Chloride-Engineered CO Selectivity Promotion in Integrated Carbon Capture and Hydrogenation

Achieving high CO selectivity in integrated carbon capture and hydrogenation (ICCH) remains a challenge because Ni-based dual functional materials (DFMs) inevitably catalyze competing methanation. Here, we demonstrate that trace chloride incorporation into Ni–Ca DFMs switches the dominant hydrogenation pathway from methanation to the reverse water−gas shift reaction. Chloride preferentially interacts with the CaO sorbent phase, forming Ca–Cl species that drive CaO densification and substantially lower the reducibility of the adjacent Ni active sites. Consequently, the 1% Cl-modified DFM attains 91.6% CO selectivity at 600 °C, in contrast to the 20.5% CO selectivity of the Cl-free counterpart. Cyclic testing confirms that the Cl-modified DFM maintains stable CO2 conversion and high CO selectivity. In situ experiments further show that chloride suppresses the deep hydrogenation of formate intermediates, thereby terminating the reaction at the CO-forming step rather than proceeding to CH4. This study establishes halogen engineering as an effective and operationally simple strategy for steering product selectivity in ICCH processes.