Catalysis for CO2 conversion
With the growth in population and economy, there is an increase in energy demand for industry and domestic use. Unfortunately, the usage of fossil fuels also leads to the emissions of greenhouse gases, including carbon dioxide (CO2), which contributes to global warming. Nevertheless, with the increase in research focus, it is possible to convert anthropogenic carbon dioxide into fuel. Carbon dioxide utilisation, when done efficiently and sustainably, would lessen dependence on fossil fuels and also reduce the amount of CO2 emitted.The Particle and Catalysis Research Group (PartCat) has been focusing on the utilisation of CO2 and investigating ways to improving a range of processes for converting CO2 into valuable products. Major research projects currently being undertaken include:
- Solar + Thermal CO2 Methanation
- Dry CO2 Reforming of Methane
- Direct Electrocatalytic CO2 Reduction
- Converting CO2 to fuels using plasma
Solar + Thermal CO2 Methanation
The conversion of CO2 and hydrogen to methane (often known as Sabatier reaction) is an exothermic reaction, which requires a catalyst to aid the breakdown of the stable CO2 molecule. Noble metal catalysts based have displayed very high activities for the process, but due to high noble metal cost, this has dictated the development of transition metal alternatives. The Particles and Catalysis Research Group has focused primarily on developing cheap, transition metal-based catalysts.
CO2 + 4H2 → CH4 + 2H2O
In a previous study, PartCat have found Ni supported on CeO2/TiO2 composites is able to achieve high conversion of CO2 to methane, with a near 100% selectivity. Furthermore, using light to illuminate did not improve the CO2 conversion at a given temperature but was able to induce heating of the reaction chamber thus reducing the energy input needed to heat the reactor. This suggests that the use of light as a tool for heating has potential.
Building on previous works, PartCat has developed an integrated system, where photothermal technology is used to run the methanation reaction. Solar heating is the main driving force, with a solar furnace able to heat the sample holder up to 700°C. The sample holder can then be supplied with CO2 and hydrogen, which is converted into methane and can be integrated with the existing natural gas network. Initial testing of this system at UNSW with a Ni-based catalyst has demonstrated that very high CO2 conversion can be achieved, with virtually 100% selectivity towards methane.
Photothermal conversion of carbon dioxide has only been investigated recently and thus there are numerous unknown areas to explore. The project will investigate into the development of novel catalysts for the photothermal conversion of carbon dioxide to methane. Metals will be supported on inert and semiconductor supports to increase the efficiency of the reaction and to understand the interaction between the metal and support.
Level of difficulty: Challenging
Suitable for: Chemical Engineers and Industrial Chemistry students.
Students working in this project will be supervised by Dr Emma Lovell, Dr Jian Pan (Jeffry) and Scientia Prof Rose Amal. Please contact one of the academic supervisor to find out more about this project.
Dry (CO2) Reforming of Methane
Dry reforming (or CO2) reforming is a process which converts the two largest greenhouse gasses (CO2 and methane) into a valuable product called synthesis gas. The Particles and Catalysis Research Group has focussed in this area of research and has developed key specialisations. Both companies Linde and Sasol have shown this process to be viable at an industrial scale.
CO2 + CH4 → 2H2 + 2CO
A catalyst is used to boost conversion and overcome the energy requirements of the reaction. Typical dry reforming catalysts are based on transition metals such as cobalt (Co) or nickel (Ni), which have limited activity and stability. The addition of plasmonic metals, which respond to light illumination by generating electrons or localised heat, is a potential pathway for improving the performance of catalysts towards thermal conversions such as dry reforming. The proposed study will investigate the addition of a range of plasmonic metals (eg. Au, Cu, Pd, Ag) on supports (SiO2 and Al2O3). The effect of the plasmonic metal inclusion on catalyst activity, stability and selectivity will be examined, with the impact of light irradiation on the temperature requirements of the reaction also evaluated.
The enhancement of dry reforming catalysis with the plasmonic effect is an understudied field of research. While the limitations of transition metals in dry reforming are well known, studies which investigate the addition of plasmonic metals to promote the reaction under light illumination have not been carried out. The proposed research project will examine whether the addition of plasmonic metals (Au, Cu, Ag, Pd) via flame spray pyrolysis can enhance catalyst performance towards the dry reforming reaction under light illumination.
The flame spray pyrolysis is a rapid and single-step method for producing high surface area metal oxides which can be readily scalable. The team has demonstrated that highly active dry reforming of methane catalysts based on Co and an Al2O3 support can be synthesised via flame spray pyrolysis method. When doped with a small amount of La, the Co/Al2O3 materials are able to achieve stable conversion of 85-90% at an operating temperature of 700°C. To reach 700°C, this can be achieved using solar collector, which would also in turn reduce the energy required for heating.
Students working in this project will be supervised by Dr Emma Lovell, A/Prof Jason Scott and Scientia Prof Rose Amal. Please contact one of the academic supervisor to find out more about this project.
Direct Electrocatalytic CO2 Reduction
Another promising route of CO2 reduction is via electrochemical reduction using catalysis. This method mimics photosynthesis. Electrochemical CO2 reduction reactions (CO2RR) can be carried out in ambient conditions through the application of external bias and provides the opportunity to be coupled with electricity generated from renewable energy resources.
It is generally accepted that ideal electrochemical CO2 reduction reactions catalysts should possess the following characteristics:
- high product selectivity,
- long term stability,
- large current density and
- low costs.
A drawback to most electrocatalysts is high overpotentials requirements and typically this exhibit a trade-off between selectivity and current density. To circumvent such challenges, in-house PartCat have developed three-dimensional and porous Ag Foam electrodes that converts CO2 to CO. The next step is to further minimize catalyst costs through fabrication of metal-free Graphitic Carbon Nitride/Carbon Nanotube Composite catalysts and further improve the performance of the catalyst through defect engineering. This catalytic performance is among the highest of metal-free catalysts and is even on par with the benchmarked metallic catalysts.
Most of the electrodes used in the electroreduction of CO2 are the in the above mentioned form of metal plates, metal granules, or electrodeposited metals on a substrate. However, due to low solubility of CO2 in water under ambient conditions, the reaction rates and current densities of CO2RR are limited by mass transfer of CO2 from the bulk to the solid electrode surface. To improve the reduction process, Partcat has developed a gas diffusion electrodes (GDE) to improve mass transfer limitations across the gas liquid interface and to the catalyst surface. A GDE is a porous composite electrode made of polymer bonded catalyst particles on a carbon support. As GDE can be operated at higher current density, exhibiting high porosity and partial hydrophobicity, GDEs form a characteristic gas-solid-liquid three phase interface, which promote homogenous distribution over catalyst surface.
The aim of this project is to optimized the catalyst performance and test them using GDE system to improve the production rate of alcohol, so to make this technology financially viable.
Students working in this project will be supervised by Dr Emma Lovell, Dr Rahman Daiyan and Scientia Prof Rose Amal. Please contact one of the academic supervisor to find out more about this project.