Chemical Reaction Engineering Group (CREG) N01-Faculty of Chemical Engineering

1. Carbon Dioxide Reduction with Hydrogen Using Photonanocatalyst Nor Aishah Saidina Amin Chemical Reaction Engineering Group (CREG) N01-Faculty of Chemical Engineering Universiti Teknologi Malaysia UTM 81310 Johor Bahru, Johor Malaysia. noraishah@cheme.utm.my www.cheme.utm.my

2. Presentation Outline • Background of Study • Research Scope • Methodology • Results and Discussions • Conclusions • Acknowledgement

3. Background Majour contributors Global anthropogenic greenhouse gas emissions broken down into 8 different sectors. [http://en.wikipedia.org/wiki/Greenhouse_gas]

4. Background • Energy consumption has been increasing with world population • Fossil fuels are the main source of energy supply • Reserves of fossil fuel is fossil depleting Combustion of fossil fuels generates greenhouse CO2 Fossil fuel Combustion Greenhouse Gas CO2 Energy Crisis and Global Warming

5. Mitigation of Greenhouse Gas CO2 How? • How CO2 can be re-utilized easily and efficiently • How CO2 can be recycled or converted to fuels

6. Recycling of CO2 to Fuels Conversion of Carbon Dioxide Reforming (CO, H2) Electrochemical (EtOH, HCOOH, CO) Biological (EtOH, sugar, CH3COOH) Photocatalysis (CO, CH4, HC, MeOH, HCOOH) • Required biocatalyst • Required very specific conditions • Specific bioreactors • Short life time of biocatalyst • Workable under solar energy • Economical process • Required normal temp and pressure • Sustainable process • High stability of catalysts • Required electricity for the process • Required high voltage and cause fouling on electrode surface Plasma reforming Thermal reforming • Required higher temperature and pressure • Thus, instability of catalysts and uneconomical 6

7. Photocatalysis System Reducing Agent Semiconductor Material Photocatalytic Reactor • Have good photoactivity • Higher charger production • Lower charges recombination • Can easily be oxidized • Can reduced CO2 • Can help to produce • desire products • Higher photonic Efficiency, • higher illumination area Efficient Phototechnology for CO2 Reduction

8. What we are Offering?? Hydrogen Reductant PlasmonicPhotoCatalysts Monolith Photoreactor

9. Hydrogen Reducing Agent • Hydrogen is good reducing agent for CO2 conversion via RWGS reaction • Syngas (CO and H2) can be used for F-T process • CO2 reduction with H2 can also be produced hydrocarbons in single step. • H2 for CO2 reduction can be obtained from water splitting (RWGS reaction) Single step F-T process

10. Monolith Photoreactor • It has microchannels of different shape and sizes • Light distribution is effective over the catalyst surface. • Larger surface area to reactor volume. • Catalyst loading is higher with enhanced stability. • Very suitable for systems operating in gas- solids. • Larger conversion with improved selectivity. • Higher quantum efficiency • Higher light distribution over the catalyst Monolith • Honeycomb, foam or fibers structure • Channels have square, circular, and triangular • Density varies from 9 to 600 cells per square inch (CPSI) • Higher void fraction (65 to 91 %) compared to packed bed catalyst (36 to 45 %)

11. Plasmonic Au/TiO2 Photonanocatalyst LSPR of Au • When the incident light is (in the range of LSPR) absorbed by Au- metal NPs, electric filed (e-/h+ ) is produced (Fig. a) • Plasmonic electrons are transferred to TiO2 CB band for its activation (Fig. B) (a) • Efficient separation of electrons • Efficient CO2 reduction via SPR effect • Higher efficiency for trapping electrons • Au can enhance efficiency under UV and visible light (b) TiO2

