Measurement and control of oxygen non-stoichiometry in praseodymium-cerium oxide thin films by coulometric titration
Not provided.
Materials Science↗
Engineering topics
Zhao, Yun
Publications and source records attributed to Zhao, Yun.
Poly(aryl piperidinium) polymers including those with stable cationic pendant groups for use as anion exchange membranes and ionomers
Poly(aryl piperidinium) polymers with pendant cationic groups are provided which have an alkaline-stable cation, piperidinium, introduced into a rigid aromatic polymer backbone free of ether bonds. Hydroxide exchange membranes or hydroxide exchange ionomers formed from these polymers exhibit superior chemical stability, hydroxide conductivity, decreased water uptake, good solubility in selected solvents, and improved mechanical properties in an ambient dry state as compared to conventional hydroxide exchange membranes or ionomers. Hydroxide exchange membrane fuel cells comprising the poly(aryl piperidinium) polymers with pendant cationic groups exhibit enhanced performance and durability at relatively high temperatures.
Yan, Yushan↗
A high-performance hydroxide exchange membrane enabled by Cu 2+ -crosslinked chitosan
We report ion exchange membranes are widely used to selectively transport ions in various electrochemical devices. Hydroxide exchange membranes (HEMs) are promising to couple with lower cost platinum-free electrocatalysts used in alkaline conditions, but are not stable enough in strong alkaline solutions. Herein, we present a Cu 2+ -crosslinked chitosan (chitosan-Cu) material as a stable and high-performance HEM. The Cu 2+ ions are coordinated with the amino and hydroxyl groups of chitosan to crosslink the chitosan chains, forming hexagonal nanochannels (similar to 1nm in diameter) that can accommodate water diffusion and facilitate fast ion transport, with a high hydroxide conductivity of 67 ms cm -1 at room temperature. The Cu 2+ coordination also enhances the mechanical strength of the membrane, reduces its permeability and, most importantly, improves its stability in alkaline solution (only 5% conductivity loss at 80 degrees C after 1,000 h). These advantages make chitosan-Cu an outstanding HEM, which we demonstrate in a direct methanol fuel cell that exhibits a high power density of 305 mWcm -2 . The design principle of the chitosan-Cu HEM, in which ion transport channels are generated in the polymer through metal-crosslinking of polar functional groups, could inspire the synthesis of many ion exchange membranes for ion transport, ion sieving, ion filtration and more.
36 MATERIALS SCIENCE↗