Development ofTubular Proton Conducting Electrolysers Einar Vøllestad 2 , M.L. Fontaine 1 , C. Denonville 1 , R. Strandbakke 2 , J.M. Serra 3 , D.R. Beeaff 4 , C. Vigen 4 and T. Norby 2 1 SINTEF Materials and Chemistry, 2 University of Oslo, 3 CSIC, 4 CoorsTek Membrane Sciences AS
Development ofTubular Proton Conducting Electrolysers Einar Vøllestad 2 , M.L. Fontaine 1 , C. Denonville 1 , R. Strandbakke 2 , J.M. Serra 3 , D.R. Beeaff 4 , C. Vigen 4 and T. Norby 2 1 SINTEF Materials and Chemistry, 2 University of Oslo, 3 CSIC, 4 CoorsTek Membrane Sciences AS Why high temperature proton ceramic electrolysers? Processing and performance of early-stage single cells Up-scaling strategies for tubular proton ceramic electrolysers
High temperature electrolysis enables utilization of waste heat resources ΔH 2H 2 + O 2 2H 2 O PCE SOE
Key differences between SOE and PCE - advantages and challenges Solid Oxide Electrolysers Well proven technology U 4e - SOEC Scalable production High current densities at thermo-neutral voltage 2H 2 O Long term stability challenges 600-800°C Delamination of O 2 -electrode 2O 2- O 2 Oxidation and degradation of Ni-electrode with high steam contents 2H 2 High temperatures Proton Ceramic Electrolysers U 4e - PCEC Less mature technology 2H 2 O Fabrication and processing challenges Produces dry H 2 directly 2H 2 Potentially intermediate temperatures 4H + 400-700°C Slow O 2 -electrode kinetics O 2
High temperature electrolyser with novel proton ceramic tubular modules (2014-2017) Development of tubular a b O 2 c O 2 O 2 O 2 O 2 H 2 O H 2 O H 2 O e - e - e - e - e - e - cathode supported H + H + H + e - e - e - O 2 electrolyte cell O 2- H + H + H + BZY H + BZY H + BZY H + e - Conductor Protonic conductor Mixed Oxygen ion-electronic conductor nanoparticles Development and Single tube module optimization of anodes development and and current collection testing Multi-tube module testing Aim: 1kW demo Process integration and evaluation
Tubular half-cell production Wet milling of precursors Extrusion of BZCY-NiO support Spray- or dip-coating Dip-coating suspensions NiO based paste Solid State Reactive Sintering
100 microns 100 microns 100 microns BZY10 // BZCY72-NiO BZCY72 // BZCY72-NiO BZY10 // BZY10-NiO Dense electrolyte @ Porous electrolyte @ Dense electrolyte @ 1550 ° C – 24h 1550 ° C – 24h 1550 ° C – 24 h 1610 ° C – 6h 1610 ° C – 6h 1610 ° C – 6 h 1650 ° C – 6h 40 microns 40 microns 40 microns 1670 ° C – 6h
Development of new anode materials T ( ° C) Ba 1-x Gd 0.8 La 0.2+x Co 2 O 6- δ displays best PCE 800 600 400 2 100 O 2 -H 2 O-electrode performance (symmetrical disk samples) T ( ° C) 1 10 750 700 650 600 550 500 450 400 350 1.5 2 )) Log( R p,app ( Ω cm 2 ) R p,app ( Ω cm 0 1 1.0 2 ) 0.5 X = 0.1 log (( R p ( Ω cm X = 0.5 X = 0* 0.0 -1 0.1 GBCF / BZCY X = 0.3 BSCF / BCY -0.5 Pr 2 NiO 4 / BCY LSCF / BCY 0.04 Ω cm 2 BGCF / BCY -1.0 BGLC (x=0) / BZCY -2 0.01 BCZF -1.5 0.8 1.0 1.2 1.4 1.6 1.8 1.0 1.1 1.2 1.3 1.4 1.5 1.6 -1 ) -1 ) 1000/T (K 1000 / T (K
Anode processing on tubular cells Single segment, reduced at 1000°C for 24h in 5% H 2 Capped and sealed using custom-made glass ceramic (CoorsTek Membrane Sciencies) Steam electrode (BGLC785) drip-coated and brush-painted Fired in dual atmosphere with applied bias: - 2% O 2 outside, 5% H 2 inside - E cell = 1.4 V during firing (above 500°C) Electrolysis tests using gold as the current collector
Electrolysis tests of single cell p O 2 : 80 mbar 2.0 p H 2 O: 1.5 bar p H 2 : 300 mbar Potential (V) 1.5 700°C 650°C 600°C 550°C 1.0 0 50 100 150 200 250 -2 ) Current (mA cm
