(6cj) Accelerating Net-Zero Carbon Emissions By Electrochemical Catalysis: Understanding and Controlling the Reactions at Interfaces

Overview. Electrochemical conversions of CO₂ to C_xH_yO_z, H₂O to H₂, and N₂ to NH₃ /NO^3‒are promising technologies for future energy conversion and storage processes. These electrochemical catalytic reactions all involve the transfer of multi-electrons and protons to or away from the absorbed substrates. Unfortunately, high activation energies as well as the possibility of undesired side products are caused by the multi-step of electrons/protons transfers. My research interest lies in elucidating the operative mechanisms of these important electrochemical reactions with an emphasis on understanding the electrocatalyst surface chemistry including the reaction pathways, adsorbate/adsorbate interactions, field effects, ligand effects and many others which influence the efficiency and selectivity of these reactions. Electrocatalyst materials capable of efficiently driving these important reactions can thus be designed and synthesized based on the understanding of the mechanistic details. The insights gained should further be useful in any field that deals with the careful control of electron/proton transfers, for instance electrochemical biomass conversion and organic synthesis.

Overall Goal: Develop effective electrocatalysts and processes to produce fuels and chemicals by renewable electricity without carbon emissions. Specific aims are set to achieve these goals: (a) understand kinetics and reaction mechanisms on the electrode surface, (b) develop new catalysts based on the kinetic modelling and activity descriptor, (c) develop processes/reactors to explore economically feasible paths to sustainably produce chemicals and fuels.

Scientific Goal: Understand the reaction mechanism at the interfaces of solid-liquid and/or gas-solid-liquid, and further control the reaction environment of the active sites to achieve high performance.

The first three projects I intend to work on will be: (i) electrochemical CO₂ or cascade CO₂/CO reduction to beyond 2e^- products; (ii) Electrochemical synthesis of NH₃ and NO₃^‒ from N₂ and H₂O, and exploring the reaction intermediates on the surfaces; (iii) Develop new electrocatalysts for the selective conversion of organic substrates to value-added products under mild conditions. Over time, these will evolve to include additional reactors and catalytic systems design that provide a set of sustainable methods to produce commodity chemicals and fuels.

Successful Proposals:

The Swedish Knut and Alice Wallenberg Foundation Postdoctoral Scholarship Program at Stanford, 2016.

PhD Research. My PhD thesis work was conducted under the supervising of Prof. Licheng Sun at KTH Royal Institute of Technology, Sweden. It introduced innovative concepts for the rational design of molecular catalysts based on comprehensive kinetic and mechanistic studies. Of particular relevance, I demonstrated that radical coupling of the metal oxide intermediates is the rate limiting step for water oxidation on ruthenium complexes with axial imidazole/DMSO ligands. Based on this finding, more efficient catalysts were obtained through the rational design of the axial ligands which facilitate the radical coupling pathway.^1-7 The mechanistic insights gained while working on homogeneous catalysis inspired me to develop a new heterogeneous nickel-hydroxide catalyst with remarkable activity for the oxygen evolution reaction.⁸ Later, I also introduced a polymer dots as an effective photocatalyst for hydrogen evolution, opening the door for the use of organic polymer dots as photocatalysts for the green hydrogen production from water.⁹

Postdoctoral Research: During my postdoctorate in Prof. Thomas. Jaramillo’s group at Stanford, I extended my primary goal to develop electrocatalysts that can selectively reduce CO₂ into liquid fuels. I started with CO reduction under alkaline conditions, important selectivity trends on the function of electrode surface area and electrode potentials were established based on comprehensive kinetics analysis, outlining key principles for designing CO and CO₂ electrolyzers that are able to produce valuable products with high energy efficiency.^10-11

Teaching Interests: I look forward to the exciting opportunity to mentor students of all backgrounds in order to help them develop their potentials to the fullest. I am capable of teaching all the core chemical engineering courses that offered by the department based on my education background, besides my research background ensures me the ability to teach all levels of kinetics, reaction engineering, physical chemistry, and data analysis courses. My TAing experience also gives me confidence in teaching chemistry and chemical engineering laboratory courses. Moreover, I would be very interested in developing courses on Electrochemical Energy Conversion Systems that introduce principles, current research efforts, existing challenges and opportunities. Students would learn in this course how to design experiments and solve problems in fuel cells, batteries, (photo)electrochemical cells using equivalent circuits of physical significance.

