Tuning the ZnO-activated carbon interaction through nitrogen modification for enhancing the H₂S removal capacity

Herein, an unusual strategy is reported to enhance the H₂S uptake capacity by varying the ZnO-support interaction and controlling the acid-basic environment of the pore channel; this is in place of the generally reported method of decreasing ZnO nanoparticle size and optimizing their porosity. With this regard, coal based activated carbon (AC) is selected as the support and the interaction with ZnO is tuned by introducing N species on AC surface through a soft nitriding strategy. Our strategy is confirmed to be prospective based on the fact that the N-modifying AC supported ZnO adsorbent show a maximum breakthrough sulfur capacity (BSC) of 62.5 mg S/g sorbent, two times larger than that without N-modification (30.5 mg S/g sorbent). The enhanced BSC is attributed to the introduced N species, which not only increases the basicity of the water film condensed in the pores, promoting the dissociation of H₂S and H₂O, but also influences the electronic structure of ZnO, accelerating the rate of lattice diffusion during in sulfidation process. It is also found that the high BSC of sorbent with N modification is related to the doped N concentrations, ZnO dispersion and the material porosity. This paper provides a new insight for designing supported ZnO based adsorbents.