Study of the synergistic mechanism for efficient calcium looping ethanol reforming for hydrogen production and in-situ CO2 conversion using CaO-based multi-functional materials

Carbon dioxide (CO 2 ) is the main byproduct formed when ethanol is reformed to produce hydrogen (H 2 ), which causes a decrease in H 2 purity and yield and an increase in separation costs. Herein, we report a novel technology of ethanol reforming for hydrogen production coupled with in-situ CO 2 conversion (ER-CO 2 ). This process that achieves integrated H 2 generation and CO 2 management using multi-functional materials (MFM) based on CaO and doped with non-precious metals (Ni, Co, Fe, Cr, Mo). The experiment and characterization results combined with DFT (Density Functional Theory) calculations showed that Ni doping decreased the oxygen vacancy formation energy and enhanced CO 2 adsorption. In the prepared MFMs, Ca-Ni-5 MFM exhibited excellent overall performance with ethanol conversion of 95.51%, H 2 purity of 94.37%, CO 2 conversion of 90.26% and H 2 /CO ratio of 1.69:1. However, after ten cycles, the Ca-Ni-5 MFM performance declined due to the covered of Ni by CaCO 3 /CaO layers, which resulted from progressive sintering and repeated lattice expansion, ultimately leading to the deactivation of the MFMs. This in-depth investigation into the reaction and deactivation mechanisms provides critical insights and a solid theoretical foundation for the rational design of highly stable MFMs in future applications.