Tunable N-doped ultra-microporous activated carbons: enhancing O2 activation to facilitate the conversion of H2S to H2SO4 at ambient temperature†

Abstract

The impact of activated carbon's pore size, particularly ultra-micropores, on the composition of catalytic oxidation products from hydrogen sulfide (H₂S) has been noted in the literature. Despite this, a comprehensive understanding of the process remains elusive. In this study, we fine-tuned the pore structure by modulating the activation temperature of carbon dioxide (CO₂), resulting in the synthesis of nitrogen-doped carbon materials characterized by a substantial fraction of ultra-micropores. These materials demonstrated remarkable selectivity for the production of H₂SO₄, with selectivity values ranging from 12.86% to 50.44%, markedly surpassing the outcomes reported in existing research. Further in-depth analysis revealed a pronounced positive correlation between the selectivity for H₂SO₄ and the prevalence of ultra-micropores. Additionally, findings from electron paramagnetic resonance (EPR) and in situ Raman spectroscopy have shown that ultra-micropores can effectively activate molecular oxygen (O₂), thereby promoting the conversion of H₂S into H₂SO₄. This research introduces a novel approach for the development of desulfurization catalysts that exhibit heightened selectivity for H₂SO₄ under ambient conditions, representing a significant advancement in the field.