Mechanism of hysteresis for composite multi-halide and its superior performance for low grade energy recovery.

Sorption hysteresis commonly exists for different sorbents and has a great impact on the performance, and recently it was found that the multi-halide sorbents could reduce the hysteresis phenomena. Here we report the mechanism of the sorption hysteresis for multi-halide under equilibrium/non-equilibrium conditions and its superior performance for low grade energy recovery. We find that the inner reaction among different halides does not happen and contribute to sorption hysteresis in sorption/desorption phases under equilibrium conditions. While under non-equilibrium conditions, multi-halide sorbents reduce the hysteresis significantly (the average hysteresis temperature difference decreases from 23.4 °C to 7.8 °C at 4.41 bar). The phenomena is studied, and results show that the continuous reaction within different halides under heterothermic condition leads to an operable multi-stage reaction property, which corresponds to better flexibility and faster response to heat source. The utilization of solar energy as heat source for a cloudy day is analyzed, and multi-halide sorbent has much larger average refrigeration power (improved by 43%) and could work efficiently most of the time. Such characteristics are also prospective for other thermochemical reaction technologies, such as de-NOx and energy storage because of lower energy input and higher energy output features.