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To combat the energy crisis and environmental pollution, developing renewable energy technology such as hydrogen (H2) production is necessary. The sulfur–iodine thermochemical cycle has high commercial potential in conducting hydrogen iodide (HI) splitting for H2 generation, but it requires high‐temperature conditions. In comparison, photocatalytic HI splitting of halide perovskites is non‐polluted and low‐cost for H2 production at room temperature. Herein, an in situ constructed multidimensional bismuth (Bi)‐based 3D/2D EDABiI5/MA3Bi2I9 perovskite heterojunction is developed first by synergistically integrating dimensionality control with heterostructure engineering. Accordingly, the optimal EDABiI5/MA3Bi2I9 without any co‐catalysts exhibits the H2 evolution rate of 213.63 µmol h−1g−1 under irradiation. Equally importantly, interfacial dynamics of solid/solid and solid/liquid interfaces play a crucial role in photocatalytic performance. Therefore, using temperature‐dependent transient photoluminescence and electrochemical voltammetric techniques, it is confirmed that the exciton transportation of EDABiI5/MA3Bi2I9 is accelerated by stronger electronic coupling arising from an enhanced overlap of electronic wavefunctions. Moreover, the effective diffusion coefficient and electron transfer rate of EDABiI5/MA3Bi2I9 demonstrate efficient heterogeneous electron transfer, resulting in improved photocatalytic hydrogen production. Consequently, the in situ formation of perovskite heterostructures studied by a combination of photophysical and electrochemical techniques provides new insights into green hydrogen evolution and interfacial interaction dynamics for commercial applications of solar‐to‐fuel technology. [ABSTRACT FROM AUTHOR]

The over-use of fossil fuels leads to a sharp increase in atmospheric concentrations of carbon dioxide (CO2), which seriously contributes to the energy crisis and climate problems. The direct transformation of CO2 into high-value chemicals through photocatalysis offers an effective way to mitigate these problems. The key to achieving this goal is to discover a cost-effective, highly efficient, and durable photocatalyst. Due to their straightforward synthesis, high light absorption capacity, rapid exciton production efficiency, and long carrier diffusion length, nanoscale halide perovskites (NHPs) have great potential for solar photocatalysis. However, several crucial problems, like poor long-term stability, low product selectivity, and severe charge recombination, have become bottlenecks in the development of NHP photocatalysts. Therefore, this review aims to summarize the principles of the CO2 reduction reaction (CO2RR), the structural features of halide perovskites nanocrystals (NCs) in the system, and the principal approaches to enhancing their photocatalytic activity. Factors that influence the selectivity of CO2RR final products are also discussed. Moreover, this review pays special attention to the techniques for studying photogenerated carrier transport processes and photocatalytic intermediates, which make a significant contribution to the insight into the reaction mechanism of photocatalytic CO2 reduction. Finally, the main challenges and prospects for NHP's further development are also presented. This review will offer instructions for the design of NHP photocatalysts to further enhance the photocatalytic performance and product selectivity for CO2 reduction. It will also offer insights into studying the charge transport process and mechanism for the CO2 photocatalytic reduction reaction. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting is one of the promising approaches for generating hydrogen. Developing noble metal-free electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is important to achieve efficient water-splitting. This paper reviews the activity, stability, and durability of recently reported noble metal-free electrocatalysts such as oxides/hydroxides/(oxy)hydroxides/layered double hydroxides, sulfides, selenides, phosphides/phosphates, nitrides, carbon-based electrocatalysts, and alloy/B/V/F/Si based electrocatalysts for the HER and OER in an alkaline environment, including the strategies used to achieve high activity and stability/durability at a current density of ≥1000 mA cm−2. Moreover, this paper discusses the various promising strategies including the fabrication of nanostructured, ultrathin, porous, and nanoporous materials, preparing superaerophobic surfaces, construction of hollow structures, core–shell structures, heterostructures, heterojunctions, or Mott–Schottky heterojunctions, designing facile and/or scalable synthesis routes, creating doping and/or vacancies/defects, fabricating catalysts with high valence state sites, designing medium or high-entropy alloys, and tuning the atomic packing structure, electronic structure, or conductivity to enhance the activity and stability for the HER and/or OER. [ABSTRACT FROM AUTHOR]

Over the past few decades, organic–inorganic halide perovskites (OIHPs) as novel photocatalyst materials have attracted intensive attention for an impressive variety of photocatalytic applications due to their excellent photophysical (chemical) properties. Regarding practical application and future commercialization, the air–water stability and photocatalytic performance of OIHPs need to be further improved. Accordingly, studying modification strategies and interfacial interaction mechanisms is crucial. In this review, the current progress in the development and photocatalytic fundamentals of OIHPs is summarized. Furthermore, the structural modification strategies of OIHPs, including dimensionality control, heterojunction design, encapsulation techniques, and so on for the enhancement of charge‐carrier transfer and the enlargement of long‐term stability, are elucidated. Subsequently, the interfacial mechanisms and charge‐carrier dynamics of OIHPs during the photocatalytic process are systematically specified and classified via diverse photophysical and electrochemical characterization methods, such as time‐resolved photoluminescence measurements, ultrafast transient absorption spectroscopy, electrochemical impedance spectroscopy measurements, transient photocurrent densities, and so forth. Eventually, various photocatalytic applications of OIHPs, including hydrogen evolution, CO2 reduction, pollutant degradation, and photocatalytic conversion of organic matter. [ABSTRACT FROM AUTHOR]

Catalytically reducing CO2 offers an effective way to produce energy-rich fuels and high-value chemicals while simultaneously sequestrating CO2 from the environment. However, driving the CO2 reduction reaction (CO2RR) is challenging, because the linear molecular structure of CO2 is chemically inert with a low electron affinity. Thermal, light, and electrochemical energy are typically utilized to drive the CO2RR. One alternative route to reduce CO2 is via piezocatalysis. Piezocatalysis exploits the polarization of a material upon applying mechanical stress which enables spatial separation of the mechanically produced charge carriers to inhibit recombination. A piezocatalyst is uniquely suited to drive the CO2RR even in the dark without external heating and a sacrificial compound. Although the piezocatalytic CO2RR is just beginning to be explored, it is foreseen to become one of the most important scenarios for CO2 utilization. In this perspective, we discuss prospects and challenges of the piezocatalytic CO2RR. The received hypotheses on the piezocatalysis mechanism are critically discussed. Guidelines to obtain a potentially efficient piezocatalyst are outlined. We expect our contribution to inspire readers to get involved in this promising new area of research and bring it in the right direction. [ABSTRACT FROM AUTHOR]