Influence of High-Temperature Steam on the Reactivity of CaO Sorbent for CO₂ Capture

Calcium looping is a high-temperature CO₂ capture technology applicable to the postcombustion capture of CO₂ from power station flue gas, or integrated with fuel conversion in precombustion CO₂ capture schemes. The capture technology uses solid CaO sorbent derived from natural limestone and takes advantage of the reversible reaction between CaO and CO₂ to form CaCO₃; that is, to achieve the separation of CO₂ from flue or fuel gas, and produce a pure stream of CO₂ suitable for geological storage. An important characteristic of the sorbent, affecting the cost-efficiency of this technology, is the decay in reactivity of the sorbent over multiple CO₂ capture-and-release cycles. This work reports on the influence of high-temperature steam, which will be present in flue (about 5–10%) and fuel (∼20%) gases, on the reactivity of CaO sorbent derived from four natural limestones. A significant increase in the reactivity of these sorbents was found for 30 cycles in the presence of steam (from 1–20%). Steam influences the sorbent reactivity in two ways. Steam present during calcination promotes sintering that produces a sorbent morphology with most of the pore volume associated with larger pores of ∼50 nm in diameter, and which appears to be relatively more stable than the pore structure that evolves when no steam is present. The presence of steam during carbonation reduces the diffusion resistance during carbonation. We observed a synergistic effect, i.e., the highest reactivity was observed when steam was present for both calcination and carbonation

Redox-Driven Restructuring of FeMnZr-Oxygen Carriers Enhances the Purity and Yield of H₂ in a Chemical Looping Process

Chemical looping-based approaches allow for the production of high purity hydrogen from methane with an inherent separation of the coproduced carbon dioxide. In such a process, first methane is oxidized using lattice oxygen from a solid oxygen carrier. In the second half-cycle, the reduced oxygen carrier is reoxidized with steam to yield hydrogen. In this work, we report on the development of an iron-based oxygen carrier with an excellent redox stability and probe the synergistic effect of adding Mn₂O₃ and ZrO₂, leading to an enhancement of the reactivity of iron oxide with methane and increasing the hydrogen yield over multiple redox cycles. The promoting effects of Mn₂O₃ and ZrO₂ in the oxygen carrier were elucidated by combining TPR, STEM-EDX, reactivity tests, and conductivity measurements complemented by SIMS analysis. The addition of ZrO₂ promoted the oxidation reactivity of the material, whereas the addition of Mn₂O₃ accelerated the reduction of iron oxide. Conductivity measurements revealed that the addition of Mn₂O₃ lowers the activation energy for charge transfer, providing an explanation for the improved cyclic redox performance of the oxygen carriers. A redox-driven surface modification that results in the formation of an (Fe,Mn)O phase was found to retard effectively the cracking of methane on surface iron, leading to a high resistance to carbon deposition and in turn a high purity of the hydrogen produced. The observations reported here illustrate the importance of charge transfer characteristics for chemical looping based redox processes and open new perspectives for the design of more efficient oxygen carriers

Renewable Energy from Livestock Waste Valorization: Amyloid-Based Feather Keratin Fuel Cells

Increasing carbon emissions have accelerated climate change, resulting in devastating effects that are now tangible on an everyday basis. This is mirrored by a projected increase in global energy demand of approximately 50% within a single generation, urging a shift from fossil-fuel-derived materials toward greener materials and more sustainable manufacturing processes. Biobased industrial byproducts, such as side streams from the food industry, are attractive alternatives with strong potential for valorization due to their large volume, low cost, renewability, biodegradability, and intrinsic material properties. Here, we demonstrate the reutilization of industrial chicken feather waste into proton-conductive membranes for fuel cells, protonic transistors, and water-splitting devices. Keratin was isolated from chicken feathers via a fast and economical process, converted into amyloid fibrils through heat treatment, and further processed into membranes with an imparted proton conductivity of 6.3 mS cm–1 using a simple oxidative method. The functionality of the membranes is demonstrated by assembling them into a hydrogen fuel cell capable of generating 25 mW cm–2 of power density to operate various types of devices using hydrogen and air as fuel. Additionally, these membranes were used to generate hydrogen through water splitting and in protonic field-effect transistors as thin-film modulators of protonic conductivity via the electrostatic gating effect. We believe that by converting industrial waste into renewable energy materials at low cost and high scalability, our green manufacturing process can contribute to a fully circular economy with a neutral carbon footprint

Renewable Energy from Livestock Waste Valorization: Amyloid-Based Feather Keratin Fuel Cells

Increasing carbon emissions have accelerated climate change, resulting in devastating effects that are now tangible on an everyday basis. This is mirrored by a projected increase in global energy demand of approximately 50% within a single generation, urging a shift from fossil-fuel-derived materials toward greener materials and more sustainable manufacturing processes. Biobased industrial byproducts, such as side streams from the food industry, are attractive alternatives with strong potential for valorization due to their large volume, low cost, renewability, biodegradability, and intrinsic material properties. Here, we demonstrate the reutilization of industrial chicken feather waste into proton-conductive membranes for fuel cells, protonic transistors, and water-splitting devices. Keratin was isolated from chicken feathers via a fast and economical process, converted into amyloid fibrils through heat treatment, and further processed into membranes with an imparted proton conductivity of 6.3 mS cm–1 using a simple oxidative method. The functionality of the membranes is demonstrated by assembling them into a hydrogen fuel cell capable of generating 25 mW cm–2 of power density to operate various types of devices using hydrogen and air as fuel. Additionally, these membranes were used to generate hydrogen through water splitting and in protonic field-effect transistors as thin-film modulators of protonic conductivity via the electrostatic gating effect. We believe that by converting industrial waste into renewable energy materials at low cost and high scalability, our green manufacturing process can contribute to a fully circular economy with a neutral carbon footprint