The use of solar energy to catalyze the photo-driven processes has attracted tremendous attention from the scientific community because of its great potential to address energy and environmental issues. In this regard, several attempts have been made by researchers to design and develop different materials with enhanced photocatalytic efficiencies. This Review comprehensively summarizes the recent reports on perovskite oxide based photocatalysts for organic pollutant degradation, water splitting, carbon dioxide conversion, and nitrogen fixation along with the basic understanding of involved mechanisms, current trends and advances in the field. The different design, synthesis, and development strategies have been discussed in detail to provide a comprehensive view of materials’ fabrication that influences their photocatalytic properties. Subsequently, the insights from recent reports on different perovskite oxide based materials, including simple oxides, mixed oxides, and layered perovskite oxides, are provided for the above-mentioned photocatalytic applications in a detailed manner. Finally, a summary of photocatalytic applications and a perspective on future research direction have been discussed. Based on the research progress in this field, it is highly anticipated that the photocatalytic systems, comprising perovskite oxide materials along with groundbreaking technologies for large-scale realization of these processes, can be established in the near future to address the energy and environment-oriented challenges.

Scheme 1. Different strategies and concepts employed in the design and development of photocatalysts based on a semiconductor, such as TiO 2 , and plasmonic NPs.

It is a well‐known fact that the pronounced photogenerated charge recombination and poor light absorption are the main bottlenecks of photocatalysis applications. The conventional approaches to address these problems involve bandgap engineering and suppression of charge recombination after light irradiation, which results in an enhancement in the photocatalytic performance of the materials. However, the most essential aspect of surface modification to engineer active sites on the catalyst surface is generally not given much importance. Contrary to this, defect engineering is another approach by which the optical, charge separation, and surface properties of the photocatalytic materials can be tuned. In this review article, the effect of the introduction of vacancies on the photocatalytic properties of selected semiconductor materials, viz., metal oxides, perovskite oxides, metal sulfides, oxyhalides, and nitrides is comprehensively summarized. The engineering of vacancies in these materials not only improves their optical and charge transfer properties but also affects the surface properties, which are helpful in the adsorption of the reactants on catalyst surface. Herein, photocatalytic hydrogen evolution and nitrogen fixation applications of vacancy engineered materials are discussed in detail along with the current trends, scalability requirements, and rigorous experimental protocols.

The development of noble metal-free catalysts for hydrogen evolution is required for energy applications. In this regard, ternary heterojunction nanocomposites consisting of ZnO nanoparticles anchored on MoS -RGO (RGO=reduced graphene oxide) nanosheets as heterogeneous catalysts show highly efficient photocatalytic H evolution. In the photocatalytic process, the catalyst dispersed in an electrolytic solution (S and SO ions) exhibits an enhanced rate of H evolution, and optimization experiments reveal that ZnO with 4.0 wt % of MoS -RGO nanosheets gives the highest photocatalytic H production of 28.616 mmol h g under sunlight irradiation; approximately 56 times higher than that on bare ZnO and several times higher than those of other ternary photocatalysts. The superior catalytic activity can be attributed to the in situ generation of ZnS, which leads to improved interfacial charge transfer to the MoS cocatalyst and RGO, which has plenty of active sites available for photocatalytic reactions. Recycling experiments also proved the stability of the optimized photocatalyst. In addition, the ternary nanocomposite displayed multifunctional properties for hydrogen evolution activity under electrocatalytic and photoelectrocatalytic conditions owing to the high electrode-electrolyte contact area. Thus, the present work provides very useful insights for the development of inexpensive, multifunctional catalysts without noble metal loading to achieve a high rate of H generation.

Electrochemical-coupling layer-by-layer (ECC-LbL) assembly is introduced as a novel fabrication methodology for preparing layered thin films. This method allows us to covalently immobilize functional units (e.g., porphyrin, fullerene, and fluorene) into thin films having desired thicknesses and designable sequences for both homo- and heteroassemblies while ensuring efficient layer-to-layer electronic interactions. Films were prepared using a conventional electrochemical setup by a simple and inexpensive process from which various layering sequences can be obtained, and the photovoltaic functions of a prototype p/n heterojunction device were demonstrated.

A versatile method for the rapid fabrication of aligned fullerene C60 nanowhiskers (C60NWs) at the air-water interface is presented. This method is based on the vortex motion of a subphase (water), which directs floating C60NWs to align on the water surface according to the direction of rotational flow. Aligned C60NWs could be transferred onto many different flat substrates, and, in this case, aligned C60NWs on glass substrates were employed as a scaffold for cell culture. Bone forming human osteoblast MG63 cells adhered well to the C60NWs, and their growth was found to be oriented with the axis of the aligned C60NWs. Cells grown on aligned C60NWs were more highly oriented with the axis of alignment than when grown on randomly oriented nanowhiskers. A study of cell proliferation on the C60NWs revealed their low toxicity, indicating their potential for use in biomedical applications.

Sulfonated graphitic carbon nitride having both Brønsted base and Brønsted acid sites is used as a heterogeneous catalyst for the selective conversion of different biomass-derived saccharides to 5-hydroxymethylfurfural in green solvents.

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