Fig. 2: ATR-FTIR spectrum and enlarged regions of interest of magnetite following hydrothermal reaction at 90 °C and 16 bar total pressure for 16 h compared to the controls.

(a) Magnetite with H2 and HCO3−. (b) Control sample using magnetite with H2 (c) Control sample using quartz with H2 and HCO3− (d) Control sample using quartz with H2. A A representative of three ATR-FTIR replicate spectra annotated with candidate functional groups. B Enlarged 3150 cm−1 to 3000 cm−1 region showing carbon-hydrogen bonding, and (C) Enlarged 2000 cm−1–1600 cm−1 region showing carbon-oxygen bonding, the identified peaks are annotated and highlighted by the shaded areas.