The sulfur-iodine cycle is one of the most promising thermochemical cycles for hydrogen production. Its coupling with a solar energy primary source is a great challenge to achieve efficient and economically competitive H-2 production. Within this cycle, the decomposition of sulfuric acid plays a key role, with this process being the most energy-demanding reaction step. In this paper, a combined computational and experimental study of the decomposition at high temperature of H2SO4 to SO2 is presented. The scope of this paper is to present new information and data about the experimental high-temperature decomposition of sulfuric acid carried out in a solar reactor in view of a possible industrial exploitation of this reaction. Starting from a new complete thermodynamic modeling of the process, carried out by investigating the effect of the pressure and the temperature on the SO2 conversion rates, the study of the high-temperature decomposition of H2SO4 by direct solar radiation using a Fe2O3-based catalyst was carried out for the first time. The modeling and experimental results obtained are discussed together with the available literature. In summary, SO2 conversion yields close to thermodynamic predictions were obtained in the temperature range 1050-1200 K at a starting sulfuric acid partial pressure of p = 0.61 bar.