Zinc (hydr)oxide/graphite oxide/AuNPs composites: Role of surface features in H2S reactive adsorption

• In situ precipitation is a suitable method to introduce AuNPs to Zn/GO composites.
• H2S adsorption on AuNPs/ZnOH/GO increased 135% compared to that on Zn(OH)2.
• AuNPs activate oxygen promoting H2S oxidation into sulfur and oxysulfur salts.
• AuNPs delays recombination of e–h formed as a result of Zn(OH)2 photoactivity.

Zinc hydroxide/graphite oxide/AuNPs composites with various levels of complexity were synthesized using an in situ precipitation method. Then they were used as H2S adsorbents in visible light. The materials’ surfaces were characterized before and after H2S adsorption by various physical and chemical methods (XRD, FTIR, thermal analysis, potentiometric titration, adsorption of nitrogen and SEM/EDX). Significant differences in surface features and synergistic effects were found depending on the materials’ composition. Addition of graphite oxide and the deposition of gold nanoparticles resulted in a marked increase in the adsorption capacity in comparison with that on the zinc hydroxide and zinc hydroxide/AuNP. Addition of AuNPs to zinc hydroxide led to a crystalline ZnO/AuNP composite while the zinc hydroxide/graphite oxide/AuNP composite was amorphous. The ZnOH/GO/AuNPs composite exhibited the greatest H2S adsorption capacity due to the increased number of OH terminal groups and the conductive properties of GO that facilitated the electron transfer and consequently the formation of superoxide ions promoting oxidation of hydrogen sulfide. AuNPs present in the composite increased the conductivity, helped with electron transfer to oxygen, and prevented the fast recombination of the electrons and holes.

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