Solid Oxide Fuel Cell (SOFC)
Solid Oxide Fuel Cells (SOFCs) are a nascent technology characterised by their utilisation of a solid oxide electrolyte to facilitate electrochemical conversion of hydrogen into electricity. Hydrogen fuel is fed into the anode, where it oxidises to release electrons and produce water as a byproduct. These electrons travel through an external circuit, producing an electric current, to the cathode, where oxygen or air is supplied. Oxygen is reduced at the cathode, producing oxide ions. The solid oxide electrolyte facilitates the free movement of these oxide ions between the anode and the cathode. Figure X illustrates the schematic of the SOFC technology. If the hydrogen fuel supplied to the SOFC is produced from renewable energy sources, SOFCs convert the chemical energy of hydrogen into electricity with zero emissions, making them an efficient source of clean energy.
SOFCs offer various advantages over other fuel cells, such as fuel flexibility, meaning that they can utilise hydrogen derivatives as fuel alongside pure hydrogen. They are also highly efficient, providing high electrical efficiency and due to their high temperature operation, they can be integrated with other industrial processes to utilise the waste heat and increase system energy efficiency.
Although still in its infancy, the SOFC market size is currently valued at £1.63B and poised for a significant market size growth projection of £11.95B by 2032. This projection comes at the back of stringent environmental policies, governments promoting fuel cell vehicles, and continuous technological advancements which have boosted investor confidence and allowed stakeholders to begin pilot projects. SOFC applications are plentiful, from large-scale stationary power generation to small-scale residential units perfect for combined heating and power applications. Yet, as with every technology in its infancy stage, SOFC are hindered by critical challenges that need addressing before it can take over the global fuel cell market. The biggest of these challenges is the durability and longevity of SOFC stacks. When paired with high capital costs, these challenges make SOFC an undesirable investment for stakeholders looking for short payback periods and low operational costs. Another challenge that needs addressing is the start/stop duration of SOFCs, as the system take a significant amount of time to heat up and, therefore, makes it unsuitable for dynamic applications.
Challenges Revealed Through Literature Review
Anode
- Maintaining high ionic conductivity
- Suffers from metal dusting
- Sulphur poisoning
- Deposition of carbon
- High resistance and overpotential
- High costs and characteristic property of evaporating above 1200°C to produce volatile species like RuO4
Cathode
- Degree of distortion increases with decrement in size
- Suffers from metal dusting, sulphur poisoning, deposition of carbon
- Higher order of catalytic activity towards O2 reduction reaction but at lower temperatures
- A decreasing trend in cell ohmic contribution as a function of increasing cathode overpotentials (Cobalt based cathodic systems). This behaviour is typical of ionic-electronic mixed transport characteristic reflecting the range of electrochemical reaction from triple phase boundary to surface of the electrode.
Electrolyte
- Doubly-doped ceria based electrolytic systems
- ScSZ has conductivity lower or equal than YSZ below 500°C of temperature of operation due to tendency of increment in activation energy for conduction with reducing temperature; for higher mol% of scandia, typically >8%, the cubic phase starts transforming to rhombohedral phase at lower temperatures, which has lower conductivities
- YSZ-LSM form pyrochlore with x ≤ 0.2 (La2Zr2O7), perovskite with 0.3 ≤ x ≤ 0.4 (SrZrO3) or both of them simultaneously at x ≥ 0.5, where x is strontium content. Formation of La2Zr2O7 has been confirmed at 900°C during SOFC operation, which reportedly affects cell operation negatively since the conductivity is lowered
- Electrical conduction under low O2 partial pressures
- LSGM reacts with cathodes in a manner whereby interdiffusion is the chief mechanism rather than formation of a different phase
Interconnector
- Addressing mechanical strength issues
- Preventing degradation issues such as coking, cracks, and delamination
- Handling chemical interaction with reductive/oxidative gas atmospheres and electrode materials
- Improved reliability & robustness
- Reduced degradation and cost
- Cell farbrication & testinf
- Cell/Stack integration & scale-up
- Stack/BOP integration & testing
- Lower cost and higher performance
Solid Oxide Fuel Cell (SOFC) – Academic Capability Mapping
Word cloud
The word-cloud of the primary and secondary keywords is presented for the Solid Oxide Fuel Cell (SOFC) technology. These keywords were used as the input to Scopus for the purpose of the Academic Capability Mapping. The analysis underscores key research areas like electrocatalysis and catalysts such as Perovskite.
Documents by Country
The number of papers published worldwide pertaining to Solid Oxide Fuel Cell (SOFC) since the year 2000, divided into three decades. Only the top 10 countries are displayed. The UK is number 6 in SOFC research globally. While not in the top 5, the UK seems to have a strong research capability in the field of SOFC. Enhancing this capability through additional research funding may help in reducing costs and streamline commercialisation.
Documents by Author (2000 – 2025)
Prominent UK academics and their affiliation is showcased. The y-axis represents the H-index of the authors, while the x-axis illustrates the number of papers published. It can be clearly seen that a majority of the UK’s top researchers are competitive against global researchers in the field of SOFC.
Documents by Affiliation
The number of papers published by affiliation in the UK since the year 2000 are showcased. Imperial College London leads the way with the most publications, closely followed by the University of Saint Andrews. The figure specifically highlights the top 10 UK institutions in the field of Solid Oxide Fuel Cells, providing a definite ranking list of universities with excellent expertise in the SOFC technology.
Solid Oxide Fuel Cell (SOFC) – Delphi Survey Analysis
Participant Identifiers
Industry Collaboration
Confidence Level
Country Affiliation
Key Performance Indicators
Key technical target predictions were provided by the participants, expected to be achieved by 2030.
Challenges
The participants were provided with several options and were asked to rank these options from 0 (least critical) to 6 (most critical). They were also provided with a text option to suggest additional challenges.
Additional Cathode Side Challenges
- Barrier layer free cathode
- Chromium tolerance
- Thermal expansion mismatch
- Degradation
- Delamination
- Corrosion
- Limit use of critical elements
Additional Anode Side Challenges
- Particle size and pores
- Contaminant tolerance
- Reversible operation ability
- Redox tolerance
- Improve microstructure
- Ni coarsening and migration resistant anodes
- Spatial distribution of the TPBs
Additional Stack and System Challenges
- Lifetime
- Stack degradation
- System start-up procedures
- Highly compact stack
- Sealing mechanisms
- Hydrogen recycling
- Flow and heat management
Solid Oxide Fuel Cell System Integration
- Balance the intermittency of renewable electricity
- Peak shaving of the electricity grid by operating SOFC at full capacity
- Grid backup and resilience in case of outage
- Microgrid construction and emergency power response
- Combined heat and power for residential applications
- Waste-to-Energy applications
- Industrial waste heat reutilisation for steam generation
- Coalbed methane integration
- Fuel supply systems
- Gas cleaning and conditioning equipment
- Methane (biogas) infrastructure may prove useful to provide alternative fuel sources
- Electrolysers may interact in case of direct fuelling
- Heat distribution systems
- DC-AC Adaptor
- Building Energy Management Systems (BEMS)
- Energy storage systems