Efficient integration of calcium looping with methane bi-reforming using Pd-enhanced Ni-CaO dual functional nanomaterials

Integration technology of methane bi-reforming (BRM; a combination of methane steam and dry reforming) with calcium looping (CaL-BRM) offered a novel solution to reduce CO₂ emission, enabling direct capture and conversion of low-concentration CO₂ from sources into value-added products (H₂, syngas) within the same reactor. In this study, Ni-CaO-based dual-functional material (DFM), with a small quantity of palladium in the nanostructure, was developed via a continuous two-stage aerosol process and employed in the CaL-BRM. Experimental results demonstrate that Pd-Ni-CaO exhibited high activity and cyclic stability over multiple cycles, maintaining effective CO₂ capture (12.0 mmol_CO2/g_CaO) and BRM performance (>98 % CO₂ conversion; H₂/CO = 2) at a relatively low temperature (600 °C). Density functional theory calculations reveal that the presence of Pd lowered the activation energy of CH* dissociation, the rate-determining step, from 1.14 to 0.67 eV. The higher adsorption energy (−0.87 eV) of H₂O on the Ni-Pd surface and the lower energy barrier (0.62 eV) for subsequent dissociation contributed to the promising catalytic performance in the presence of steam. These findings underscore the significance of utilizing appropriate DFM and demonstrate the potential of CaL-BRM for efficient integrated carbon capture and utilization.