5. Conclusions
The simultaneous incorporation of AuNPs during the synthesis of zinc hydroxide/GO composite results in a very efficient H2S adsorbent. On its surface, besides hydrogen sulfide various sulfide oxidation products are deposited including elemental sulfur, sulfite and sulfates. Addition of AuNPs causes an increase in surface heterogeneity resulting in abundance of active terminal groups available for initial adsorption of H2S. Then, as a result of the combined action of zinc hydroxide photoactivity, specific features of the graphene phase and enhancement in electron transfer and oxygen activation by AuNP, the oxidation of adsorbed hydrogen sulfide takes place. The role of graphene phase is in: (1) increasing the surface structural and chemical heterogeneity, (2) participation in oxygen activation and formation of superoxide ions, (3) separation of holes from electron preventing their fast recombination, (4) increasing the efficiency of an electron transfer. For that last process AuNPs have also a significant contribution. Since zinc oxide is commonly used as an adsorbent for H2S removal at high temperatures, as the main and visible light active component of our composites it should not be costly. Graphite oxide can be considered as expensive nowadays, but the advancement in graphene science is expected to lower its price. The cost of AuNP will be always high, but maybe other non-noble metal NPs would be able to replace their function in the composites.
5. Conclusions
The simultaneous incorporation of AuNPs during the synthesis of zinc hydroxide/GO composite results in a very efficient H2S adsorbent. On its surface, besides hydrogen sulfide various sulfide oxidation products are deposited including elemental sulfur, sulfite and sulfates. Addition of AuNPs causes an increase in surface heterogeneity resulting in abundance of active terminal groups available for initial adsorption of H2S. Then, as a result of the combined action of zinc hydroxide photoactivity, specific features of the graphene phase and enhancement in electron transfer and oxygen activation by AuNP, the oxidation of adsorbed hydrogen sulfide takes place. The role of graphene phase is in: (1) increasing the surface structural and chemical heterogeneity, (2) participation in oxygen activation and formation of superoxide ions, (3) separation of holes from electron preventing their fast recombination, (4) increasing the efficiency of an electron transfer. For that last process AuNPs have also a significant contribution. Since zinc oxide is commonly used as an adsorbent for H2S removal at high temperatures, as the main and visible light active component of our composites it should not be costly. Graphite oxide can be considered as expensive nowadays, but the advancement in graphene science is expected to lower its price. The cost of AuNP will be always high, but maybe other non-noble metal NPs would be able to replace their function in the composites.
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