Prabhakar Singh, Boxun Hu, and Ugur Pasaogullari - University of ConnecticutJeff Stevenson, Pacific Northwest National Laboratory

November 14, 2017

Proton-Conducting Solid Oxide Electrolysis Cells for Large-Scale Hydrogen Production at Intermediate Temperatures

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Project Title: Proton-Conducting Solid Oxide Electrolysis Cells for Large-scale Hydrogen Production at Intermediate Temperatures University of Connecticut: Prabhakar Singh(PI); Boxun Hu and Ugur Pasaogullari (Co-PI)Pacific Northwest National Laboratory: Jeff Stevenson (Co-PI)

Project Vision: The overall objective of the proposed research program is to develop innovative, cost effective and efficient proton-conducting solid oxide electrolysis cells (H-SOECs) for large-scale hydrogen production at intermediate temperatures (600-800˚C).

HydroGEN Kick-Off Meeting

Project Impact: (a) achieve anoperating current density (>1 A/cm2) with theperformance degradation rate not to exceed theDOE performance metric (< 4 mV/1000 h),(b) demonstrate stable intermediate temperature(600-800oC) operation with low area specificresistance through bulk, interface and surfaceoptimizations, and(c) meet hydrogen production cost goal (< $2/kgH2) by the use of non-noble and non-strategic celland stack component materials.

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Innovation and Objectives

Project historyExtensive on going research with government agencies and industries towards the development of SOFC and SOEC systems. Background and experimental capabilities exist to advance H-SOEC.

Proposed targets

PartnershipsThe research team will work with PNNL in developing and testing H-SOEC. Team will heavily leverage EMN network. We will work with NREL, INL and LBNL for the optimization of materials.

BarriersTechnical barriers include development of electrolyte and electrode chemistry that remains amenable to long term stability, low temperature sintering and desired proton conductivity.

Metric State of the Art

Proposed

Conductivity ~10-3S/cm 10-2S/cm

Sinteringtemperature

>1450˚C <1350˚C

Thickness >25 micron ~15-20 micron

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Technology InnovationKey Innovations:(a) Computational materials design and optimization for chemically and structurally

stable ceramic electrodes and electrolyte(b) Synthesis and fabrication processes for tailoring active components with enhanced

catalytic sites and reduced area specific resistance(c) Mitigation of electrode delamination and chromium assisted poisoning(d) 3D multi physics modelling of proton-conducting SOEC stacks

Key Benefits: Development of cost effective and stable materials, processing

techniques and architectures for demonstrating and deployment of hydrogen production

Mechanistic understanding of materials sintering, performance degradation, and structure-performance relationships

Implementation of the getters; mitigation of electrode poisoning; BOP materials and heat treatment conditions

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Effective Leveraging of the EMN Resource NodesThe proposed H-SOEC program plans to extensively utilize USDOE-EMN nodes to accelerate the development and optimization of proton conducting electrolyte as well as electrodes that offer lower polarization losses and ease of fabrication to meet the cost and performance targets of large scale hydrogen production.

• Materials limitations and technology gaps have been identified. • Chemical and structural stability of materials in H2-H2O atmospheres• Processing and densification of electrolyte • Minimization of polarization losses at operating conditions• Long term stability to meet the established goal

• EMN capabilities will be utilized for the optimization of materials.• NREL: High-Throughput Experimental Thin Film Combinatorial Capabilities

(characterization) • Experts: Dr. Andriy Zakutayev, John Perkins, and David Ginley

• INL: Advanced Materials for Water Electrolysis at Elevated Temperatures, • Experts: Drs. Ting He and Dong Ding.

• LBNL: DFT and Ab Initio Calculations for Water Splitting Including Real-Time Time-Dependent Density Functional Theory,

• Expert: Dr. Lin-Wang Wang

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Milestone Summary Table Recipient Name: University of Connecticut, Prabhakar Singh

Project Title: Proton-Conducting Solid Oxide Electrolysis Cells for Large-scale Hydrogen Production at Intermediate Temperatures

Task Number

Task or Subtask Title

Milestone Type

Milestone Number*

Milestone Description

Milestone Verification

Process

Anticipated Quarter

1 Program

management and plan

Milestone M1-1 Program priorities established in consultation with program manager.

Verify and consult with program manager

1

2

Development of proton conducting

electrolyte and electrode materials

Milestone M 2-1

Candidate electrolyte and electrode material compositional space for H-SOECs are selected based on guidance from advanced modeling tools and analytical techniques.

Verification completed through report review.

