S-TiO2/Ti as efficient and stable electrocatalysts electrode for decomposition of HI to produce hydrogen

Abstract The hydrogen iodide decomposition reaction of the sulfur-iodine (SI) cycle is realized by electrolysis at room temperature to achieve efficient hydrogen production, while iodine is recycled throughout the SI reaction. In this work, we report a facile hydrothermal method for the synthesis of sulfur-doped titanium dioxide (S- \(\hbox {TiO}_2\) ) nanosheets with evenly distributed on the Ti foil (S- \(\hbox {TiO}_2\) /Ti). The noble metal-free S- \(\hbox {TiO}_2\) /Ti electrode demonstrates excellent electrochemical catalytic performance for iodine evolution reaction. It can deliver a high current density of 100 mA/ \(\hbox {cm}^2\) with a potential of 1.05 V, which is close to 90% of that of precious metal platinum and 5.6 times of bare Ti foil. Furthermore, the S- \(\hbox {TiO}_2\) /Ti electrode is stable in a mixed acid solution of HI and \(\hbox {H}_2\hbox {SO}_4\) . Compared to \(\hbox {TiO}_2\) /Ti, diffuse reflectance spectroscopy and ultraviolet photoelectron spectroscopy analysis evidence a reduction in the band gap and work function of S- \(\hbox {TiO}_2\) /Ti due to the doping of sulfur. Correspondingly, the current efficiency approaches to 100% under the electrolysis constant voltage 1.30 V. Eventually, the detailed mechanism to describe the improvement of the electrocatalytic performance was suggested. Graphical abstract