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1. Ultrathin‐Film Titania Photocatalyst on Nanocavity for CO 2 Reduction with Boosted Catalytic Efficiencies

   https://doi.org/10.1002/gch2.201800032  

   Song, Haomin ; Wu, Wei ; Liang, Jian‐Wei ; Maity, Partha ; Shu, Yuying ; Wang, Nam Sun ; Mohammed, Omar F. ; Ooi, Boon S. ; Gan, Qiaoqiang ; Liu, Dongxia ( September 2018 , Global Challenges)

   Photocatalytic CO₂reduction with water to hydrocarbons represents a viable and sustainable process toward greenhouse gas reduction and fuel/chemical production. Development of more efficient catalysts is the key to mitigate the limits in photocatalytic processes. Here, a novel ultrathin‐film photocatalytic light absorber (UFPLA) with TiO₂films to design efficient photocatalytic CO₂conversion processes is created. The UFPLA structure conquers the intrinsic trade‐off between optical absorption and charge carrier extraction efficiency, that is, a solar absorber should be thick enough to absorb majority of the light allowable by its bandgap but thin enough to allow charge carrier extraction for reactions. The as‐obtained structures significantly improve TiO₂photocatalytic activity and selectivity to oxygenated hydrocarbons than the benchmark photocatalyst (Aeroxide P25). Remarkably, UFPLAs with 2‐nm‐thick TiO₂films result in hydrocarbon formation rates of 0.967 mmol g⁻¹h⁻¹, corresponding to 1145 times higher activity than Aeroxide P25. This observation is confirmed by femtosecond transient absorption spectroscopic experiments where longer charge carrier lifetimes are recorded for the thinner films. The current work demonstrates a powerful strategy to control light absorption and catalysis in CO₂conversion and, therefore, creates new and transformative ways of converting solar energy and greenhouse gas to alcohol fuels/chemicals.

    

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2. Electro- and Photocatalytic Conversion of N 2 to NH 3 by Chemically Modified Transition Metal Dichalcogenides, MoS 2 , and WS 2

   https://doi.org/10.1149/1945-7111/acd02d  

   Ganesan, Ashwin ; Alhowity, Samar ; Alsaleh, Ajyal Z. ; Guragain, Manan ; Omolere, Olatomide ; Cundari, Thomas R. ; Kelber, Jeffry ; D’Souza, Francis ( May 2023 , Journal of The Electrochemical Society)

   Electro- and photocatalytic reduction of N 2 to NH 3 —the nitrogen reduction reaction (NRR)—is an environmentally- and energy-friendly alternative to the Haber-Bosch process for ammonia production. There is a great demand for the development of novel semiconductor-based electrocatalysts with high efficiency and stability for the direct conversion of inert substrates—including N 2 to ammonia—using visible light irradiation under ambient conditions. Herein we report electro-, and photocatalytic NRR with transition metal dichalcogenides (TMDCs), viz MoS 2 and WS 2 . Improved acid treatment of bulk TMDCs yields exfoliated TMDCs (exTMDCs) only a few layers thick with ∼10% S vacancies. Linear scan voltammograms on exMoS 2 and exWS 2 electrodes reveal significant NRR activity for exTMDC-modified electrodes, which is greatly enhanced by visible light illumination. Spectral measurements confirm ammonia as the main reaction product of electrocatalytic and photocatalytic NRR, and the absence of hydrazine byproduct. Femtosecond-resolved transient absorption studies provide direct evidence of interaction between photo-generated excitons/trions with N 2 adsorbed at S vacancies. DFT calculations corroborate N 2 binding to exMoS 2 at S-vacancies, with substantial π -backbonding to activate dinitrogen. Our findings suggest that chemically functionalized exTMDC materials could fulfill the need for highly-desired, inexpensive catalysts for the sustainable production of NH 3 using Sunlight under neutral pH conditions without appreciable competing production of H 2 . 

