Reaction, Interaction, and Product Regulation of Thermolysis Section of Cu–Cl Thermochemical Cycle System for Hydrogen Production

The four-step Cu–Cl thermochemical hydrogen production cycle can effectively convert heat energy into hydrogen energy, and the thermolysis reaction is the key stage for connecting the upstream and downstream reactions. This study focused on the influence of different upstream hydrolysates (Cu2OCl2 or CuO) on thermolysis and the different reaction mechanisms. The micromorphological changes during the reaction process, the specific information on the precipitated gases, and the effect of temperature and reaction time on the main and byproducts were analyzed. The results showed that the maximum CuCl yields of 84.58 and 82.26% were obtained from the thermolysis of Cu2OCl2 and CuCl2–CuO equimolar mixtures. During the reaction, both reaction feedstocks shrink and then melt and start to precipitate O2 at 430 and 415 °C, respectively. For the thermolysis of CuCl2–CuO mixtures, an excess of CuCl2 contributes to the main reaction. Finally, the complex reaction mechanism of thermolysis and product regulation was revealed.