The poor interfacial contact between ion-conducting membrane and electrodes and the resulting sluggish mass transport has been long recognized as the hurdle for the further development of the electrochemical conversion...
To
improve the energy conversion efficiency and durability of zinc–air
batteries (ZABs) for large-scale implementations, here we propose
an “air-breathing” strategy to significantly enlarge
triple-interfaces with intensified mass transfer. By dip-coating the
aerophilic perfluorochemical compounds (PFC) and amphiphilic ionomers
into the self-supported electrodes, (1) the high solubility of O2 in the PFC nanoemulsions greatly increases triple-phase boundaries
and facilitates the efficient supply/removal of O2 from
the electrolyte; (2) the ionomers with hydrophobic and hydrophilic
functionalities enable fast gas, water, and ion transport to the triple-phase
boundaries; and (3) the self-supported electrode without binder ensures
fast electron transfer while the firm integration prevents catalyst
shedding. By applying this strategy, the ZABs show a high power density
of 115 mW cm–2 and a narrow discharge/charge gap
of 0.64 V at 10 mA cm–2 and a long-cycling durability
(over 1000 h). This work provides a universal approach to promote
gas-evolving reactions for electrochemical applications.
Electrosynthesis of ammonia from nitrate reduction receives extensive attention recently for its relatively mild conditions and clean energy requirements, while most existed electrochemical strategies can only deliver a low yield rate and short duration for the lack of stable ion exchange membranes at high current density. Here, a bipolar membrane nitrate reduction process is proposed to achieve ionic balance, and increasing water dissociation sites is delivered by constructing a three-dimensional physically interlocked interface for the bipolar membrane. This design simultaneously boosts ionic transfer and interfacial stability compared to traditional ones, successfully reducing transmembrane voltage to 1.13 V at up to current density of 1000 mA cm−2. By combining a Co three-dimensional nanoarray cathode designed for large current and low concentration utilizations, a continuous and high yield bipolar membrane reactor for NH3 electrosynthesis realized a stable electrolysis at 1000 mA cm−2 for over 100 h, Faradaic efficiency of 86.2% and maximum yield rate of 68.4 mg h−1 cm−2 with merely 2000 ppm NO3- alkaline electrolyte. These results show promising potential for artificial nitrogen cycling in the near future.
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