This study aims to design a porous Janus polyacrylonitrile-based carbon fiber (PCF) electrode with asymmetric interfacial wettability for the simultaneous management on oxygen diffusion and ion transfer for H 2 O 2 electro-generation. The wetting state of PCF electrode is adjusted by the facile deposition of polytetrafluoroethylene (PTFE) via capillarity. In contrast to single aerophobic and aerophilic electrodes, the Janus PCF electrodes provide a stable gas film for promoting oxygen transfer while ensuring rapid ion migration and release. Compared to the other Janus electrodes, the porous PCF electrode subjected to three cycles of PTFE modification (named Janus-3) exhibit richer functional groups that improves two-electron oxygen reduction reaction (2e − -ORR) performance with reduced onset potential and higher current increase rate. And the excellent characteristics of Janus-3 contribute to the highest H 2 O 2 production rate of 10.61 ± 0.13 mg h −1 cm −2 in a flow-through electrochemical system, along with the highest current efficiency (CE) and oxygen utilization efficiency (OUE) values of 83.63 ± 1.01 % and 81.22 ± 4.13 %, respectively. The oxygen mass transfer and ion transport mechanism of H 2 O 2 electro-generation are revealed. Lastly, long-lasting operation stability of Janus-3 and its high H 2 O 2 production, CE, and OUE suggest great potential to replace normal gas diffusion electrodes for H 2 O 2 electro-generation.
Yuan Zhou,Shaojie Zheng,Xiao Cheng,Liu Liu,Hao Lei,Nianbing Zhong,Zhichao Deng,Wenqian Zhang,Xuefeng He
Direct liquid fuel cells (DLFCs) offer a promising alternative energy solution by directly utilizing "liquid sunshine fuels", thereby avoiding the complexities of hydrogen storage systems. Despite their potential, DLFC performance is often compromised by gas bubble accumulation at the anode, which reduces the active electrochemical surface area and disrupts fuel transport. In this study, we introduce an inspired Janus electrode with combined hydrophobic and hydrophilic properties designed to shorten the gas diffusion pathway, promoting efficient in-situ bubble release and improving mass transfer. Using visualization techniques, finite element analysis, and mechanical modeling, we investigated the dynamic behavior and transport mechanisms of gas bubbles. The results demonstrate that DLFCs equipped with Janus electrodes achieve superior performance at high current densities, reducing voltage fluctuations and optimizing gas-liquid two-phase flow. This work suggests that Janus electrodes can effectively overcome the bubble-induced limitations in conventional DLFCs.
The bubbles electrochemically generated by gas evolution reactions are commonly driven off the electrode by buoyancy, a weak force used to overcome bubble adhesion barriers, leading to low gas-transporting efficiency. Herein, a Janus electrode with asymmetric wettability has been prepared by modifying two sides of a porous stainless-steel mesh electrode, with superhydrophobic polytetrafluoroethylene (PTFE) and Pt/C (or Ir/C) catalyst with well-balanced hydrophobicity, respectively, affording unidirectional transportation of as-formed gaseous hydrogen and oxygen from the catalyst side to the gas-collecting side during water splitting. “Bubble-free” electrolysis was realized while “floating” the Janus electrode on the electrolyte. Antibuoyancy through-mesh bubble transportation was observed while immersing the electrode with the PTFE side downward. The wettability gradient within the electrode endowed sticky states of bubbles on the catalyst side, resulting in efficient bubble-free gas transportation with 15-fold higher current density than submerged states.
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