Natural andesite as a low-cost, sustainable bifunctional electrocatalyst for water splitting: Mechanistic insights into OER and HER
Geoenergy Science and Engineering, cilt.266, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 266
- Basım Tarihi: 2026
- Doi Numarası: 10.1016/j.geoen.2026.214655
- Dergi Adı: Geoenergy Science and Engineering
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Chemical Abstracts Core, Compendex, Geobase, INSPEC
- Anahtar Kelimeler: Andesite, Bifunctional electrocatalyst, Green hydrogen, Hydrogen evolution reaction, Oxygen evolution reaction, Raw geological material, Water splitting
- Eskişehir Osmangazi Üniversitesi Adresli: Evet
Özet
This investigation explores unrefined natural andesite as an economically sustainable, nearly cost-free bifunctional electrocatalyst suitable for comprehensive water splitting in alkaline environments, specifically 1 M KOH. By omitting complex and resource-intensive chemical synthesis procedures, this unprocessed geological mineral demonstrates competitive fundamental performance for both the Oxygen Evolution Reaction (OER) and Hydrogen Evolution Reaction (HER), with measured Tafel slopes of 77.22 and 90.71 mV dec−1, respectively. To assess intrinsic catalytic activity, an extensive Turnover Frequency (TOF) analysis was conducted, revealing conservative lower limits of 0.01984 s−1 for HER and 0.00990 s−1 for OER. These findings are supported by detailed Electrochemical Impedance Spectroscopy (EIS) measurements fitted with a Constant Phase Element (χ2 ≈ 10−3, Rct = 46.81 Ω for HER), which confirm significantly high intrinsic per-site activity, notwithstanding the bulk silicate matrix's concealment of numerous active sites. Furthermore, the catalyst exhibits robust operational stability and favorable performance when compared with other naturally occurring minerals such as molybdenite and pyrite. On a mechanistic level, we propose a plausible Fenton-like pathway involving mixed-valence iron centers in conjunction with dynamic surface reconstruction for OER, and a synergistic dual-site Volmer-Tafel/Heyrovsky process for HER. Ultimately, this study underscores andesite as a highly promising baseline geo-catalyst, demonstrating that its trace-metal centers are highly reactive. This establishes a strong foundation for future investigations into targeted nanostructuring and selective etching methods to unlock the full potential of earth-abundant rocks for scalable green hydrogen production.