In situ Bunsen reaction coupled with HI electrolysis for hydrogen production from sulfur-containing emissions

Studies on Conventional Bunsen reaction (SO 2 + I 2 + 2H 2 O → 2HI + H 2 SO 4 ) with molten iodine or low-temperature Bunsen reaction with iodine-solution for both Sulfur-Iodine (S-I) cycle and H 2 S splitting cycle for hydrogen production have encountered great challenges such as side reactions, acid products separations, corrosion to reactors, and excessive material handlings, just name a few. We found that the Bunsen reaction can proceed sustained when gas SO 2 is replaced by sulfite solutions. In this study, we couple the insistent Bunsen reaction with the HI electrolysis in its anodic chamber. Cyclic voltammetric (CV) and linear sweep voltammetric (LSV) analyses reveal the electrochemical-chemical (EC) coupling mechanism, the necessity of the fluid convection (in removing the formed iodine film on the electrode surface), and the possibility of modulating the process efficiency by changing the sulfite to HI ratio. Cycling stability tests demonstrate great stability over 80 cycles under stirred conditions, with >95% retention of initial electrochemical activity. This work offers a simplified electrochemical route for large-scale hydrogen production from sulfur-containing emissions when they have been converted into sulfite. • This work invented iodine-iodide redox loop in the anodic side of HI electrolysis to produce H 2 . • This invention introduces the Bunsen reaction to the anodic chamber to realize the 2I − ⇌ I 2 loop. • CV/LSV confirms EC coupling mechanism and convection-dependent I 2 film removal. • Sulfite-to-HI ratio governs reaction pathway, enabling process tunability. • This invention will potentially simplify the S-I cycle and H 2 S splitting cycle for H 2 production.