Synergistic decomposition of H2S into H-2 by Ni3S2 over ZrO2 support via a sulfur looping scheme with CO2 enabled carrier regeneration

Commercially viable H-2 production from H2S demands a well-designed and efficient technology concept with superior H-2 yield. We propose a novel sulfur looping scheme that involves carrier sulfidation and CO2 enabled carrier regeneration to simultaneously utilize H2S and CO2, the two common industrial waste gases, for valuable H-2 production. Using Ni3S2 as the active component, a high-performance sulfur carrier design is developed, where the selection of support is key. ZrO2 and MgAl2O4 supports were tested and both substantially improve the recyclability over cycles by imparting structural stability to Ni3S2. ZrO2 dramatically enhances the carrier performance, exhibiting a maximum increase of similar to 100% in sulfur uptake during the redox cycles compared to MgAl2O4. Furthermore, in fixed bed experiments at a high GHSV of 5000 hr(-1), ZrO2 supported carrier maintained its superior performance over MgAl2O4 with a similar to 9.5% higher total H2S consumption. Density functional theory calculations were performed to unveil the role of supports. ZrO2 is identified as a support with bifunctional characteristics that not only improves textural properties of the carrier, but also catalytically decomposes H2S and induces a synergistic dynamic with Ni3S2. On the other hand, MgAl2O4 acts only as a conventional inert support for morphology modifications with negligible interaction with H2S. This work demonstrates a novel strategy for H2S and CO2 utilization and provides new insights into effective support selection aiding the design of a robust and efficient sulfur carrier.