricity production is reported. Versatile layer by‐layer assembly is employed to integrate a hydrogel/metal‐oxide/polymer into a multilayer film with individually addressable thickness, composition, and structure. As such, the ultimate integrative multilayer film cell demonstrates a unified high surface area and conductive electrodes, broadband absorption, rapid water suction‐ion exchange, and thermal insulation properties. Thus, the designed cell immensely suppresses heat losses, achieving a high solar thermal conversion efficiency of 91.4% and maximum power outputs of ≈1.6 mW m−2. Additionally, the self‐floating, deformable, modular integral device presents appealing attributes such as salt‐rejection for viable seawater desalination, high mechanical stability, and resilience to demanding operating conditions, and configurable on‐demand/point‐of‐use tandem structure to maximize clean water and power generation value per area. This integrated strategy may provide prospective opportunities to reduce dependence on fossil fuels and freshwater inputs and solutions for renewable and decentralized clean water and electricity.
Utilizing solar energy for environmental and energy remediations based on photocatalytic hydrogen (H2) generation and water cleaning poses great challenges due to inadequate visible-light power conversion, high recombination rate, and intermittent availability of solar energy. Here, we report an energy-harvesting technology that utilizes multiple energy sources for development of sustainable operation of dual photocatalytic reactions. The fabricated hybrid cell combines energy harvesting from light and vibration to run a power-free photocatalytic process that exploits novel metal-semiconductor branched heterostructure (BHS) of its visible light absorption, high charge-separation efficiency, and piezoelectric properties to overcome the aforementioned challenges. The desirable characteristics of conductive flexible piezoelectrode in conjunction with pronounced light scattering of hierarchical structure originate intrinsically from the elaborate design yet facile synthesis of BHS. This self-powered photocatalysis system could potentially be used as H2 generator and water treatment system to produce clean energy and water resources.
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