Positive shift in the potential of photo-electrochemical CO2 reduction to CO on Ag-loaded boron-doped diamond electrode by an electrochemical pre-treatment
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Ag-loaded boron-doped diamond (BDD) electrodes are used for photo-electrochemical reduction of CO2 to CO. The advantage of the electrode would be highlighted by the CO2 reduction at more positive potentials than that for electrochemical CO2 reduction on Ag electrodes. In the present study, we achieved a positive shift in the potential of Ag-loaded BDD electrodes prepared by two steps: namely, a pre-treatment of the BDD surface by cathodic electrolysis in an acidic solution and electrodeposition of Ag co-catalysts. The effects of the pre-treatment on the crystal structure and the chemical states on the surface of BDD were investigated by spectroscopic analysis with Raman scattering and X-ray photoelectron. The pre-treated Ag-loaded BDD electrode exhibited a positive shift in the apparent onset potential (− 0.18 V) in the current–voltage (I–V) curves of a CO2-purged 25 mM Na2SO4 solution under irradiation by ultraviolet light (222 nm). These results were compared with the potential of an electrode based on as-prepared BDD (− 0.64 V) under the same conditions. We applied a potential of − 0.61 V and analyzed the formation of CO by gas chromatography to confirm a nFE greater than 70% for the pre-treated Ag-loaded BDD electrode. The I–V curves and CO production were also investigated in the absence of ultraviolet light and the Ag co-catalysts. We discuss the factors that contributed to the positive shift in the potential for photo-electrochemical CO2 reduction on Ag-loaded BDD electrodes.
KeywordsAg-loaded BDD CO2 reduction Hydrogenated structure Pre-treatment Gas chromatography Cyclic voltammetry
This work was supported by Japan Science and Technology (JST), ACT-C program. We thank Andrew Jackson, PhD, from Edanz Group (http://www.edanzediting.com/ac) for editing a draft of this manuscript.
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