Ni-CaO dual function materials prepared by different synthetic modes for integrated CO₂ capture and conversion

Dual-functional materials (DFMs) present broad prospects in CO₂ capture and in-situ conversion to value-added products using renewable energy. Herein, we proposed and demonstrated three different synthetic modes for preparing Ni-CaO DFMs using carbide slag as calcium precursor. CO₂ sorption and in-situ hydrogenation performance of the Ni-CaO DFMs was evaluated using a fixed-bed reactor. Results indicated that CO₂ sorption capacity and CO productivity of the synthesized Ni-CaO DFMs depended on the synthetic modes. The desired Ni/CS-P30-C synthesized by acid pretreatment of carbide slag followed by citric acid complex exhibited a high CO₂ sorption capacity (13.28 mmol/g DFMs) and a great CO productivity (5.12 mmol/g DFMs) under the isothermal testing temperature of 650 °C. The sample also showed stable CO₂ uptake and CO productivity within 17 cycles. The good CO₂ sorption and in-situ hydrogenation performance were associated with the better textural properties, smaller particle size and more uniform dispersion of Ni species, which were resulted from propionic acid pretreatment and citric acid complex processes. In addition, Ni-CaO pellet with high mechanical strength (2.88 MPa) and abrasion ability (weight loss of 2.36% after 3000 rotations). had also been prepared by the extrusion-spheronization method. The pelletization process adversely affected the CO₂ sorption and in-situ hydrogenation performance, but the pellet exhibited good stability in cyclic operations.