Improved performance with increasing steam content and current load Both electrolyte and electrode performance improved with increased steam content High ohmic resistance indicates current collection limitations 1.8 1.6 -1 p H 2 O: 0.5 bar Voltage (V) 1.4 0 2 ) // ( Ω cm p H 2 O: 1.5 bar 1 OCV 1.2 -2 11 mA cm Z -2 21 mA cm 2 -2 64 mA cm 1.0 3 0.8 4 5 6 7 8 0.00 0.05 0.10 0.15 0.20 0.25 / ( Ω cm 2 ) Z -2 ) Current density (mA cm
Electrode resistance an order of magnitude higher than expected values from button cell testing T ( ° C) 700 600 500 400 2 100 0.8 550 Tube segment 600 1.5 bar steam 0.6 600 (x =0.5) 1 10 650 2 )) 0.4 2 )) 700 Log(Rp ( Ω cm 2 ) log( R p ( Ω cm 2 ) 700 (x = 0.5) Rp ( Ω cm R p ( Ω cm 0.2 0 1 R P (x = 0) 0.0 1 R P modelled R P modelled (x = 0) -1 0.1 -0.2 R P (x = 0.3) Target: R P (x = 0.5) -0.4 0.2 Ω cm 2 -2 0.01 0 50 100 1.0 1.2 1.4 1.6 -2 ) -1 ) I (mA cm 1000/T (K Button cell wet air
Scaling up – segmented tubes to drive up the voltage
Scaling up – stacking individual segments
Scaling up – “Printing in series”
Segmented-in-series tubular cells Novel interconnects H 2 O+O 2 electrode (PCEC anode) with H 2 O + O 2 flow integrated and patterned external current collection Novel external current collectors at closed/open ends of tube Electrolyte H 2 electrode (PCEC cathode) Porous support 1 H 2 flow BZY10 (SSRS or oxide) BZCY72 or BZCY (SSRS) + 2 3 1 or BZCY72 (SSRS or BZY10 (SSRS or sintering aid + pore oxide) oxide) formers + NiO
Manufacturing process Clean room activities 20 cm Annealing of Production of tubes Dip-coating Powder Pastes tubes (hang- by extrusion and conditioning preparation of tubes firing) collars • Milling of SSRS • Drying in air (organic • Drying Hang-firing of cells precursors and based coating) or at • Cutting oxide powders 60°C for water based • Masking and coating • Drying suspensions • Sieving • Batching 3 cm Slurries preparation Green support coated with cathode (green) and electrolyte (white) layers • Water based slurry for SSRS mixtures • Organic based slurries for oxide mixtures Green supports with electrodes
Parameters investigated Support + Support + Supports fuel electrode + fuel electrode electrolyte Shrinkage; porosity Shrinkage, porosity Shrinkage, porosity Annealing Coated part Coated part • • • PF content Uncoated part Uncoated part • • • Sintering aid • Thickness of electrode Thickness of electrode Viscosity Viscosity • • Powder loading Powder loading • • Thickness and densification of electrolyte Oxide vs SSRS • Powder loading •
Broken section: several segments; non-optimized sintering NiO- NiO- BZCY NiO- BZCY Support Support BZC BZC electrolyte BZC electrolyte Y Y Y 100 µ m 100 µ m 50 µ m 50 µ m 50 µ m
Optimized processing parameters for multi-layer sintering 300 µ m Dense electrolyte Dense NiO-BZCY (porosity will be generated by NiO reduction to Ni) 30 µ m Porous BZCY support 23
Conclusions High temperature proton ceramic electrolysers can produce dry, pressurized hydrogen Processing and manufacturing of tubular half cells is now well established State-of-the-art electrolyser anodes are developed on button cell scale Deposition and firing protocols for tubular cells currently being developed Segmented-in-series tubular cells are needed to reduce total current of tubes in real operational conditions
Acknowledgements The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) for the Fuel Cells and Hydrogen Joint Technology Initiative under grant agreement n° 621244. Thank you for your attention!
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