Sürdürülebilir kaynaklar kullanarak CO2 indirimi için katalyst geliştirme

Global warming is one of the major threats to humanity at present. The major cause is utilisation of fossil fuels which results in CO2 production. Present work establishes an understanding on the two molecules i.e. CO2 and H2O which are at the core of solution for the CO2 problem with an aim to develop catalytic surfaces for CO2 reduction reaction using sustainable sources. Researchers are working on developing surfaces which can help reduce these molecules effectively. All sorts of materials and techniques are under consideration from metals to semiconductors to nanomaterial and photo-electro-thermal catalysis. Our study points out one major finding, which is that the binding energy of an intermediate during any reduction process depends on the morphology of the material. Chapter 1 presents an overall picture of the CO2 dilemma with an emphasis on where we stand globally. It begins by first discussing thermodynamics and kinetics related to CO2 and H2O with a more subtle reading on hydrogen evolution reaction due to its simplicity. The same understanding can be applied to CO2 which results in more complex array of products such as methane, carbon monoxide, methanol etc. It also discusses the mechanism of HER and CO2R which is followed by text on plasma CO2 reduction. This chapter also deals with discussion of materials selection for reduction processes and also presents reports in tabulated form on the earth abundant materials presently being utilised for reduction purposes. Chapter 2 discusses HER on metallic copper nanowires, this is the first report on making nanowires using DBD plasma process. These nanowires are characterised by using SEM, XRD, XPS and Raman spectroscopy, followed by application in HER. These nanowires showed excellent performance in comparison to bulk copper surface form; by reaching the specific current density of 10mA/cm2 with an overpotential half the present value on bulk surfaces, also the exchange current density increase to at least six times. Chapter 3 presents findings on the use of metallic copper nanowires for CO2 reduction, we used a conventional two chamber electrolytic cell with separate counter electrode compartment to study CO2 reduced species. The products are analysed by using GC2014 with a column MS5A and nitrogen is used as carrier gas. We found that metallic nanowires are more selective to overall gaseous products as compare to their bulk counter part(flat copper surface). As the applied potential was increased to more higher values, the proportion of CH4 and CO is increased which is not observed in flat copper surface. Chapter 4 discusses the utilisation of DBD plasma technique for CO2 reduction on Cu and Ni oxide loaded supports (Al2O3 and SiO2). Inhouse system is built to carryout the CO2 reduction reaction. We observed the formation of saturated hydrocarbons on copper oxide loaded alumina while nickel oxide loaded silica showed preference for unsaturated hydrocarbons. Chapter 5, presents details on the use NiS and CuS for HER. Both surfaces after synthesis are treated with plasma and showed altered morphology. On comparison between plasma and non plasma treated metal sulphides, there is almost 100mV difference in overpotential to reach specific current density. In the end, main conclusions and future work are listed followed by references used in this study. Overall, in this thesis, new surfaces and techniques are evaluated for energy conversion processes with a goal of efficient energy conversion and we found that metallic copper nanowires are more efficient then bulk copper surface during HER reaction, the overpotential required to reach specific current density decreased by half; when metallic nanowires are used instead of bulk copper surface. When the same nanowires are tested for ECO2R, 30% increase in overall gaseous product is observed. During plasma reduction of CO2 on metal-oxide loaded supports, it is concluded that CuO loaded samples are selective towards saturated hydrocarbons while NiO loaded samples are selective towards unsaturated hydrocarbons with a total CO2 conversion efficiency of up to 30%.