Development of Suitable CuO-Based Materials Supported on Al2O3, MgAl2O4, and ZrO2 for Ca/Cu H2 Production Process

CO2 Capture at Medium to High Temperature Using Solid Oxide-Based Sorbents: Fundamental Aspects, Mechanistic Insights, and Recent Advances

Carbon dioxide capture and mitigation form a key part of the technological response to combat climate change and reduce CO₂ emissions. Solid materials capable of reversibly absorbing CO₂ have been the focus of intense research for the past two decades, with promising stability and low energy costs to implement and operate compared to the more widely used liquid amines. In this review, we explore the fundamental aspects underpinning solid CO₂ sorbents based on alkali and alkaline earth metal oxides operating at medium to high temperature: how their structure, chemical composition, and morphology impact their performance and long-term use. Various optimization strategies are outlined to improve upon the most promising materials, and we combine recent advances across disparate scientific disciplines, including materials discovery, synthesis, and in situ characterization, to present a coherent understanding of the mechanisms of CO₂ absorption both at surfaces and within solid materials.

Atomic Layer Deposition of a Film of Al2O3 on Electrodeposited Copper Foams To Yield Highly Effective Oxygen Carriers for Chemical Looping Combustion-Based CO2 Capture

A rapid electrochemical deposition protocol is reported to synthesize highly porous Cu foams serving as model oxygen carriers for chemical looping, a promising technology to reduce anthropogenic CO₂ emission. To overcome the sintering-induced decay in the oxygen carrying capacity of unsupported Cu foams, Al₂O₃ films of different thicknesses (0.1-25 nm) are deposited onto the Cu foams via atomic layer deposition (ALD). An ALD-grown Al₂O₃ overcoat of 20 nm thickness (∼4 wt % Al₂O₃) is shown to be sufficient to ensure excellent redox cyclic stability. Al₂O₃-coated Cu foams exhibit a capacity retention of 96% over 10 redox cycles, outperforming their coprecipitated counterpart (equal Al₂O₃ content). The structural evolution of the stabilized foams is probed in detail and compared to benchmark materials to elucidate the stabilizing role of the Al₂O₃ overcoat. Upon heat treatment, the initially conformal Al₂O₃ overcoat induces a fragmentation of large Cu(O) branches into small particles. After multiple redox cycles, the Al₂O₃ overcoat transforms into sub-micrometer-sized grains of aluminum-containing phases (δ-Al₂O₃, CuAl₂O₄, and CuAlO₂) that are dispersed homogeneously within the CuO matrix. Finally, the diffusion of Cu through an Al₂O₃ layer upon heat treatment in an oxidizing atmosphere is probed in model thin films.