12. Experimental Setup Monoliths Schematic of Monolith Reactor Experimental Rig

13. Catalyst Preparation and Coating Hydrolysis Ti (C3H7O)4 + isopropanol Acetic acid + isopropanol Au-loading Aging Gold chloride + isopropanol Dip-coating Monolith Drying and Calcination Dried at 80 oC for 24 h Calcined at 500oC for 5h @ 5oC/min

14. SEM and TEM Analysis TEM (Au/TiO2) SEM Front view Side View TiO2 Au/TiO2 • TEM images of Au/TiO2 exhibit uniform particle size and mesoporous structure of TiO2 • TiO2 d-spacing confirmed anatase TiO2. • Uniform coating of catalysts over the monolith surface • TiO2 particles are spherical in shape and uniform size • Au/TiO2 have mesoporous structure

15. XRD, BET and UV-Vis Analysis (a) (b) XRD A A=anatase BET A A A (c) • Anatase phase in TiO2 and Au/TiO2 samples • N2 adsorption-desoprtion plots show isothersms of type IV, confirming mesoporous materials of TiO2 and Au/TiO2 • UV-Visible analysis confirmed Plasmonic effect in Au/TiO2 catalyst Plasmon effect UV-Vis

16. Summary of Analysis Nanocatalyst Table 1 Table 2 • Au has no effect on BET surface area • Au has no effect on Crystallite size • Band gap energy shifted to visible region in Au/TiO2 • Gold was present over TiO2 in metal state

17. Photoactivity Test of Continuous CO2 Reduction to CO (a) CH4 production (a) CO production Fig. Effects of Au-loading and irradiation time on CO2 reduction with H2 at CO2/H2 ratio 1.0, molar flow rate 20 mL/min, and temperature 100oC; (a) CO production, (b) CH4 production. • Plasmonic Au/TiO2 registered significantly enhanced CO production activity over irradiation time • Optimum Au-loading of 0.5%Au was determined • Maximum yield of CO was 12445 µmole g-catal.-1 • Steady sate process achieved after 2h of irradiation time. • Maximum production of CH4 initially • CH4 production decreased due to photo-oxidation back into CO2 by O2 produced over catalyst surface • Saturation of catalyst sites with intermediate species or deactivation of catalyst • photo-reduction of products back to CO2.

18. Summary of Results 0.5% Au/TiO2 CO selectivity 92% to 99% 318 fold TiO2 Fig. (b) Selectivity of products over Au/TiO2 catalysts. Fig. (a ) Yield rates of products over Au/TiO2 catalysts

19. Catalyst Stability Test b= hydrocarbons production a= CO production CH4 C2H6 • In the cyclic runs over prolonged irradiation time, higher stability of catalysts • In second and third cycles, photoactivity slightly reduced • Decreased in photoactivity of Au/TiO2 catalyst was possibly due to active sites blockage with intermediate species.

20. Conclusions • Enhanced efficiency of monolith photoreactor for CO2 reduction to fuels • Efficient CO2 reduction with H2 to CO and HCs over Au/TiO2. • Yield of CO production over Au/TiO2 increased to 318 times higher than TiO2 • Selectivity of CO production reached above 99% by Au • Enhanced Au/TiO2 activity was due to plasmonic effect • Efficient trapping of electrons and inhibited charges recombination by Au-metal • Tests revealed prolonged stability of Au/TiO2 in cyclic runs.

21. Acknowledgements • Ministry of Higher Education (MOHE) Malaysia for financial support under NanoMite LRGS (Long-term Research Grant Scheme , Vot 4L839), • Universiti Teknologi Malaysia (UTM) for the RUG (Research University Grant, Vot 02G14) and • FRGS (Fundamental Research Grant Scheme, Vot 4F404).

22. THANK YOU FOR YOUR ATTENTION Chemical Reaction Engineering Group (CREG) N01-Faculty of Chemical Engineering UniversitiTeknologi Malaysia UTM 81310 Johor Bahru, Johor Malaysia. noraishah@cheme.utm.my www.cheme.utm.my/staff/noraishah