The Effect of Alkali Metals (Li, Na, and K) on Ni/CaO Dual-Functional Materials for Integrated CO₂ Capture and Hydrogenation

Abstract

Ni/CaO, a low-cost dual-functional material (DFM), has been widely studied for integrated CO2 capture and hydrogenation. The core of this dual-functional material should possess both good CO2 capture–conversion performance and structural stability. Here, we synthesized Ni/CaO DFMs modified with alkali metals (Na, K, and Li) through a combination of precipitation and combustion methods. It was found that Na-modified Ni/CaO (Na-Ni/CaO) DFM offered stable CO2 capture–conversion activity over 20 cycles, with a high CO2 capture capacity of 10.8 mmol/g and a high CO2 conversion rate of 60.5% at the same temperature of 650 °C. The enhanced CO2 capture capacity was attributed to the improved surface basicity of Na-Ni/CaO. In addition, the incorporation of Na into DFMs had a favorable effect on the formation of double salts, which shorten the CO2 capture and release process and promoted DFM stability by hindering their aggregation and the sintering of DFMs.

Keywords

• alkali metal
• Ni/CaO
• dual-functional material
• CO₂ capture and hydrogenation
• reverse water–gas shift