Post-treatment of carbon by interparticle spillover hydrogen for sustainable adsorption of volatile organic compounds under humid conditions

Abstract

Porous carbons have attracted much attention as adsorbents for the removal of volatile organic compounds (VOCs), but they suffer from a significant loss in adsorption capacity when exposed to humid conditions. In this study, zeolite templated carbons (ZTCs) are post-treated with O2, H2, and spillover hydrogen. This process generates varying amounts and types of oxygen-containing functional groups (OFGs) at the carbon surface while maintaining the initial textural properties. Results from Boehm titration and FT-IR reveal that spillover hydrogen not only removes the OFGs in carbon more effectively, but also facilitates the reduction of O–C = O groups (i.e., Lactonic and Carboxyl groups) into Phenolic species. The dynamic adsorption behavior of the series of post-treated ZTCs for benzene is investigated under both dry and humid conditions (relative humidity = 80 %). The results indicate that ZTC treated with spillover hydrogen exhibits noticeable resistance to H2O poisoning in benzene adsorption, while the other three ZTC show similar behaviors. Furthermore, there is a scaling relationship between the fractions of Phenolic groups among OFGs and benzene uptake under humid conditions. It is believed that the types of OFGs on carbon surfaces are a critical consideration when designing VOC adsorbents for their use under humid conditions.