In this work, we have carried out on the photoelectrochemical and photochemical CO2 reduction reaction to have higher solar to fuel efficiency than 2.0%. To have such as high efficiency, several parameters for the thermodynamics and kinetics control were optimized in both approaches such as multi-electron shuttling process, reduction potential tuning, CO2 activation and multiple proton-coupled multiple electron transfer process as one pot reaction. Basically, CO2 reduction can be done combined with two water splitting reaction to produce maximum of electrons and protons to supply for CO2 reduction reaction. To have maximum of electrons and protons, we have tried with more than 30 kinds of photocatalysts and decided that BiVO4 was the best one as the pristine photocatalyst. By using BiVO4, we also added some more functional approaches to increase the efficiency of water splitting reaction via band gap engineering, crystal facet engineering and interface junction engineering. Based on the high efficiency of water splitting reaction, CO2 reduction reaction was carried out by using functional materials of the cathode. The multi-electron shuttling process was done by using rGO and and g-C3N4, which have large charge capacity, and studied with time resolved (TR) PL and TR-chornoamperometry. Reduction potential tuning was done by adjusting external bias potential and synthesizing rGO and g-C3N4 with optimized band energies. CO2 activation was done by using N-heterocyclic compounds such as poly(vinylpyridine) (PVP) and polypyrrole (PPy), which can activate reactant CO2 and lowering the energy level of transition state of the CO2 complex with PVP or PPy. The decreased activation energy can result in the faster kinetics of CO2 reduction reaction and it can be studied with Tafel plots and EIS plots at the different temperatures to calculate the decreased activation energy. To have one pot reaction of CO2 reduction, Nafion layer was coated on the surface of cathode to accelerate the proton diffusion into CO2 reduction site.

Thermodynamics and kinetics control of photoelectrochemical CO2 reduction reaction into liwuid fuels

2019 Spring National Meeting

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