Dang Nguyen1 2 Yun Jeong Hwang1 2

1, Korea Institute of Science and Technology, Seoul, , Korea (the Republic of)
2, Korea University of Science and Technology (UST), Seoul, , Korea (the Republic of)

The conversion of carbon dioxide (CO2) to carbon monoxide (CO) on nanostructured silver or gold based electrocatalysts is an attractive process for a sustainable carbon cycle.1-2 However, industrial applications in massive scale of those metal catalysts can be limited due to their expensive cost. Zinc is a non-noble metal with low price and abundant reserves. Remarkably, bulk Zn metal was historically reported to catalyze for CO2-to-CO conversion, thus, Zn can be a promising metal to replace precious metals in the carbon dioxide reduction (CO2RR). In this study, a porous nanostructured Zn-based electrocatalyst was synthesized by reducing from its oxide (RE-Zn) to facilitate the activity for CO2RR. We discovered that the activation environment using saturated CO2 gas in electrolyte in pretreatment step plays a significant role in the fabrication of Zn-based catalyst to activate the high selection for CO production in CO2RR later. Meanwhile, using Ar gas bubbling in pretreatment environment instead CO2 gas can lead to less CO product of the Zn-based electrocatalyst. A Faradaic efficiency reached to 78.5% is achieved on the RE-Zn activated in CO2-bubbled KHCO3 electrolyte, which is about 10% higher than that of RE-Zn activated in Ar-bubbled electrolyte. Moreover, the CO2-pretreated catalyst in KCl electrolyte is highly effective in improving the selective CO production with a Faradaic efficiency of 95.3%. By high-resolution X-ray photoelectron spectroscopy studies of the interfacial surfaces on the high performing Zn electrodes, the higher amount of oxidized zinc states has been found. Thus, the active sites on RE-Zn for electrochemical CO2RR might be induced by the oxidized zinc states.3

1. Kim, H.; Jeon, H. S.; Jee, M. S.; Nursanto, E. B.; Singh, J. P.; Chae, K.; Hwang, Y. J.; Min, B. K., Contributors to Enhanced CO2 Electroreduction Activity and Stability in a Nanostructured Au Electrocatalyst. ChemSusChem 2016, 9 (16), 2097-2102. (DOI: 10.1002/cssc.201600228)
2. Kim, C.; Jeon, H. S.; Eom, T.; Jee, M. S.; Kim, H.; Friend, C. M.; Min, B. K.; Hwang, Y. J., Achieving Selective and Efficient Electrocatalytic Activity for CO2 Reduction Using Immobilized Silver Nanoparticles. Journal of the American Chemical Society 2015, 137 (43), 13844-13850. (DOI: 10.1021/jacs.5b06568)
3. Nguyen, D. L. T.; Jee, M. S.; Won, D. H.; Jung, H.; Oh, H.-S.; Min, B. K.; Hwang, Y. J., Selective CO2 Reduction on Zinc Electrocatalyst: The Effect of Zinc Oxidation State Induced by Pretreatment Environment. ACS Sustainable Chemistry & Engineering Just Accepted Manuscript. (DOI: 10.1021/acssuschemeng.7b02460)