Selected Publications:

1. “Towards Controlling Water Oxidation Catalysis: Tunable Activity of Ruthenium Complexes with Axial
   Imidazole/DMSO Ligands”
   L. Wang, L. Duan, B. Stewart, M. Pu, J. Liu, T. Privalov, L. Sun. J. Am. Chem. Soc. 2012, 134, 18868-18880.
2. “Visible light-driven water oxidation catalyzed by mononuclear ruthenium complexes”
   L. Wang, L. Duan, L. Tong, L. Sun. J. Catalysis. 2013, 306, 129-132.
3. “Highly Efficient and Robust Molecular Water Oxidation Catalysts Based on Ruthenium Complexes”
   L.Wang, L.Duan, Y. Wang, M. Ahlquist, L.Sun. Chem. Commun., 2014, 50, 12947.
4. “Sensitizer-Catalyst Assemblies for Water Oxidation”
   L. Wang, M. Mirmohades, A. Brown, L, Duan, F. Li, Q. Daniel, R.Lomoth, L. Sun, L. Hammarstöm,. Inorg.
   Chem., 2015, 54 (6), pp 2742–2751
5. “Electrochemical Driven Water Oxidation by Molecular Catalysts in situ Polymerized on the Surface of Graphite
   Carbon Electrode”
   L. Wang, K. Fan, Q. Daniel, L.Duan, F. Li, B. Philippe, H. Rensmo, L. Sun. Chem. Commun., 2015, 51, 7883.
6. “Nickel (II) Complex as an Electrocatalyst for Water Oxidation”
   L. Wang, L. Duan, R. Ambre, Q. Daniel, H. Chen, J. Sun, B. Das, A. Thapper, J. Uhlig, P. Diner, L. Sun. J.
   Catalysis. 2016, 335, 72–78.
7. “Towards Efficient and Robust Anodes of Water splitting Device: Functionalizing Electrodes with Ru catalyst by
   in situ polymerization”
   L. Wang, K. Fan, H. Chen, J. Sun, L. Sun. Catalysis Today, 2017, 290, 73.
8. “Promoting the Water Oxidation Catalysis by Synergistic Interactions between Ni(OH)2 and Carbon Nanotube”
   L. Wang, H. Chen, L. Duan, Q. Daniel, B. Philippe, H. Rensmo, L. Sun. Advance Energy Materials, 2016, 201600516.
9. “Organic Polymer Dots as Photocatalyst for Visible Light-Driven Hydrogen Generation”
   L. Wang, R. Fernández-Terán, L. Zhang, D. Fernandes, L. Tian, H. Chen and H. Tian. Angew. Chem. Int. Ed.
   2016, 55(40):12306-10.
10. “Electrochemical CO Reduction on Poly-Cu: Effects of Potential and pH on Selectivity toward Multicarbon and
    Oxygenated Products”
    L. Wang, S. A. Nitopi, E. Bertheussen, M. Orazov, C. G. Morales-Guio, C. Hahn and T. F. Jaramillo. ACS
    Catalysis., 2018, 8, 7445–7454.
11. “Electrochemically converting carbon monoxide to liquid fuels by directing selectivity with electrode surface area”
    L. Wang, S. A. Nitopi, E. Bertheussen, M. Orazov, A. Wong, D.C. Higgins, C. G. Morales-Guio, C. Hahn and T. F. Jaramillo. Nature Catalysis, 2019, DOI: 10.1038/s41929-019-0301-z.