Solid Oxide Fuel Cells for CO2 reduction

Transcription

1 Solid Oxide Fuel Cells for CO2 reduction Carbon Capture and U.lisa.on1 22/2/2017

2 Energy Materials Group at St Andrews Prof. John Irvine Well known in SOFC research Leads established group with long track record of new material synthesis and characterisadon Strengthening capabilides in process development beeer transfer and integradon of new materials into real world Current group size ~45 people Main area of research oxide materials for fuel electrodes Robust SOFC SOEC Reversible SOFC also Li baeery, catalysis, solar collecdon Carbon Capture and U.lisa.on 22/2/2017 2

3 Solid Oxide Device Operation Solid oxide fuel cell e - Solid oxide electrolysis e - Operate at high temperatures H 2 H 2 O O 2- O 2 H 2 O H 2 O 2- O 2 high ef/iciency no combustion no gas mixing Anode Electrolyte Cathode Cathode Electrolyte Anode fuel tolerant can be hydrocarbon fuelled can be used as input or output of CO 2 stream Images courtesy of Versa Power Systems Carbon Capture and U.lisa.on 22/2/2017 3

4 SOFC pure gas stream Produces pure CO 2 stream from HC fuels as the air and fuel kept separate all N 2 on air side only CO 2 and unused fuel and H 2 O pure, undiluted CO 2 stream H 2 Solid oxide fuel cell e - Good feed stock to CCS higher efficiency less CO 2 /kwh Scale? H 2 O Anode O 2- Electrolyte Cathode O 2 Carbon Capture and U.lisa.on 22/2/2017 4

5 Direct Carbon Fuel Cell (DCFC) Hybrid MCFC and SOFC Solid carbon fuel produces electricity and CO 2 carbon from biomass or coal High energy density High efficiency Carbon Capture and U.lisa.on 22/2/2017 5

6 DCFC Carbon Capture and U.lisa.on 22/2/2017 6

7 DCFC - CO 2 out Produces pure CO 2 stream as the air and fuel kept separate waste N 2 on air side only CO 2 and CO pure, undiluted CO 2 stream Good feed stock to CCS large CO 2 /kwh biomass? Scale? Carbon Capture and U.lisa.on 22/2/2017 7

8 Electrolysis - CO 2 in e - Fuel cells reversible feed in electricity get out fuel H 2 O H 2 O 2- O 2 High temperature advantage heat supply can replace electrical energy convert heat to fuel Cathode Electrolyte Anode Carbon Capture and U.lisa.on 22/2/2017 8

9 CO 2 Electrolysis CO 2 O 2- Air CO 2 CO + ½ O 2 also H 2 O H 2 + ½ O 2 plus many other side reactions Endothermic CO 2 + CO O 2- Air Cathode current collector 8% Yttria stabilized Zirconia (YSZ) Anode current collector Needs pure concentrated CO 2 stream different catalysts to H 2 producdon Carbon Capture and U.lisa.on 22/2/2017 9

10 CO 2 electrolysis catalysts SOEC CO 2 -N CO 2 -C O Current density / A cm -2 GDC impregnated LSCM/YSZ SOFC C e l l p o te n ti a l ( E ) / V Requirements for cathode material: High electronic and ionic conducdvity Good catalydc acdvity Resistance to carbon deposidon work in both reducing and oxidising atmospheres no need to add H 2 or CO good performance in either Carbon Capture and U.lisa.on 22/2/

11 ore porous external on. The application been reported for rm stability,132 but ng SOECs deserving en electrode microunique features of e the optimization dy a very promising hout the need for Other SOEC configuradons Air electrode: 2H2O - 4H+ + O2 + 4e! Proton conducdng electrolytes H - 2H + 2e direct CH4 producdon lysis production that electrolyzer cells. ting ceramic as a idification, based rating principle of contained in the 2 through a 60 mm thick BaCe0.5Zr0.3Y0.16Zn0.04O3!d electrolyte film, and reacted with CO2. The reactions happening at the air electrode and hydrogen electrode can be written as: 2 +! (4.1) (4.2) Hydrogen electrode: 2H+ + 2e! + CO2 - CO + H2O (4.3) 2 T.H. Shin et al. / Solid State Ionics xxx (2015) xxx xxx (a) 8H+ + 8e! + CO2 - CH4 + 2H2O (4.4) Protonic Single cathode: LSC CO2 Electrode reduced with (b) a conversion In their study, CO2 was successfully Electrode Electrolyte Steam CO2 rate of 65%. The main product was CO (61%), with smaller BCZYYZ amounts of (8%) and CH4 (1.2%), ashwell as unreacted CO 2 COH O / H H2Oin / H2 (29%). The CO2 conversion rate was much higher than 3% that H + reaction, 37%, and also signifithe reverse gas water shift (c) Double cathode: LS H 2+CO 135 cantly improved comparing with that for oxygen-ion SOECs, CO2 H O, O CO 2 only 11.5%, suggesting that electrochemical reduction with BCZYYZ proton-conducting- SOECs would be - an effective method e e + for CO2 reduction. It is- worth noting that CH4 was also 3% H 2O / H2 synthesized using the electrolysis process, with a better effi- Carbon Capture and U.lisa.on 22/2/ Fig. 1. a) Schematic diagram of CO2 reduction in proton conductor. b) Cell configuration using single cathode layer, LSCF + GDC and c)

12 Other SOEC configuradons Proton conducdng electrolytes electrochemical de-humidificadon of gas waste is pure H 2 Carbon Capture and U.lisa.on 22/2/

13 CO 2 SOEC Works well can form syn gas or even CH 4 proven in the lab, good perfomance Ideally on non-electrical CO 2 e.g. Cement or steel manufacture, pure heat system no point energedcally to do for power stadon beeer generate from renewable source displace generadon and store the unused methane Carbon Capture and U.lisa.on 22/2/

14 H21 Leeds City Gate InteresDng use of CCS Make Leeds a hydrogen powered town Fuel cell based CHP Clean enough H 2 for PEM? Carbon Capture and U.lisa.on 22/2/

15 SOFC Conclusion high efficiency and fuel flexibility can be used as a high purity source of CO 2 no N 2 diludon Direct Carbon Fuel Cell good use of carbon even more CO 2 produced problems with scale for CCS Carbon Capture and U.lisa.on 22/2/

16 Conclusion SOEC of CO 2 works for both proton and oxide fuel cells high temperature lowers electrical demand use of external heat source converts to syn gas or CH 4 needs development of catalysts not sensible for use with power stadons Carbon Capture and U.lisa.on 22/2/

17 Acknowledgements Ø JTSI Ø JTSI group Ø Funding organisations: Carbon Capture and U.lisa.on 22/2/