Harnessing Ammonia as a Hydrogen Carrier for Integrated CO₂ Capture and Reverse Water–Gas Shift

In this paper, a concept of integrated CO 2 capture and reverse water–gas shift (ICCrWGS) process was proposed using NH 3 as the H 2 carrier. The CO 2 efficiency and total thermal energy consumption for the conventional rWGS, ICCrWGS using H 2 (H 2 -ICCrWGS) and NH 3 (NH 3 -ICCrWGS), were calculated. ICCrWGS using H 2 and NH 3 was conducted over the thermally stable Ni/CaZr dual-function materials (DFMs). NH 3 decomposition, CO 2 capture capacity, CO 2 conversion, and CO selectivity were addressed at different reaction temperatures, and the optimal temperature was determined to be 650 °C. The Ni/CaZr DFMs exhibited stable CO 2 capture capacity and CO productivity during ICCrWGS using the NH 3 carrier. A carbonate spillover mechanism for CO production over the Ni/CaZr DFMs in NH 3 -ICCrWGS was proposed using in situ diffuse reflectance infrared Fourier transform spectroscopy. It was found that CO is produced from the bridged bidentate carbonate route in the Ni–CaO interface.