Electrospray Deposition of Catalyst Layers with Ultralow Pt Loading for Cost-Effective H₂ Production by SO₂ Electrolysis

The hybrid sulfur (HyS) thermochemical cycle has been considered as a promising approach for the massive production of clean hydrogen without CO₂ emissions. The key to advance this technology and to enhance the cycle efficiency is to improve the electrocatalytic oxidation of SO₂, which is the pivotal reaction within this process. Hence, this paper investigates, for the first time, the effect of electrospray and air gun deposition techniques and the influence of very low Pt loadings (<0.3 mg Pt/cm²) on catalyst durability and activity. The variation of electrochemical active surface area (ECSA) with the number of cycles demonstrates the significant impact of the electrode fabrication method and catalyst loading on the catalyst durability with considerable ECSA values for electrosprayed electrodes. Electrodes prepared with low platinum loadings (0.05 mg Pt/cm²) exhibit elevated catalyst activity and stability under sulfuric acid conditions and maintain a crucial current density after 5 h of electrolysis. This work extends the understanding of the SO₂-depolarized electrolysis (SDE) process and gives suggestions for further improvements in the catalyst layer fabrication, which provides potential support for the large-scale research and application of the HyS cycle.