Research Synopsis

The research of our photochemistry group focuses on solar energy as one of the most promising forms of renewable energy and aims to solve the global crisis of climate change concerning our human survival.  We aim to transform cheap and ubiquitous substances including H₂O, CO₂, N₂, or lignin into valuable fuels or value-added chemicals such as H₂, CO, CH₃OH, NH₃, etc with sunlight and some “chemical magic”.  One of the most important advantages for the students being trained in our research group is getting to learn the “chemical magic”, a.k.a. the understanding of fundamental electron transfer processes through state-of-the-art spectroscopic techniques in our laboratory. Students and Postdocs in our photochemistry group will be immersed in the following research topics:

1.       Energy-demanding organic photoredox catalysis and the underlying photochemistry of visible light harvesting molecular photocatalysts

2.       Solar fuels production and the underlying photoinduced electron transfer mechanisms           

3.       Photoelectrochemical devices for artificial photosynthesis

Our independent research is also made possible through very fruitful collaborations:

·         Gerald J. Meyer, University of North Carolina at Chapel Hill (UNC), USA

·         Renato N. Sampaio, University of North Carolina at Chapel Hill (UNC), USA

·         Ludovic Troian-Gautier, UCLouvain, Belgian

·         Matthew V. Sheridan, Soochow University, China

·         Jianli Hua, East China University of Science and Technology, China

·         Baojiang Jiang, Heilongjiang University, China

·         Jia Guo, Fudan University, China

·         Zhang-Jie Shi, Fudan University, China

Ongoing Research Projects

1.  Consecutive Light Excitation Approach to Energy-Demanding Synthesis of Value-Added Chemicals

Inert chemical bonds such as C-H, C-Cl, N≡N, etc. require highly reducing or oxidizing reagents (E < -2 V or > 2 V vs. SCE) to initiate chemical transformations to value-added chemicals.  Excited states of typical photocatalysts such as ruthenium or iridium based metal complexes are incapable of achieving such extreme redox potentials.  Our research group set out to use small organic photocatalysts that could consecutively absorb multiple photons and reach super-photooxidants or reductants.  Our current achievements include using N-phenylphenothiazine (PTH) photocatalyst to do one electron oxidation of chloride and activate C(sp³)-H bonds for the synthesis of functionalized alkanes; using hybrid structure of perylene diimide (PDI) with ZrO₂ nanoparticles to activate aryl C-Cl bonds or CO₂ reduction catalyst at low catalytic concentrations.

Selected Publications:

1)     Zhao, Z.; Li, J.; Yuan, W.; Cheng, D.; Ma, S.; Li, Y.;Shi, Z.; Hu, K.*, Nature-Inspired Photocatalytic Azo Bond Cleavage with Red Light. J. Am. Chem. Soc. 2024, 146 (2), 1364-1373.

2)     Zhao, Z.; Niu, F.; Li, P.; Wang, H.; Zhang, Z.; Meyer, G. J.*; Hu, K.*, Visible Light Generation of a Microsecond Long-Lived Potent Reducing Agent. J. Am. Chem. Soc. 2022, 144, 7043-7047.

3)       Li, P.; Deetz, A. M.; Hu, J.; Meyer, G. J.*; Hu, K.*, Chloride Oxidation by One- or Two-Photon Excitation of N-Phenylphenothiazine. J. Am. Chem. Soc. 2022, 144, 17604-17610.

4)     Li, P.; Liu, R.; Zhao, Z.; Niu, F.; Hu, K.*, Lignin C–C bond cleavage induced by consecutive two-photon excitation of a metal-free photocatalyst. Chem. Commun. 2023, 59, 1777.

2.   Photoelectrochemical Cells (PEC) for Artificial Photosynthesis (Liquid Sunlight)

The sun is the most abundant renewable energy upon which a sustainable society can be built.  Currently, harvesting 1/7000 of the total solar energy reaching the surface of our earth will suffice the entire energy demand of our human society.  Natural photosynthesis in which CO₂, water, and sunlight are converted into carbohydrates and dioxygen gives us a perfect example to learn the trick of storing solar energy into high energy chemical bonds.  Our research group set out to use visible light absorbing semiconductor based photoelectrodes for the construction of photoelectrochemical cells (PEC) to mimic natural photosynthesis.  Our current efforts include using modified bismuth vanadate as the photoanode material for water, glycerol oxidation or organic C-H functionalization; using dye-sensitized photoelectrodes for the construction of tandem cells for total water splitting.

Selected Publications:

1)     Hu, K.; Sampaio, R. N.; Schneider, J.; Troian-Gautier, L.; Meyer, G. J.* Perspectives on Dye Sensitization of Nanocrystalline Mesoporous Thin Films. J. Am. Chem. Soc. 2020, 142 (38), 16099-16116.

2)     Niu, F.; Zhou, Q.; Han, Y.; Liu, R.; Zhao, Z.; Zhang, Z.; Hu, K.*, Rapid Hole Extraction Based on Cascade Band Alignment Boosts Photoelectrochemical Water Oxidation Efficiency. ACS Catal. 2022, 12,16, 10028-10038.

3)     Niu, F.; Zhang, P.; Zhang, Z.; Zhou, Q.; Li, P.; Liu, R.; Li, W.; Hu, K.*,  Ultrathin corrugated nanowire TiO2 as a versatile photoanode platform for boosting photoelectrochemical alcohol and water oxidation. J. Mater. Chem. A, 2023, 11, 4170.

4)     Han, Y.; Chang, M.; Zhao, Z.; Niu, F.; Zhang, Z.; Sun, Z.; Zhang, L.; Hu, K.*, Selective Valorization of Glycerol to Formic Acid on a BiVO4 Photoanode through NiFe Phenolic Networks. ACS Appl. Mater. Interfaces 2023, 15, 9, 11678–11690

5)     Shen, L.; Zhang, S.; Ding, H.; Niu, F.; Chu, Y.; Wu, W.*; Hu, Y.; Hu, K.*; Hua, J.*, Pure organic quinacridone dyes as dual sensitizers in tandem photoelectrochemical cells for unassisted total water splitting. Chem. Commun. 2021, 57, 5634-5637

Photochemical characterization