Hydrogen Recovery from H₂S Electrochemical Oxidation: A DFT Study

Electrolysis of hydrogen sulfide (H2S) offers a green and zero-emission process for producing hydrogen and treating pervasive and harmful H2S from oil and gas refineries. However, the development of such a technology requires an efficient and stable catalyst. Herein, we investigate the mechanism of the electrochemical H2S oxidation reaction (H2SOR) over various metal oxides and metal sulfides using DFT calculations. We demonstrate why RuO2 has been widely reported as an active H2SOR catalyst. We also demonstrate that metal oxides are affected by sulfur poisoning and that their activity toward H2SOR is enhanced following sulfur coverage. By including surface coverage analysis for S-intermediates, we identify TiO2 as a promising and durable catalyst for H2SOR with a 0.49 V calculated overpotential. We also investigated the H2SOR activity of pristine and doped metal sulfides. We show that even though doping appears to reduce the overpotential needed to drive H2SOR, the S-intermediates block the active sites and decrease the reactivity. This research paves the way for the creation of more effective catalysts by providing a computational understanding of H2S electrolysis over various catalysts.