In the Cux-Zn(1-x)O/SiO2 sorbents for ultradeep adsorptive removal of H2S from gaseous fuel reformates for fuel cells at room temperature, Cu promoter sites significantly increase sulfur uptake capacity of the sorbents. We report characterization of the family of Cux-Zn(1-x)O/SiO2 sorbents for reactive adsorption of H2S using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis, electron spin resonance (ESR), ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy (DRS) and calculations by the density functional theory (DFT). Both the supported ZnO phase and Cu promoter sites in the Cux-Zn(1-x)O/SiO2 sorbents are nano-dispersed, as shown by XRD. The Cux-Zn(1-x)O/SiO2 sorbents contain Cu promoter as the Cu2+ site of octahedral geometry, as found by the complementary ESR and UV–vis DRS. Mechanism of the promoter effect of the Cu2+ site in the Cux-Zn(1-x)O/SiO2 sorbents in reaction with H2S is proposed based on DFT calculations. Copyright © 2012 John Wiley & Sons, Ltd.