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1. Visible-light-driven organic transformations integrated with H ₂ production on semiconductors

   https://doi.org/10.1039/D0MA00327A  

   Tang, Jian-Hong; Sun, Yujie (October 2020, Materials Advances)

   null (Ed.)

   Due to its clean and sustainable nature, solar energy has been widely recognized as a green energy source in driving a variety of reactions, ranging from small molecule activation and organic transformation to biomass valorization. Within this context, organic reactions coupled with H 2 evolution via semiconductor-based photocatalytic systems under visible light irradiation have gained increasing attention in recent years, which utilize both excited electrons and holes generated on semiconductors and produce two types of value-added products, organics and H 2 , simultaneously. Based on the nature of the organic reactions, in this review article we classify semiconductor-based photocatalytic organic transformations and H 2 evolution into three categories: (i) photocatalytic organic oxidation reactions coupled with H 2 production, including oxidative upgrading of alcohols and biomass-derived intermediate compounds; (ii) photocatalytic oxidative coupling reactions integrated with H 2 generation, such as C–C, C–N, and S–S coupling reactions; and (iii) photo-reforming reactions together with H 2 formation using organic plastics, pollutants, and biomass as the substrates. Representative heterogeneous photocatalytic systems will be highlighted. Specific emphasis will be placed on their synthesis, characterization, and photocatalytic mechanism, as well as the organic reaction scope and practical application. 

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2. Integrated design for electrocatalytic carbon dioxide reduction

   https://doi.org/10.1039/D0CY00453G  

   Zhao, Xin; Du, Lijie; You, Bo; Sun, Yujie (May 2020, Catalysis Science & Technology)

   null (Ed.)

   The electrocatalytic carbon dioxide reduction reaction (CO 2 RR) to produce valuable fuels and chemicals with renewable energy inputs is an attractive route to convert intermittent green energy sources ( e.g. , solar and wind) to chemical energy, alleviate our dependence on fossil fuels, and simultaneously reduce net carbon dioxide emission. However, the generation of reduced multi-carbon products with high energy density and wide applicability from the CO 2 RR, such as oxygenates and hydrocarbons, suffers from high overpotential, slow reaction rate, and low selectivity due to its intrinsic multi-electron transfer nature. Moreover, the involved anodic oxygen evolution reaction (OER) also requires large overpotential and its product O 2 bears limited economic value. The potentially generated reactive oxygen species (ROS) during the OER may also degrade the membrane of a CO 2 reduction electrolyzer. Herein, we review the recent progress in novel integrated strategies to address the aforementioned challenges in the electrocatalytic CO 2 RR. These innovative strategies include (1) concurrent CO 2 electroreduction via co-feeding additional chemicals besides CO 2 gas, (2) tandem CO 2 electroreduction utilizing other catalysts for converting the in situ formed products from the CO 2 RR into more valuable chemicals, and (3) hybrid CO 2 electroreduction through integrating thermodynamically more favourable organic upgrading reactions to replace the anodic OER. We specifically highlight these novel integrated electrolyzer designs instead of focusing on nanostructured engineering of various electrocatalysts, in the hope of inspiring others to approach CO 2 electroreduction from a holistic perspective. The current challenges and future opportunities of electrocatalytic CO 2 reduction will also be discussed at the end. 

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3. Photoelectrochemical water splitting under concentrated sunlight: best practices and protocols

   https://doi.org/10.3389/fenrg.2025.1550153  

   Li, Kejian; Dong, Wan Jae; Mi, Zetian (March 2025, Frontiers in Energy Research)

   Photoelectrochemical (PEC) water splitting is a promising technology for green hydrogen production by harnessing solar energy. Traditionally, this sustainable approach is studied under light intensity of 100 mW/cm²mimicking the natural solar irradiation at the Earth’s surface. Sunlight can be easily concentrated using simple optical systems like Fresnel lens to enhance charge carrier generation and hydrogen production in PEC water splitting. Despite the great potentials, this strategy has not been extensively studied and faces challenges related to the stability of photoelectrodes. To prompt the investigations and applications, this work outlines the best practices and protocols for conducting PEC solar water splitting under concentrated sunlight illumination, incorporating our recent advancements and providing some experimental guidelines. The key factors such as light source calibration, photoelectrode preparation, PEC cell configuration, and long-term stability test are discussed to ensure reproducible and high performance. Additionally, the challenges of the expected photothermal effect and the heat energy utilization strategy are discussed. 

