Unraveling the role of CH3S* intermediates for efficient methane and hydrogen sulfide reforming over Mo/Al2O3 catalysts

The catalytic methane(CH 4 ) and hydrogen sulfide(H 2 S) reforming (H 2 SMR) represents a promising approach for producing high-value sulfur-carbon compounds and hydrogen without generating the greenhouse gas of CO 2 . Despite its significant potential, the mechanistic understanding of interactions between CH 4 and H 2 S remains contentious, posing substantial challenges for catalyst development. In this study, we employed a Mo/Al 2 O 3 catalyst to elucidate synergistic conversion pathways between CH 4 and H 2 S during H 2 SMR. At 1173 K with a reaction duration of 0.5 h, conversion rates of CH 4 and H 2 S reached 63.7 % and 59.2 %, respectively, accompanied by H 2 and CS 2 production rates of 688.8 μmol g −1  min −1 and 444.3 μmol g −1  min −1 , respectively. Notably, the catalyst exhibited stable performance over 5 h without significant deactivation, in contrast to pure methane cracking reactions where CH 4 conversion rapidly declined from 43.6 % to 14.3 %. Through in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) combined with alternating CH 4 /H 2 S exposure experiments, we successfully tracked the synergistic conversion pathway on the Mo/Al 2 O 3 catalyst. These investigations revealed that the formation of CH 3 S intermediates serves as a critical step facilitating CS 2 generation. This mechanistic insight not only advances fundamental understanding of H 2 SMR reaction pathways but also provides a rational foundation for designing optimized catalysts with enhanced stability and extended operational lifetimes. The identification of this intermediate-driven mechanism addresses previous controversies regarding CH 4 -H 2 S interactions and offers strategic guidance for developing efficient sulfur-resistant catalytic systems.