Sunlight-driven photocatalysis has emerged as a potential technology to address organic pollutant issues. Here, we report the first Rh-doped hollow-structured TiO2 photocatalyst, which is highly active in the photocatalytic decomposition of organic pollutants under solar light. We achieved this by introducing Sr2+ as a co-doping agent, which stabilized the hollow structure at high temperatures and enabled us to control the oxidation state of Rh. The designed photocatalyst exhibited strong visible light absorption (up to 600 nm), and a very high surface area (up to 140 m2 g−1). As a result, the Sr/Rh-doped TiO2 hollow photocatalysts demonstrated a photocatalytic efficiency (PE) of 0.242%, which was at least 8 times higher than that of commercial TiO2 (0.03%) and 25 times higher than that of bulk Sr/Rh–TiO2 (0.01%), in the photocatalytic decomposition of isopropanol under solar light irradiation.
A critical drawback of existing materials, which restricts the photocatalytic efficiency, is the fast recombination of charge carriers. To address this challenge, loading reduction and oxidation co‐catalysts on two opposite surfaces of a hollow semiconductor is a critical approach to improve the photocatalytic performance. These co‐catalysts mainly act as oxidation and reduction active sites, while suppressing the charge recombination. Moreover, the development of a novel and efficient co‐catalyst that boosts charge separation is a very important feature for the photocatalytic performance. Herein, we report the first synthesis of hollow Pt/TiO2/CxNy‐triazine nanocomposite using carbon colloidal spheres as a hard template, in which Pt and CxNy‐triazine are located on the two opposite hollow surfaces. CxNy‐based triazine species formed from cyanamide during calcination do not only stabilize the hollow structure and significantly enhance the surface area of Pt/TiO2/CxNy‐triazine, but also act as an efficient oxidation co‐catalysts. This new type of nanocomposite exhibits one of the best TiO2‐based photocatalysts working under solar light irradiation to date. It is 125 and 62 times higher than that of Pt/TiO2–P25 for hydrogen generation and methanol decomposition, respectively.
3D architectures porous epsilon-type manganese dioxide (ε-MnO2) microcubes (PEMD) are successfully prepared by a glucose-urea-assisted hydrothermal synthesis of MnCO3-carbon composites followed by annealing. It turns out that urea essentially assists in building the cubic shape while glucose plays a crucial role to form carbon inside the microcrystals, which are latterly removed by annealing to generate the porous structure. As a result, ε-MnO2 materials possessing extraordinary features including the high porosity, reducibility, lattice oxygen reactivity and Mn4+ fraction, are feasible tailored. These unique properties, all together, significantly improve the catalytic performances of complete oxidation of toluene. Thus, it is found that the optimal catalyst (manganese-glucose-urea ratio of 6-2-6) synthesized at 180 °C exhibits an excellent activity for the complete oxidation of toluene (T90 = 243 °C, lower 10 °C than that of pristine ε-MnO2) and stability up to 10 h.
The photoassisted catalytic reaction, conventionally known as photocatalysis, is expanding into the field of energy and environmental applications. It is widely known that the discovery of TiO2‐assisted photochemical reactions has led to several unique applications, such as degradation of pollutants in water and air, hydrogen production through water splitting, fuel conversion, cancer treatment, antibacterial activity, self‐cleaning glasses, and concrete. These multifaceted applications of this phenomenon can be enriched and expanded further if this process is equipped with more tools and functions. The term “photoassisted” catalytic reactions clearly emphasizes that photons are required to activate the catalyst; this can be transcended even into the dark if electrons are stored in the material for the later use to continue the catalytic reactions in the absence of light. This can be achieved by equipping the photocatalyst with an electron‐storage material to overcome current limitations in photoassisted catalytic reactions. In this context, this article sheds lights on the materials and mechanisms of photocatalytic reactions under light and dark conditions. The manifestation of such systems could be an unparalleled technology in the near future that could influence all spheres of the catalytic sciences.
