cqvip:Photoelectrochemical and electrochemical reduction of CO2 into organic chemicals is promising for directly or indirectly transforming solar energy into chemical energy for further utilization. However,research on the electroactive species in these processes has been rather limited. In this work, we investigated possible electroactive species（CO2 or HCO3– ） involved in the electrochemical reduction of KHCO3 at elevated temperatures without CO2 bubbling. The results showed that CO, CH4, and C2H4 were produced after electrochemical reduction of 3.0 mol/L KHCO3 at elevated temperature on a Cu electrode even without CO2 bubbling, although their faradaic efficiencies were low（< 6 %）. Measurements for CO2 generation from the decomposition of HCO3– showed that elevated temperature and high HCO3– concentration strongly promoted this process. These results suggested that the in-situ produced CO2 from the decomposition of HCO3– was probably the electroactive species in the electrochemical reduction of HCO3– without CO2 bubbling. Changes of the Gibbs free energy, rate constant, and activation energy of the decomposition of HCO3– into CO2 were also investigated and calculated from the experimental data.
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