Study on electrocatalytic $CO_2$ reduction and water oxidation using solar cell electricity

Abstract

The CZTSSe thin film was fabricated by chemical deposition method. Precursor solution was prepared by mixing metal acetate and thioacetamide in THF. Precursor solution deposited on Mo layer conducted $1^{st}$ and $2^{nd}$ heat treatment. After the process, the physical properties of thin film were examined XRD, UV-vis, SEM, EDS and AES analysis. To analyze photovoltaic property CdS/i-ZnO/ZnO:Al/Al grid layer fabricated on the CZTSSe layer. The fabricated CZTSSe solar cell was performed 0.27% of conversion efficiency with 0.162 V of open circuit voltage, $4.78 mA/cm^2$ short circuit current density and 43% of fill factor. For electrochemical $CO_2$ reduction, Cu pillar electrodes (Cu-2.5 h, Cu-5 h) were fabricated by using an electrodeposition method, which then catalytic activities and reaction mechanisms were investigated. The Cu-5 h electrode performed well with a 28 % Faradaic efficiency to formic acid at -0.5 V (vs. RHE). X-ray diffraction (XRD) analysis indicated that the enhanced catalytic activities were primarily attributable to the increased (111) facet, which is energetically favorable to produce HCOOH. Also, ultra violet photoelectron spectroscopy (UPS) and in situ electrochemical impedance spectroscopy (EIS) results suggested that the series of Cu pillar structure electrodes improved the electron transfer to adsorbed $CO_2$ due to the decreased work function of Cu pillar structure. For the simultaneous electrochemical $CO_2$ reduction and water oxidation system, electrodeposited Ag dendrite and Co-Pi electrode were employed, respectively. Also, several reaction condition was tested to optimize $CO_2$ reduction rate and supplement of proton derived from water oxidation. Total $CO_2$ conversion which was started from -2.5 V in two electrode system produced carbon monoxide and oxygen at cathode and anode, respectively. The each reactions were maintain for 4 hours without pH change. The maximum faradaic efficiency of total $CO_2$ conversion showed 70 % at -2.8 V