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4. Minimizing Product Back Reactions with Inert Carrier Gas Bubbling for Photoelectrochemical Water Splitting with H ₂ /O ₂ Coevolution

   https://doi.org/10.1021/acs.energyfuels.4c04603  

   Mulvehill, Matthew C; Naveed, Abdul Basit; Spurgeon, Joshua M (February 2025, Energy & Fuels)

   Single-particle-type suspension reactors and other membrane-free reactor designs for photoelectrochemical (PEC) water splitting, although promising for low-cost H2 production, suffer the drawback of H2 and O2 co-evolution leading to product losses through back reactions. These back reactions need to be minimized to increase the solar-to-hydrogen (STH) efficiency. H2/O2 co-evolution also raises safety considerations, and a large-scale facility should maintain the H2 concentration below the lower flammability limit with O2 to eliminate explosion hazards. Herein, inert gas bubbling through the electrolyte was investigated with a tandem semiconductor for light-driven PEC water splitting without applied electrical bias as a technique to mitigate back reactions and maintain the output H2 safely below the lower flammability limit during co-evolution. A planar structure of nanoparticulate-Pt/Ni/np+-Si/FTO/TiO2 was fabricated into both wired-electrode and fully integrated configurations capable of unassisted solar water splitting, though additional UV bias increased the current density and gas production rates. The device was characterized in aqueous electrolyte from alkaline to neutral conditions to balance water-splitting activity and durability against corrosion, displaying strong stability in a pH 11 buffer solution. Moreover, the H2 faradaic efficiency was increased from 59% without bubbling to > 98% using inert carrier gas to increase the mass transfer of products to the gas phase. Integrated tandem photoelectrode performance indicated a tradeoff in bubbling flow rate between decreased back reactions and decreased light absorption due to bubble reflectance. 

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5. Molecular and Supramolecular Structures of Triiodides and Polyiodobismuthates of Phenylenediammonium and Its N,N-dimethyl Derivative

   https://doi.org/10.3390/molecules26185712  

   Shestimerova, Tatiana A.; Golubev, Nikita A.; Bykov, Mikhail A.; Mironov, Andrei V.; Fateev, Sergey A.; Tarasov, Alexey B.; Turkevych, Ivan; Wei, Zheng; Dikarev, Evgeny V.; Shevelkov, Andrei V. (September 2021, Molecules)

   Despite remarkable progress in photoconversion efficiency, the toxicity of lead-based hybrid perovskites remains an important issue hindering their applications in consumer optoelectronic devices, such as solar cells, LED displays, and photodetectors. For that reason, lead-free metal halide complexes have attracted great attention as alternative optoelectronic materials. In this work, we demonstrate that reactions of two aromatic diamines with iodine in hydroiodic acid produced phenylenediammonium (PDA) and N,N-dimethyl-phenylenediammonium (DMPDA) triiodides, PDA(I3)2⋅2H2O and DMPDA(I3)I, respectively. If the source of bismuth was added, they were converted into previously reported PDA(BiI4)2⋅I2 and new (DMPDA)2(BiI6)(I3)⋅2H2O, having band gaps of 1.45 and 1.7 eV, respectively, which are in the optimal range for efficient solar light absorbers. All four compounds presented organic–inorganic hybrids, whose supramolecular structures were based on a variety of intermolecular forces, including (N)H⋅⋅⋅I and (N)H⋅⋅⋅O hydrogen bonds as well as I⋅⋅⋅I secondary and weak interactions. Details of their molecular and supramolecular structures are discussed based on single-crystal X-ray diffraction data, thermal analysis, and Raman and optical spectroscopy. 

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