FeOOH has been explored as a promising adsorbent for low-temperature H2S adsorption. However, the nature of the active sites toward the desulfurization has remained elusive. Here, a series of gamma-FeOOH is prepared with well-defined lath-like and rod-like shapes by adjusting the pH value of the reaction system. The two shapes of gamma-FeOOH have identical bulk structures but expose different distributions of surface OH groups, namely singly ( FeOH, -OH), doubly ( Fe2OH, mu-OH), and triply coordinated ( Fe3OH, mu(3)-OH) hydroxyls, allowing us to investigate the geometrical-site-dependent desulfurization activity of gamma-FeOOH at molecular-scale level. Following a thorough analysis by X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and in situ Fourier transform infrared spectroscopy (In situ FT-IR), we demonstrate that singly hydroxyl ( FeOH, -OH) site is responsible for H2S adsorption, which acts as the active site for low-temperature desulfurization. (C) 2017 Elsevier B.V. All rights reserved.