Water adsorption on carbon surface drives interfacial charge transfer and hydrogen radical generation

Water adsorption on carbon surface is common in humid environments and plays a significant role in interfacial redox processes. We report that water adsorption on hydrophobic carbon surface can lead to interfacial charge transfer. Under ambient air conditions, the adsorption of water facilitates the formation of hydrogen radicals and promotes interfacial reactions such as nitrate reduction. The ¹H solid-state nuclear magnetic resonance spectra and Raman spectra of hydrophobic carbon surface indicate that the initial stage of moisture adsorption is characterized by the formation of hydrogen bond network, followed by the adsorption of water molecules. Concurrently, it is observed that the concentration of reduction products on the carbon surface first increases and then stabilizes. We propose that the formation of hydrogen radicals and the progress of interfacial reduction reaction are related to the evolution of hydrogen bond network during water absorption. Using mass spectrometric detection of H₂¹⁸O in the product during water adsorption, a possible adsorption water favored interfacial reduction pathway was proposed. This research deepens the understanding of relationship between water adsorption and interfacial reactions, providing new insights into observed reduction reaction on surface of fine particles in the atmosphere.