Hydrolysis of CuCl2 is the water splitting step of the Cu-Cl thermochemical cycle, where CuCl2 reacts with steam to produce Cu2OCl2 and HCI. In the present work, this gas-solid reaction was investigated to understand the mechanism and kinetics. Experiments were conducted in a semibatch fluidized bed reactor to study the effect of temperature (275-375 degrees C), steam mole fraction (0.4-0.9), and reaction time (0-3 h). The challenges due to the hygroscopic nature of the reactant, product agglomeration, and multiple side reactions to achieve smooth and consistent reactor performance were overcome by the addition of inert additives during fluidization. The analysis of the mechanism showed that the desired product Cu2OCl2 is formed initially and further undergoes decomposition to CuO and CuCl2. Also, with increasing temperatures, the yield of Cu2OCl2 decreases because of the formation of CuCl from reactant decomposition. The results indicate that a minimum steam mole fraction of 0.5 is required to prevent the formation of side product CuCl in the temperature range of 300-325 degrees C. The minimum steam requirement for maximum yield to Cu2OCl2 was found to increase with increase in temperature.