The Study Of Photoelectrocatalytic Reduction Of CO₂Based On The Electrode Of CdSeTe/TiO₂NTs

In recent years, energy crisis and global warming are two major problems that influencethe human sustainable development. Serious environmental problems such as bad climatesand rising sea levels are caused by masses of CO₂released from fossil fuels burning. So,reducing CO₂emissions and developing renewable energy systems which are environmentalfriendly and non-fossil fuel type have become a hot research topic. As the potential carbonresource, some relative technologies about catalytic hydrogenation transforming CO₂toalcohols, hydrocarbons have been intensively reported. The key problem is where thehydrogen coming from. In the traditional methods, such as heterogeneous and homogeneouscatalytic hydrogenation at high temperature and pressure, CO₂catalytic copolymerization, thehydrogen derived from fossils. The entire process is less practical and applicable. However,the hydrogen is from H2O in photocatalytic （PC） reduction and electrocatalytic （EC） reductionCO₂process, they are renewable energy methods with clear and environmental friendly way.So the above two methods are advanced processing techniques with excellent PC and ECreduction performance for CO₂.In1979, it was reported for the first time that TiO₂powder can PC reduction of CO₂tostudied most extensively and thoroughly, including morphology, crystalline phase andmodification et al.. Compared with TiO₂nanoparticles and nanofilms, TiO₂nanotubes （TiO₂NTs） have larger specific surface, more active sites and higher catalytic activity, so TiO₂NTsget more attention. Whereas, the wide band gap （Eg=3.2eV） of TiO₂decides that it only canbe excited by light of wavelength shorter than385nm, this point limits its practicalapplication greatly. As we all known, ultraviolet light （λ≤420nm） accounts to less than4%in the whole solar spectrum, while the visible light is more than45%. In order to highefficiently utilize the solar radiation, it needs to develop the catalysts with stability, highlyactivity, low-cost and strong visible light response.In this paper, we have studied the photoelectric integration catalytic reduction of CO₂reduction with CdSeTe/TiO₂NTs, which could be divided into three aspects as follows:1. The CdSeTe nanosheets were assembled to the TiO₂NTs by hydrothermal method, theCdSeTe NSs/TiO₂NTs catalysis was obtained. It showed that the CdSeTe was sheetmorphology and distributed on the TiO₂NTs surface uniformly according to the SEM andTEM testing. Measured by UV-vis DRS, it got the band gap of the as-prepared catalysis,1.48eV. XPS showed its valence band located at1.02eV. Under light irradiation, the PECreduction performance for CO₂had a significant improvement compared with TiO₂NTs, it expressed as the great increase of current density. In the PEC reduction CO₂process,methanol was the major product identified by gas chromatography, and the excellentreduction mechanism was explained from the following three aspects: energy band match,electron high transport ability and the material’s stability.2. By using the method of photoelectro-deposition, CdSeTe NPs/TiO₂NTs catalysis wasobtained. It showed that the CdSeTe was nano-particles with grain diameter about85-150nmand distributed on the TiO₂NTs surface uniformly according to the SEM. Measured byUV-vis DRS, it got the band gap of the as-prepared catalysis,1.24eV. The band gap wasfurther narrowed so that the Sunlight utilization was further improved. The introduction of theCdSeTe NPs not only increased the light active sites, but also reduced the band gap of thecatalysis. And the efficiency of photoelectrocatalytic CO₂reduction was increased byreducing overpotential of photoelectric catalytic reduction of CO₂.3. The SnO₂was assembled to the TiO₂NTs by hydrothermal method, the SnO₂-CdSeTeNPs/TiO₂NTs catalysis was obtained. By introducing SnO₂into the catalyst, excellentelectrocatalytic performance of SnO₂was also transplanted into the catalyst. In the experiment,after loaded SnO₂, the value of band gap has a slight increase from1.24eV to1.53eV, sothere was little loss in absorption of visible light. And electro-catalytic property was improveda lot.