1

3

Fabrication and electrochemical

performance evaluation of single-

cell SOEC

Milestone M3-1

First selected proton conducting electrolyte synthesized with a density of >90% and a proton conductivity of at least 0.01 S/cm at 700 oC

Verification completed through testing of SOECs.

2

4

Characterization of selected electrolyte

and electrode materials

Milestone M4-1

Selected H-SOEC electrolyte and electrode materials electrolysis performance is measured and is relatively stable (<10 mV/1000 h) for 50-hour test in real-world electrolyzer operating conditions.

Verification completed through testing of SOECs.

3

Go/No-Go Decision

point GNG-BP1

Developed proton-conducting electrolyte has a low sintering temperature (<1450°C) and a proton conductivity of at least 0.01 S.cm-1 at 650°C, a thickness of <25 µm, and a density of >90%. Developed electrolyte/electrode materials provides stable electrolysis performance and polarization for at least 50 hours showing initial performance of at least 1 A/cm2 at ≤1.4 V at a temperature of ≤700 oC

Test at least 2 SOECs to verify. 4

Project Tasks and Milestones

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Technology Gaps and Research Needs

• Chemical and structural instability-oxidizing and reducing atmospheres at IT• Processing and densification• High polarization losses• Poisoning due to extrinsic contaminants

Lower electrical conductivity, mixed conduction, 2nd phase formation at GB, hydration and carbonation, high polarization losses, limited electrocatalytic activity, Cr poisoning unknown

• Identify dopant type and level.• Optimize interface/ TPBA.• Identify oxygen electrode / support.• Demonstrate long term stability under system conditions.• Identify approaches for reducing VN.

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Advantages of the Proposed H-SOECs

• Low operating temperature (550-750˚C)• Possible pure pressurized hydrogen production• Cost reduction for hydrogen production

Attributes H+-SOECs O2-- SOEC Operating Temperature 550-750°C 650-850°CElectrolyte conductivity 0.01 S.cm-1 at 650°C 0.015 S.cm-1 at

850°C Products Pure H2 H2O +H2

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Scope of Work: The HTE combinatorial node at NREL will be responsible for synthesis of combinatorial libraries of Y-substituted BaZrO3 (BZY). Other minor additives (e.g. transition metals, alkali earth, rare-earth) that have a potential to improve BZY’s sinterability without inducing secondary phases or impeding protonic and electronic charger transport. The films will be characterized at NREL for composition, structure, morphology, and electrical properties at room temperature. These NREL thin film results will be compared to the UConn bulk synthesis results, in order to determine how thin film morphology and ceramic sinterability correlate with each other. At later phases of the project, optimized thin film compositions may be deposited at NREL on ceramic or metallic supports provided by UConn.

NREL: High-Throughput Combinatorial CapabilitiesHigh-Throughput Experimental Thin Film Combinatorial CapabilitiesExperts: Drs. Andriy Zakutayev, John Perkins, David Ginley

Technical discussion held with Dr. Andriy Zakutayev has identified scope of work for the development of electrolyte chemistry and validation through high temperature experiments.

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Advanced Materials for Water Electrolysis at Elevated Temperatures (Experts: Drs. Ting He and Dong Ding)

INL: Advanced Materials for Water Electrolysis

Technical discussion held with Drs. Ting He and Dong Ding has identified two tasks for the development of dense electrolyte and performance improvement of the anode.

Task 1: Development of electrolyte densification technique and determination of corresponding ionic conductivities (Q1-Q2) - This task will consist of the identification of dopants, powder synthesis and processing techniques that results in the development of dense electrolyte (>95-97%) supported on porous electrode support. Transition metal and lanthanide group dopants will be experimentally evaluated initially.Task 2: Anode microstructural modification for performance improvement (Q3-Q4): This task will consist of identification of infiltration techniques and microstructural modifications to reduce electrode polarization. Mechanisms for polarization losses in the cells will be developed

UConn will fabricate and electrically test fabricated cells. Long term degradation mechanisms will be proposed and validated

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Summary

• Literature search will be updated. Powder synthesis and cell fabrication techniques will be reviewed.

• Cells using doped BZY electrolyte will be fabricated and performance/ polarization will be analyzed. Mechanisms for polarization losses will be identified

• We will work closely with EMN to select electrolyte/ electrode formulations along with interface modifications.

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Thank YouDr. Prabhakar SinghUTC Chair Professor, Materials Science and EngineeringUniversity of Connecticut44 Weaver Road Unit 5233 Storrs, Ct 06269-5233Phone: (860) 486 8379Fax: (860) 486 8378Email: singh@engr.uconn.edu