New scientometric study maps explosive growth in green hydrogen technology

As the world races toward carbon neutrality, a comprehensive new study published in ENGINEERING Energy (formerly Frontiers in Energy) provides the first systematic roadmap of research in solid oxide electrolysis cells (SOECs)—a breakthrough technology that could produce green hydrogen at costs competitive with fossil fuels. The scientometric analysis, led by researchers at Harbin Institute of Technology, Shenzhen, reveals that SOEC research has surged 400% since the Paris Agreement and identifies co-electrolysis of CO₂ and water as the field's fastest-growing frontier.

SOECs represent the most efficient pathway for converting renewable electricity into hydrogen or syngas, achieving electrical-to-hydrogen efficiencies below 40 kWh/kg—substantially better than conventional alkaline or PEM electrolyzers. This efficiency advantage could drive green hydrogen production costs under $2/kg, positioning it to replace gray hydrogen in industrial applications. However, the technology's rapid evolution has created a fragmented research landscape, making it difficult for scientists and policymakers to identify priorities and collaboration opportunities.

"Our analysis transforms 40 years of scattered research into a clear narrative," explains Dr. Zehua Pan, corresponding author from Harbin Institute of Technology. "We can now pinpoint exactly where the field is heading, who's leading the charge, and which innovations will define the next decade."

The Analysis

The research team analyzed 1,276 peer-reviewed articles from the Web of Science database spanning 1983-2023, employing advanced scientometric tools to map publication trends, international collaborations, and keyword networks. The study focused on six critical domains: fuel electrodes, air electrodes, electrolytes, CO₂-H₂O co-electrolysis, proton-conducting SOECs, and system modeling.

Key findings reveal how global climate agreements directly shaped research momentum. After the Kyoto Protocol's 2005 entry into force, publications began rising steadily. The 2015 Paris Agreement triggered an explosive growth phase that continues today, with annual output jumping from 74 papers in 2013 to 124 in 2019 and continuing to climb.

Global Leadership and Collaboration

China dominates the field with 508 publications—nearly triple the United States' 182—and leads in total citations (10,424). However, Denmark achieves the highest average citations per paper (61), reflecting its strength in high-impact innovations. The top five contributing nations are China, USA, Germany, Denmark, and Japan, forming distinct research clusters with strong intra-regional collaboration.

The most influential journals are International Journal of Hydrogen Energy (197 papers) and Journal of Power Sources (133 papers), while Journal of the Electrochemical Society commands the highest average citations per article (44.2), indicating its role in publishing breakthrough findings.

Research Frontiers and Materials Revolution

The analysis identifies two dominant emerging trends:

1. Co-electrolysis Dominance: Traditional steam electrolysis keywords like "hydrogen production" are being overtaken by "CO₂ electrolysis" and "co-electrolysis," reflecting a strategic shift toward converting carbon dioxide into valuable syngas, directly supporting carbon neutrality goals.
2. Proton-Conducting SOECs: This subfield, averaging publication year 2019, attracts the highest annual citations (13.83 per paper), making it the most dynamic research area. Proton-conducting ceramics operate at lower temperatures than conventional oxygen-ion conductors, promising faster startup, longer durability, and cheaper materials.

Electrode Innovation Breakthroughs

The study reveals critical challenges and solutions across SOEC components:

• Fuel Electrodes: Research focuses on overcoming Ni-YSZ electrode degradation through "in-situ exsolution"—a strategy where metallic nanoparticles spontaneously emerge from perovskite oxides during operation. This creates highly active, carbon-resistant catalysts that eliminate the need for protective hydrogen feeds.
• Air Electrodes: "Delamination" is the most pressing issue, with electrode layers separating from electrolytes under high current. Recent work emphasizes nickelate-based materials like Pr₂NiO₄ and barrier-layer engineering to enhance adhesion.
• Electrolytes: While yttria-stabilized zirconia (YSZ) remains standard, research is rapidly shifting to proton-conducting BaZrO₃-BaCeO₃ ceramics, with novel tri-doped compositions achieving unprecedented chemical stability and conductivity.

System-Level Maturation

The analysis shows research evolving from materials science to system integration. Modeling studies increasingly focus on economic analysis, cost reduction, and coupling SOECs with renewable energy sources and industrial processes like Fischer-Tropsch synthesis. Leading institutions are now optimizing entire "power-to-gas" plants rather than individual cells.

Strategic Implications

"This isn't just academic," says Dr. Yexin Zhou, co-corresponding author. "Our maps help funding agencies target investments, guide startups toward viable materials, and show policymakers which countries are building sustainable advantages in the hydrogen economy."

The study serves as a strategic blueprint for:

• Researchers seeking collaboration partners and underexplored niches
• Industry identifying commercial-ready technologies
• Governments tracking national competitiveness in clean energy innovation

Publication Details

The review article, "Scientometric analysis of research trends on solid oxide electrolysis cells for green hydrogen and syngas production," was published in ENGINEERING Energy (formerly Frontiers in Energy), 2024, Volume 18, Issue 5, Pages 583–611.

DOI: 10.1007/s11708-024-0945-5
Article Link: https://doi.org/10.1007/s11708-024-0945-5

This work was supported by multiple Chinese research foundations including the National Natural Science Foundation of China and the Science, Technology and Innovation Commission of Shenzhen Municipality.

Journal Citation:
Kang, S., Pan, Z., Guo, J., Zhou, Y., Wang, J., Fan, L., Zheng, C., Cha, S. W., & Zhong, Z. (2024). Scientometric analysis of research trends on solid oxide electrolysis cells for green hydrogen and syngas production. Frontiers in Energy, 18(5), 583–611. https://doi.org/10.1007/s11708-024-0945-5