Photocatalytic reduction of CO 2 is a promising strategy to alleviate the global energy crisis and environmental problems. Recently, metal halide perovskites with tunable bandgaps, large diffusion length, and abundant surface sites have drawn immense research interest for photocatalytic CO 2 reduction reactions. In this work, we develop an amorphous TiO 2 (aTiO 2 )encapsulated Cs 2 AgBiBr 6 double-perovskite nanocrystal (NC) by a room-temperature anti-solvent recrystallization method. Subsequently, we demonstrate the photocatalytic reduction of CO 2 to CH 4 (8.46 μmol g −1 h −1 ) and CO (5.72 μmol g −1 h −1 ) using this nanocomposite, where CH 4 is the dominant product. The Cs 2 AgBiBr 6 −aTiO 2 nanocomposite exhibits an 11-fold enhancement in the CH 4 yield compared to pristine Cs 2 AgBiBr 6 with prolonged stability of 16 h and higher selectivity of CH 4 over harmful CO production. The reason for the product selectivity is attributed to the presence of adventitious Ti 3+ on the surface of perovskite, which accelerates the CO 2 activation mechanism. The solvent effect on the product formation is also studied with ethyl acetate, acetonitrile, and dioxane. CH 4 becomes the dominant product in all of the cases, with an impressive evolution rate of 10.96 μmol g −1 h −1 in acetonitrile only. Impedance spectroscopy and ultrafast femtosecond transient absorption spectroscopy were used to establish the mechanism of CO 2 reduction. It was also confirmed that aTiO 2 helps in a faster and smoother charge transport at the interface by passivating the surface defects of the perovskite NCs. Our work provides a simple, highly efficient, and selective strategy for photocatalytic CO 2 reduction using doubleperovskite-based nanomaterial.

Organic photovoltaics have received active research interest during the past 30 years due to their low cost, flexibility, easy scalability, and robustness. Recently, several efforts have been made to enhance their power conversion efficiency (PCE) and stability by considering advanced photon harvesting technology, utilization of novel donor–acceptor materials, and optimizing device design strategy. Specifically, the photon multiplication process like singlet fission (SF) and design of novel materials, including low‐bandgap conjugated polymers and non‐fullerene acceptors (NFA), have led to the development of advanced organic photovoltaics with PCE close to theoretical Shockley–Queisser (SQ) limit. Here, an up‐to‐date overview of the recent progress during the last five years in advanced organic photovoltaics with a special focus on emerging techniques and materials was reported. Further, various designing and deployment strategies for these processes and materials were explored along with their properties, challenges, and achievements. Finally, a strategy for the next‐stage research directions was analyzed and proposed that could drive this field even further beyond laboratory research to reach the final goal of commercialization.

photocatalyst materials for its low cost, non-toxicity, and improved photochemical stability. But its large bandgap acts as a limiting factor for fruitful utilization of solar photons. Like TiO 2 , [1] the ABO 3 and AB 2 O 4 structure materials are large bandgap semiconductors that only act in the UV region. [2] Meanwhile, the family of other oxides materials such as ABO 4 , ABO 2 , Aurivillius oxides, and ternary chalcogenides is visible light absorptive materials. Still, their unsuitable band edge alignments make them inappropriate to catalyze important reactions, inherently limiting their use. [3] Therefore, the unsatisfactory photoreduction potential of these materials due to their large bandgap and rapid charge carrier recombination properties fuel an intense desire to design new semiconductor-based photocatalyst systems [4][5][6][7] with appropriate photo properties through novel materials exploration.Recently, metal halide perovskites (MHPs) have become star performers in the global research platform. Their prominence started with the research mainly emphasizing photovoltaics and LEDs' applications and fundamental properties' investigations. Convinced with the versatile and unique properties of MHPs, their application has been extended in other novel and advanced technologies such as optical sensing, [8] X-ray detection, [9] lasing, [10] flash memory, [11] and various photocatalytic processes including organic contaminant degradation, [12][13][14][15][16][17][18][19][20][21][22][23][24] CO 2 reduction, [25][26][27][28][29][30][31][32][33][34][35][36][37] organic reactions, [38][39][40][41] etc. Particularly, MHP nanocrystals in photoredox organic synthesis such as CC, CO, and CN bond formations have been proved to be revolutionary in fundamental applications of material synthesis and drug development. [42][43][44] MHPs have beneficial features such as low-cost production, tunable bandgap, long diffusion lengths, high charge carrier mobility, easy solution synthesis methods, a desired charge transfer for redox reactions, and unusual defects tolerance, rendering them a potential candidate for photocatalytic applications. [45] The antibonding B-site (p) orbitals in the valence band and hybridized X (p)−B (s) orbital in conduction band offers optically tunable properties in MHP that provide MHPs the upper hand over conventional semiconductor photocatalysts. [46] However, bare semiconductor photocatalytic systems face major limitations, which hinder their applicability. One of the challenges is poor compatibility between the light response range and strong redox ability. The bandgap requirement Photocatalytic hydrogen generation paves a promising way to mitigate the global energy crisis and deteriorative environmental issues. Among different materials, metal halide perovskites (MHPs) have recently emerged as a promising class of inexpensive and easy-to-make semiconductors for various photocatalytic applications such as organic contaminant degradation, CO 2 reduction, H 2 evolution, and N 2 fixation. Although...

Oxide perovskite materials with ABO3 structure have been widely employed for photocatalytic applications. However, owing to the disadvantageous electron–hole recombination process and wide bandgap of some materials, the photocatalytic performance is seemingly restricted. Coupling two catalysts together through the formation of a heterojunction ensures effective charge carrier separation. The intimate interaction between the materials is propitiously useful for charge transfer, thereby increasing the efficacy. In this study, the photocatalytic activity of a K x Na(1‑x)NbO3–BaBiO3 (KNN-BBO) heterojunction material for the degradation of Rhodamine 6G organic dye was investigated. The materials were extensively characterized by X-ray diffraction, UV–Vis diffused reflectance spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and N2 adsorption isotherms. The degradation efficiency of the organic contaminant under 1 sun simulated sunlight is monitored by spectral analysis from UV–Vis absorption spectroscopy. The resistance to charge transfer was also observed by electrochemical impedance spectroscopy. The effect of the sintering temperature on the photoinduced degradation activity was also included in our study. An unsintered KNN-BBO (UKB) composite material is found to be the most efficient catalyst with 84% removal efficiency as compared to the sintered one (SKB). This is attributed to the reduced bandgap with staggered-type band alignment, increased surface area, and surface oxygen vacancy states. Together with the crucial findings of this work, a probable mechanism for enhanced photocatalytic activity has been proposed here.

Arsenic (As) contamination in drinking water is a global concern. Development of facile and low cost As remediation system is of significant social and economic interest. Here, we report a cost-effective and water-stable transition metal oxide doped cross-linked chitosan cryogel for highly sensitive removal of As ion from potable water. Sample aliquots were tested for total arsenic by inductively coupled plasma mass spectroscopy. It was found that the sorption kinetics follows Freundlich isotherm model. We observe remarkably high arsenic removal efficiency (76%) with only 2 h of contact time with cryogel. The scaffold materials can be easily regenerated with acetone. The high removal efficiency of As metal and recyclability of this novel synthesized metal oxide doped cross linked chitosan cryogel render them a potential candidate for low cost arsenic removal based filter development.