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128th General Meeting of Korean Chemical Society Electrocatalyst for Water Oxidation and CO2 Reduction

Submission Date :
9 / 7 / 2021 , 16 : 16 : 22
Abstract Number :
Presenting Type:
Presenting Area :
Inorganic Chemistry - Past, Present and Future of Energy Chemistry in Korea
Authors :
Ki Tae Nam
Department of Materials Science and Engineering, Seoul National University, Korea
Assigned Code :
INOR1-1 Assigend Code Guideline
Presenting Time :
THU, 15 : 40
Water splitting and electrochemical CO2 conversion are regarded as the promising approaches towards environmentally sustainable energy schemes and carbon neutrality. The oxygen evolution reaction (OER) requires extremely high overpotential due to its slow reaction kinetics. The water oxidizing cluster in photosystem II, in the form of cubical Mn4CaO5 cluster, efficiently catalyzes water oxidation. Specific questions that we intensively focus for further applications include how to translate the underlying principles in Mn4CaO5 cluster into synthetic heterogeneous catalysts. Toward this vision, we have been developing a new catalytic platform based on sub-10 nm-sized Mn oxide nanoparticles to bridge the gap between atomically defined biological catalysts. In this approach, the local atomic geometry is controlled by the surface modification of the specific ligand and the heterogeneous atom doping, that enhance the catalytic activity and selectivity. Furthermore, we detected key intermediate species, Mn(IV)=O, based on comprehensive electrokinetic and in-situ spectroscopic analysis. We revealed unique water oxidizing mechanism mediated by Mn-oxide nanocatalysts different from bulk counterparts. We further conducted electrochemical impedance spectroscopy (EIS) analysis to understand various electrochemical processes in film-type OER electrocatalysts.
The products from electrochemical CO2 reduction reaction (eCO2RR) are inevitably limited to CO, HCOOH, C2H4, and so on. Recently, we proposed new strategies for CO2 utilization, redox neutral electrosynthesis into dimethyl carbonate and nitrate coupling into amino acid. Lowering the anodic overpotential and designing the membrane-separated system are also important determinants of the overall efficiency. We explored the possibility of using counterintuitive redox-neutral reactions in eCO2RR, to expand the product scope with higher efficiency. We combined three redox cycles in undivided cell so that the input electrons do not settle in CO2, but continue to flow through the electrolyte. The mechanistic study clearly shows that the formation of methoxide intermediates and the cyclic regeneration of the homogeneous Pd-catalyst by in-situ generated oxidants are important. In addition, we developed a new electrochemical method for synthesizing a C-N bond-containing molecule avoiding usage of cyanide and amines by harnessing nitrate (NO3-) as the nitrogen source in aqueous electrolyte. To synthesize glycine, we utilized oxalic acid as carbon source which can be obtained from eCO2RR, so that our approach can provide a new route for the utilization of anthropogenic CO2 and nitrate wastes.