Advancing solid oxide electrolysis cells for green hydrogen production: A comprehensive techno-economic and materials-centric assessment towards decarbonized energy systems

Solid oxide electrolysis cells (SOECs) are emerging as high-efficiency platforms for green H₂ and CO-rich syngas, enabled by high-temperature operation (600–900 °C), advanced oxygen-ion electrolytes (e.g., doped ceria, ScSZ, LSGM), and mixed ionic–electronic conductor (MIEC) electrodes. Recent single-cell advances deliver current densities from 0.5 to 5.73 A cm⁻² at the thermoneutral voltage (VTN; ≈1.286 V at 800 °C), with H₂ production rates up to 2.10 L h⁻¹ cm⁻² and near-100% Faradaic efficiency in steam electrolysis. Proton-conducting designs (e.g., BZCYYb) reach 1.0–2.3 A cm⁻² at 600 °C, indicating credible pathways to lower-temperature operation. Durability has improved markedly: representative planar fuel-electrode-supported stacks show < 4%/kh degradation, and an electrolyte-supported stack sustained 23,060 h at 0.57%/kh. System-level demonstrations report 60–84% LHV AC efficiency at 10–225 kW, with best-case small systems achieving up to 91–93% (HHV/LHV) when strongly heat-integrated. Co-electrolysis (H₂O/CO₂) provides tunable H₂/CO for downstream synthesis, while pressurized operation reduces balance-of-plant penalties by delivering H₂ at elevated pressure. Techno-economic assessments indicate competitive H₂ costs when cheap renewable electricity is available: studies span ≈ €1.2–$5.9 kg⁻¹ , with large, well-integrated plants modeled at ≈ $2.6–3.2 kg⁻¹ for $17–30 MWh⁻¹ power. Key remaining gaps are mitigation of oxygen-electrode delamination at high current, redox/steam corrosion at the fuel electrode, and sealing/contact resistance in scaled stacks. We synthesize a materials-to-systems roadmap that prioritizes MIEC oxygen electrodes, robust metal/interconnect coatings, lower-T electrolytes, uniform thermal/fluid management, and pressurized, heat-integrated architectures to jointly maximize efficiency, reliability (≤1%/kh), and cost (>2 × manufacturing yield, >10,000 h stack life) for commercialization of SOEC-based hydrogen and e-fuels. • High-T SOECs achieve 0.5–5.73 A cm⁻² and near-100% Faradaic efficiency. • Durability rising: < 4%/kh degradation; stacks run > 23,000 h reliably. • System efficiency reaches 60–93% with strong heat-integration. • Co-electrolysis enables tunable H₂/CO for synthesis pathways. • Key gaps: electrode delamination, corrosion, and sealing resistance.