Carbon dioxide (CO2) capture by gas-separation membranes has become increasingly attractive due to its high energy efficiency, relatively low cost, and environmental impact. Polyvinylamine (PVAm)-based facilitated transport (FT) membranes were developed in the last decade for CO2 capture. This work discusses the challenges of applying PVAm-based FT membranes from materials to processes for postcombustion CO2 capture in power plants and cement factories. Experiences learned from a pilot demonstration system can be used to guide the design of other membranes for CO2 capture. The importance of module and process design is emphasized in the achievement of a high-performance membrane system. Moreover, the results from process simulation and cost estimation indicate that a three-stage membrane system is feasible for achieving a high CO2 purity of 95 vol%. The specific CO2 capture cost was found to significantly depend on the required CO2 capture ratio, and a moderate CO2 capture ratio of 50% presented a cost of 63.7 USD per tonne CO2 captured. Thus, FT membrane systems were found to be more competitive for partial CO2 capture.
One-dimensional (1D) Pt-based electrocatalysts demonstrate outstanding catalytic activities and stability toward the oxygen reduction reaction (ORR). Advances in three-dimensional (3D) ordered electrodes based on 1D Pt-based nanostructure arrays have revealed great potential for developing highperformance proton exchange membrane fuel cells (PEMFCs), in particular for addressing the mass transfer and durability challenges of Pt/C nanoparticle electrodes. This paper reviews recent progress in the field, with a focus on the 3D ordered electrodes based on self-standing Pt nanowire arrays. Nanostructured thin-film (NSTF) catalysts are discussed along with electrodes made from Pt-based nanoparticles deposited on arrays of polymer nanowires, and carbon and TiO2 nanotubes. Achievements on electrodes from Pt-based nanotube arrays are also reviewed. The importance of size, surface properties, and the distribution control of 1D catalyst nanostructures is indicated. Finally, challenges and future development opportunities are addressed regarding increasing electrochemical surface area (ECSA) and quantifying oxygen mass transport resistance for 1D nanostructure array electrodes.
Interactions involving chemical reagents, solid particles, gas bubbles, liquid droplets, and solid surfaces in complex fluids play a vital role in many engineering processes, such as froth flotation, emulsion and foam formation, adsorption, and fouling and anti-fouling phenomena. These interactions at the molecular, nano-, and micro scale significantly influence and determine the macroscopic performance and efficiency of related engineering processes. Understanding the intermolecular and surface interactions in engineering processes is of both fundamental and practical importance, which not only improves production technologies, but also provides valuable insights into the development of new materials. In this review, the typical intermolecular and surface interactions involved in various engineering processes, including Derjaguin–Landau–Verwey–Overbeek (DLVO) interactions (i.e., van der Waals and electrical doublelayer interactions) and non-DLVO interactions, such as steric and hydrophobic interactions, are first introduced. Nanomechanical techniques such as atomic force microscopy and surface forces apparatus for quantifying the interaction forces of molecules and surfaces in complex fluids are briefly introduced. Our recent progress on characterizing the intermolecular and surface interactions in several engineering systems are reviewed, including mineral flotation, petroleum engineering, wastewater treatment, and energy storage materials. The correlation of these fundamental interaction mechanisms with practical applications in resolving engineering challenges and the perspectives of the research field have also been discussed.