A Study Of Photoelectric Synergy Reduction Of CO₂ Based On SiC NWs Modified Electrode

The core of photoelectric catalytic reduction of CO₂ is that prepared photoelectric catalysis material has high catalytic activity and electrochemical stability for a long time of photoelectric catalysis, and CO₂ molecule is the dipole moment of zero, three atomic linear structure, the good stability, but it must be activated to participate in a variety of reactions, so it's the top priority that find a suitable photoelectric reduction catalyst. SiC has high temperature resistance, corrosion resistance, great strength, good heating conduction performance and other significant advantages, It's almost the most negative potential of semiconductor material, and nanometer SiC has significantquantum size effect, which make the band gap grow wider, valence band potential grow more positive and the conduction band potential grow more negative, when SiC is enough energy lighted, it's excitated togenerateelectron-hole pair of having strong oxidation and reduction ability, therefore SiC can serve as a kind of excellent photoelectric catalyst carrier.Although the SiC have certain advantages in the photocatalytic reduction and mechanical performance, etc, it has low selectivity, poor electrical conductivity and general electric catalytic reduction ability of CO₂, so we can improve the efficiency of photoelectric catalysis by actting SiC as carrier and mixing with other active catalytic component participating in catalytic reaction.In order to be more limited use of sunlight and improved the utilization rate of catalysts for sunlight, we chose the Dy₂S₃ as modified material, Dy₂S₃ is a type of preferable high temperature thermoelectric materials, has a series of excellent performance, including high melting point, high photosensitivity, low electrical conductivity, and we can acquire an insulator or a metal conductor by changing the ratio of Dy:S. In various Dy₂S₃ structure, we find that Dy₂S₃ nanospherehas bigger surface area, order, good stability and easy to electron transfer, which is very suitable for involving in catalytic reduction reaction as a catalyst.We chose to use Ni as a modification of the metal, considering of the poor electrical conductivity and low catalytic efficiency of Si C, Ni doping compensates for lack of the conductivity of SiC, Ni has good electrical conductivity and electron transmissionability for photoelectrocatalysis, which can improve the activity of photoelectrocatalysis. To improve the electric catalytic activity and light energy utilization of catalyst after doping, thus which can improve the photoelectric catalysis performance.We first used a two-step metal-assisted chemical etching method to prepare Si NWs, then prepared of SiC by carbon thermal reduction, the line about 1 ?m, diameter of about 10 nm.The diameter of Dy₂S₃ is about 200 nm prepared in Square wave pulse deposition method, by loading to the SiC NWs, get SiC NWs/Dy₂S₃. Spherical Dy₂S₃ is found by SEM characterization, large surface area, more conducive to the adsorption of CO₂, thus improve the concentration of the reactants, improve its efficiency. We can know that the energy gap of Si C NWs/Dy₂S₃ significantly decreased from 2.8 eV to 2.1 eV by UV-vis DRS, which make the response of visible light and greatly improving the utilization efficiency of visible light.SiC NWs/Ni of prepared in pulse electrochemical deposition show round shape and diameter is about 100 nm by SEM, SiC NWs/Ni conductive ability has greatly improved by electrochemical impedance spectroscopy, which makes it more conducive to the electron transfer in photoelectrocatalysis and improve the photoelectrocatalysis activity. Experiments show that the loading Ni composite catalyst conductivity have greatly improved, resistance decreased significantly, the visible light absorption ability also rises slightly, which make the photoelectric conversion efficiency increase significantly, about 37.5%, high selectivity and methanol yield reached 4.1 mmol·L-1, which was 10 times higher than the single SiC.