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3. Metal‐Organic Framework Derived Terephthalate Ligand Decorated TiO 2 with Various Morphologies for Efficient Photocatalytic H 2 Evolution

   https://doi.org/10.1002/chem.202203917  

   Dong, Pengyu ; Gao, Kangjie ; Li, Kang ; Wang, Haoyu ; Xi, Xinguo ; Feng, Pingyun ( March 2023 , Chemistry – A European Journal)

   It has been rarely reported the morphological control of derivatives of metal‐organic frameworks (MOFs) in hydrothermal conditions for photocatalytic applications. We report here a family of highly efficient composite photocatalysts composed of terephthalic acid/terephthalate (TPA) ligand and TiO₂with various morphologies (e. g., nanoparticles, nanosheets, and nanorods). The composites are synthesized by a simple one‐step hydrothermal method in various solvents (i. e., H₂O, HF, H₂SO₄, HCl, and HNO₃) using Ti‐based MOF (MIL‐125(Ti)) as precursor. The formation mechanism of composite materials with different morphological features is discussed. Impressively, the composite of TiO₂nanoparticles/TPA synthesized using H₂O as solvent under hydrothermal condition exhibits the highest photocatalytic H₂activity among the studied materials, with a photocatalytic H₂production rate of 6.38 mmol g⁻¹ h⁻¹, which is approximately 7.5‐fold higher than pure TiO₂(Degussa, P25) and prominent apparent quantum efficiency (AQE) of 65 % at 365 nm. Furthermore, the mechanism of boosted photocatalytic H₂production is discussed.

    

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4. Screening and Discovery of Metal Compound Active Sites for Strong and Selective Adsorption of N 2 in Air

   https://doi.org/10.1002/cssc.202300948  

   Tian, Nianhan ; Comer, Benjamin M. ; Medford, Andrew J. ( November 2023 , ChemSusChem)

   Photocatalytic nitrogen fixation has the potential to provide a greener route for producing nitrogen‐based fertilizers under ambient conditions. Computational screening is a promising route to discover new materials for the nitrogen fixation process, but requires identifying “descriptors” that can be efficiently computed. In this work, we argue that selectivity toward the adsorption of molecular nitrogen and oxygen can act as a key descriptor. A catalyst that can selectively adsorb nitrogen and resist poisoning of oxygen and other molecules present in air has the potential to facilitate the nitrogen fixation process under ambient conditions. We provide a framework for active site screening based on multifidelity density functional theory (DFT) calculations for a range of metal oxides, oxyborides, and oxyphosphides. The screening methodology consists of initial low‐fidelity fixed geometry calculations and a second screening in which more expensive geometry optimizations were performed. The approach identifies promising active sites on several TiO₂polymorph surfaces and a VBO₄surface, and the full nitrogen reduction pathway is studied with the BEEF‐vdW and HSE06 functionals on two active sites. The findings suggest that metastable TiO₂polymorphs may play a role in photocatalytic nitrogen fixation, and that VBO₄may be an interesting material for further studies.

    

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5. Ni 2 P‐Modified Ta 3 N 5 and TaON for Photocatalytic Nitrate Reduction

   https://doi.org/10.1002/cnma.202000174  

   Wei, Lin ; Adamson, Marquix A. S. ; Vela, Javier ( May 2020 , ChemNanoMat)

   Self‐sustaining photocatalytic NO₃⁻reduction systems could become ideal NO₃⁻removal methods. Developing an efficient, highly active photocatalyst is the key to the photocatalytic reduction of NO₃⁻. In this work, we present the synthesis of Ni₂P‐modified Ta₃N₅(Ni₂P/Ta₃N₅), TaON (Ni₂P/TaON), and TiO₂(Ni₂P/TiO₂). Starting with a 2 mM (28 g/mL NO₃⁻−N) aqueous solution of NO₃⁻, as made Ni₂P/Ta₃N₅and Ni₂P/TaON display as high as 79% and 61% NO₃⁻conversion under 419 nm light within 12 h, which correspond to reaction rates per gram of 196 μmol g⁻¹ h⁻¹and 153 μmol g⁻¹ h⁻¹, respectively, and apparent quantum yields of 3–4%. Compared to 24% NO₃⁻conversion in Ni₂P/TiO₂, Ni₂P/Ta₃N₅and Ni₂P/TaON exhibit higher activities due to the visible light active semiconductor (SC) substrates Ta₃N₅and TaON. We also discuss two possible electron migration pathways in Ni₂P/semiconductor heterostructures. Our experimental results suggest one dominant electron migration pathway in these materials, namely: Photo‐generated electrons migrate from the semiconductor to co‐catalyst Ni₂P, and upshift its Fermi level. The higher Fermi level provides greater driving force and allows NO₃⁻reduction to occur on the Ni₂P surface.

    

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