Special Section on Mass and Charge Transport in Fuel Cells and Metal-ion Batteries

Given the increasing energy demand and carbon dioxide emission, countries all over the world are vigorously developing sustainable and clean energy. Fuel cells and metal-ion batteries that directly convert chemical energy into electric energy have been receiving ever-increasing attention for energy conversion and storage in several applications such as portable, mobile, and stationary applications. Nowadays, not understanding mass and charge transport in fuel cells and metal-ion batteries, which results in low performance and durability, are still challenges for their large-scale commercialization. For example, the insufficient interaction of catalyst/ionomer/reactant as a result of fuel cells lacking the ion-conducting, reactant-delivering, or proton-conducting pathways leads to the deactivated triple-phase boundary. Meanwhile, the metal-ions transport in the interface of solid active materials and electrolyte, and the charge transport including ions transport in the electrolyte, and electron transport in the solid phase, are not well known in advanced metal-ion batteries. An ideal electrode architecture that boosts the performance and durability of cells and batteries needs the electrode design to meet all the requirements of electrochemical kinetics and mass and charge transport characteristics.

INVESTIGATION OF PHYSICAL PRINCIPLES OF RESISTIVE SWITCHING IN RERAM STRUCTURES BASED ON HAFNIUM OXIDE

In this paper, the physical principles of resistive switching in the Au/Ti/HfO2/Au/Si memristor are investigated, including oxygen ions transport, heat transfer and electric current flow through the structure.

COATING FOR PROTECTION OF CONCRETE FROM SULFATES

Durability of reinforced concrete is one of the main demands in civil engineering.Operating conditions, particularly in aggressive mediums, determine durability of constructions.Sulfate mediums are among the most aggressive ones which cause steel reinforcement corrosion. Themodern requirements for high consistency fresh concretes are governed by practice. This way thedisturbance of reinforcement passive state can be caused by changes in hardened concrete especiallyin aggressive mediums. Thus, the restriction of SO42- ions transport in concretes, which are obtainedfrom high consistency fresh mixes and exploited in sulfate mediums, can be considered as an actualproblem.The paper is devoted to protection of concrete surface by coating based on alkali-activatedaluminosilicate binder from SO42- ions transport to prevent steel reinforcement corrosion. It wasshown that the coating with thickness of 3 mm ensures total concrete protection. It was revealed thatpermeability of concrete depending on cation decreases in the row (NH4)2SO4>Na2SO4>MgSO4. Theprotective function of coating was simulated by application of mentioned salts as admixtures. LesspH values of water extracts of the binder during hydration while using of 2.5 % MgSO4 is evidenceof advanced crystallinity of zeolite-like sulfate-containing hydroaluminosilicates with participationof Mg2+ ions equal to Са2+ ions. While content of (NH4)2SO4 was increased up to 5.0 % less pH wasfixed due to decelerated formation of zeolite-like minerals. Stability of pH values in presence ofNa2SO4 (0.5…2.5 %) was caused by no influence on structure formation. Thus, the restriction of SO 2-ions transport in protective coating is due to their binding by alkaline aluminosilicate binder inzeolite-like minerals with higher crystallinity due to presence of Na+, NH + and Mg2+ cations fromsulfates.

Unidirectional ion transport in nanoporous carbon membranes with a hierarchical pore architecture

The transport of fluids in channels with diameter of 1-2 nm exhibits many anomalous features due to the interplay of several genuinely interfacial effects. Quasi-unidirectional ion transport, reminiscent of the behavior of membrane pores in biological cells, is one phenomenon that has attracted a lot of attention in recent years, e.g., for realizing diodes for ion-conduction based electronics. Although ion rectification has been demonstrated in many asymmetric artificial nanopores, it always fails in the high-concentration range, and operates in either acidic or alkaline electrolytes but never over the whole pH range. Here we report a hierarchical pore architecture carbon membrane with a pore size gradient from 60 nm to 1.4 nm, which enables high ionic rectification ratios up to 104 in different environments including high concentration neutral (3 M KCl), acidic (1 M HCl), and alkaline (1 M NaOH) electrolytes, resulting from the asymmetric energy barriers for ions transport in two directions. Additionally, light irradiation as an external energy source can reduce the energy barriers to promote ions transport bidirectionally. The anomalous ion transport together with the robust nanoporous carbon structure may find applications in membrane filtration, water desalination, and fuel cell membranes.

Layered double hydroxide membrane with high hydroxide conductivity and ion selectivity for energy storage device

Membranes with fast and selective ions transport are highly demanded for energy storage devices. Layered double hydroxides (LDHs), bearing uniform interlayer galleries and abundant hydroxyl groups covalently bonded within two-dimensional (2D) host layers, make them superb candidates for high-performance membranes. However, related research on LDHs for ions separation is quite rare, especially the deep-going study on ions transport behavior in LDHs. Here, we report a LDHs-based composite membrane with fast and selective ions transport for flow battery application. The hydroxide ions transport through LDHs via vehicular (standard diffusion) & Grotthuss (proton hopping) mechanisms is uncovered. The LDHs-based membrane enables an alkaline zinc-based flow battery to operate at 200 mA cm−2, along with an energy efficiency of 82.36% for 400 cycles. This study offers an in-depth understanding of ions transport in LDHs and further inspires their applications in other energy-related devices.