High Free Volume Polyelectrolytes for Anion Exchange Membrane Water Electrolyzers with a Current Density of 13.39 A cm-2 and a Durability of 1000 h.

The rational design of the current anion exchange polyelectrolytes (AEPs) is challenging to meet the requirements of both high performance and durability in anion exchange membrane water electrolyzers (AEMWEs). Herein, highly-rigid-twisted spirobisindane monomer is incorporated in poly(aryl-co-aryl piperidinium) backbone to construct continuous ionic channels and to maintain dimensional stability as promising materials for AEPs. The morphologies, physical, and electrochemical properties of the AEPs are investigated based on experimental data and molecular dynamics simulations. The present AEPs possess high free volumes, excellent dimensional stability, hydroxide conductivity (208.1 mS cm-1 at 80 °C), and mechanical properties. The AEMWE of the present AEPs achieves a new current density record of 13.39 and 10.7 A cm-2 at 80 °C by applying IrO2 and nonprecious anode catalyst, respectively, along with outstanding in situ durability under 1 A cm-2 for 1000 h with a low voltage decay rate of 53 µV h-1 . Moreover, the AEPs can be applied in fuel cells and reach a power density of 2.02 W cm-2 at 80 °C under fully humidified conditions, and 1.65 W cm-2 at 100 °C, 30% relative humidity. This study provides insights into the design of high-performance AEPs for energy conversion devices.

Triptycene Branched Poly(aryl-co-aryl piperidinium) Electrolytes for Alkaline Anion Exchange Membrane Fuel Cells and Water Electrolyzers.

Alkaline polymer electrolytes (APEs) are essential materials for alkaline energy conversion devices such as anion exchange membrane fuel cells (AEMFCs) and water electrolyzers (AEMWEs). Here, we report a series of branched poly(aryl-co-aryl piperidinium) with different branching agents (triptycene: highly-rigid, three-dimensional structure; triphenylbenzene: planar, two-dimensional structure) for high-performance APEs. Among them, triptycene branched APEs showed excellent hydroxide conductivity (193.5 mS cm-1 @80 °C), alkaline stability, mechanical properties, and dimensional stability due to the formation of branched network structures, and increased free volume. AEMFCs based on triptycene-branched APEs reached promising peak power densities of 2.503 and 1.705 W cm-2 at 75/100 % and 30/30 % (anode/cathode) relative humidity, respectively. In addition, the fuel cells can run stably at a current density of 0.6 A cm-2 for 500 h with a low voltage decay rate of 46 µV h-1 . Importantly, the related AEMWE achieved unprecedented current densities of 16 A cm-2 and 14.17 A cm-2 (@2 V, 80 °C, 1 M NaOH) using precious and non-precious metal catalysts, respectively. Moreover, the AEMWE can be stably operated under 1.5 A cm-2 at 60 °C for 2000 h. The excellent results suggest that the triptycene-branched APEs are promising candidates for future AEMFC and AEMWE applications.

Synthesis of V-doped In2O3 Nanocrystals via Digestive-Ripening Process and Their Electrocatalytic Properties in CO2 Reduction Reaction.

The development of synthetic methods for monodisperse nanomaterial is of great importance in science and technology related to nanomaterials. The strong demands to prepare exceptionally monodisperse nanocrystals have made digestive-ripening one of the most sought-after size-focusing processes. Although digestive-ripening processes have been demonstrated to produce various metals and semiconductors, their applicability to oxides has rarely been studied despite various unique properties and applications of oxide nanomaterials. In this work, we demonstrate the successful synthesis of monodisperse V-doped In2O3 nanocrystals via a modified digestive-ripening process. The nanocrystals have truncated octahedral shape faceted with eight (222) and six (220) planes. To the best of our knowledge, this is the first report on the digestive-ripening synthesis of highly symmetrical doped oxide nanocrystals. Moreover, V-doped In2O3 nanocrystals exhibit electrocatalytic activities for CO2 electrochemical reduction and produce CH3OH, which has not been attainable from previously reported electrocatalysts based on indium or indium oxide. This distinctive catalytic property of V-doped In2O3 is attributed to the presence of V-dopants in the In2O3 host. Our demonstration has important implications for both nanocrystal synthesis and electrocatalyst development.