Carbon-Rich carbon nitride nanocatalysts for H2S selective oxidation

Abstract

Selective catalytic oxidation (SCO) of hydrogen sulfide (H2S) to sulfur exhibits significant advantages for H2S removal, including high efficiency, mild operating conditions and thermodynamic unlimitation for H2S removal. Recently, polymeric carbon nitride (PCN) has emerged as a candidate for H2S selective oxidation reactions, benefiting from its aromatic C-N hybridized π-conjugated system for H2S adsorption/dissociation and good sulfur tolerance. However, its performance is greatly hampered by the lack of sufficient surface active sites for O2 adsorption and activation. Herein, we demonstrate that the incorporation of carbon atoms in PCN matrix to constructure carbon-rich carbon nitride nanosheets is a facile strategy to advance the desulfurization performance. The carbon atoms uniformly incorporated in PCN backbones can effectively extend the aromatic π-conjugated electronic system and create abundant oxygen-containing functional groups on the surface. The improved electronic configurations and surface properties are beneficial for the adsorption and activation of H2S and O2. In addition, the nanosheet morphology favors for increasing the surface area of the material, thereby promoting the mass transfer of H2S and O2 during the desulfurization process. The optimized carbon-rich carbon nitride nanosheets exhibit a H2S conversion of 99% and a S selectivity up to 95% for H2S selective oxidation at 200 °C, and the reaction is not restricted by mass transportation and heat transfer at such a high conversion rate. This synthetic strategy allows ample choice of low-cost and easy-available organic precursors for the large-scale production of the desulfurization catalysts.