(571e) Oxidation-Tolerant Ni-Based Dual-Function Materials for Reactive Carbon Capture

Reactive carbon capture (RCC) has emerged as a promising strategy for CO₂ capture and conversion within the same system, using a single material for both functions. Unlike conventional carbon capture and utilization (CCU) methods that require separate reactors and energy-intensive CO₂ desorption and transport steps, RCC enables in-situ capture and conversion. This is facilitated by dual-function materials (DFMs), which integrate a CO₂ sorbent and a catalytic component on the same support. However, under realistic flue gas conditions containing oxidants such as O₂ and H₂O, the catalytic performance of DFMs is often compromised. In particular, Ni-based catalysts, while cost-effective and widely studied, exhibit poor stability and activity in oxidizing environments, necessitating the use of precious metals (eg. Ru, Pt), dopants, or promoters to enhance their performance. Additionally, conventional Ni-based DFMs require high temperatures for reduction following oxidation, further limiting their practical applicability.

In this work, we synthesize Ni nanocrystals via colloidal synthesis and incorporate them into DFMs to evaluate their CO₂ capture and conversion performance under various reactive conditions. Notably, these colloidal Ni-based DFMs exhibit CO₂ capture and subsequent conversion to methane (CH₄) even in the presence of both O₂ and H₂O, in contrast to previous literature reports. The highest CO₂ capture and CH₄ production occur in a diluted CO₂-alone atmosphere. While CO₂ uptake remains largely unaffected in the presence of oxidants, CH₄ production decreases with increasing oxidant concentrations. Nevertheless, CH₄ formation persists even under these conditions, and the performance is maintained over three consecutive RCC cycles. Additionally, the synthesized DFMs outperform previously reported Ni-based systems under comparable conditions.

We attribute this enhanced performance to the small particle size and narrow size distribution of the Ni nanocrystals, which facilitate efficient reduction at moderate temperatures. Unlike conventional Ni DFMs that require elevated temperatures for reduction, our materials enable isothermal operation at 350°C, thereby improving overall process efficiency. These findings highlight the potential of colloidal Ni nanocrystals as a promising platform for RCC applications, offering improved stability and catalytic activity in oxidizing environments, and eliminating the need for expensive precious metal catalysts.