The study of catalytic activity and reaction mechanism for the electrochemical reduction of CO2 on nanostructured Cu electrode.pdf

1、Extra emission of carbon dioxide (CO2) into the atmosphere, induced by human industrial activities, has been considered one of the primary causes in possible global warming due to the greenhouse effect, and also becoming

2、 an increasing concern in recent years.To address this issue, using electrochemical reduction to convert CO2 to low carbon fuels (methane, methanol, formic acid, and ethylene) represents a value-added approach to the sim

3、ultaneous generation of alternative fuels and environmental remediation of carbon emissions from the continued use of conventional fuels.Actually, it seems that the electrochemical reduction of CO2 would be an ideal ener

4、gy storage strategy in converting undesired CO2 into useful fuels using electricity from renewable sources such as hydro-electrical, solar, wind, tidal/wave, and ocean-thermal energy.
　　However, because of the slow el

5、ectrode kinetics of CO2 electroreduction, large negative overpotential is required which not only causes low energy efficiency but also induces high hydrogen evolution at such negative electrode potentials.Therefore, eff

6、ective electrocatalysts are highly desired in order to reduce overpotentials.
　　An effective electroeatalyst should be process the following three important factors, i.e.,activity, stability and the product selectivit

7、y.In this regard, the copper and its oxides have been
　　reported as the unique metal catalysts for CO2 electroreduction in aqueous electrolytes, since the component elements are plentiful and environmentally friendly

8、compared to Pb and Hg.However, the current efficiency of Cu was still limited by the relative large overpotential and, the selectivity of the production was also not satisfied.Additionally, the deactivation of Cu electro

9、des in CO2 reduction was found to be fast in aqueous solutions.Given all these unfavorable attributes, improvement in both the activity and stability of the Cu metal-based electrcatalysts for CO2 reduction are definitely

10、 essential in terms of practical applications.In fact, the performances of Cu-based electrocatalysts are strongly affected by the synthesis methods and the pretreatment procedures.This is because different methods and th

11、e pretreatment procedures could produce different morphologies with different microstructures.It has been reported that the thermal process could produce Cu2O film, which was then subsequently electroreduced into metal C

12、u surfaces, resulting in a stable catalyst with favorable energy-efficiency in CO2 reduction.On the other hand, different types of Cu-oxide electrocatalysts showed different current efficiencies in KHCO3 electrolyte, for

13、 example, the cuprous oxide (Cu2O) could give the highest efficiency.Although all Cu oxides could be reduced into metal Cu at negative potentials, different Cu oxides with different morphologies might give different surf

14、ace structures and surface areas, thus leading to different catalytic activity and stability as well as selectivity.
　　In this thesis, by a combined thermal-electroreduction approach, the hybrid Cu nanostructures from

15、 CuO-Cu2O oxide films prepared on Cu substrates was demonstrated to afford high catalytic activity for CO2 electroreduction.Because the Cu nanostructure contains two surface morphologies of sphericity-nanofibers, it is e

16、xpected to contribute the Cu electrode high surface area and active phase, which is superior active for CO2 electroreduction to previously
　　investigated, according to both onset potential and maximum current density