Jia Gao,Rui-Yang Zhao,Yi-Guang Wang,Ruo-Chen Xie,Wei Wang
We present a fluorescent microscopic method using an ultra-pH-sensitive polymeric probe to rapidly map within subsecond the pH distribution resulting from oxygen reduction reaction electrocatalysed by an array of platinum nanoparticles. Upon voltammetry of the surface-supported Pt catalysts, fluorescent quenching waves are observed to depend on the electrode potential. The spatiotemporal fluorescent evolution is then confirmed under a constant potential control to be due to the local pH change as a function of diffusing time by an estimation of the proton diffusion coefficient ( L α t 1 / 2 ) . On these bases, the fluorescent measurements at short reaction times can provide quantitative information regarding the one and two dimensional pH distributions, which are shown to exhibit the expected shape of a typical diffusion-driven concentration gradient. Such imaging of proton/pH profiles may find important applications such as efficient screening of different micro/nanoscale electrocatalysts.
Anion exchange membrane water electrolysis (AEMWE) offers an opportunity to use inexpensive nonprecious metal catalysts. However, pure water-fed AEMWE still faces issues of durability. Herein, we compared the stability of AEMWE under different anolytes, including KOH, pure water, and a phosphate buffer (PB) using a NiFeCo oxygen evolution reaction catalyst. Upon thoroughly characterizing several changes before/after 100 h durability tests, such as the cell performance, catalyst dissolution, catalyst morphologies, impedance of the anion exchange membrane, and catalytic layer, we speculate that the change of the local pH is the main factor causing catalyst reconstruction, which further leads to the loss of cell performance in the pure water-fed mode. By using PB to control the local pH, the morphology of the catalyst will no longer change after the durability test, and the cell performance can recover to the initial performance in pure water. These results not only indicate that the catalyst structural transformation is the main reason for the deactivation of pure water-fed AEMWE but also help find a way to achieve highly durable pure water-fed AEMWE.
危险品化学品经营许可证（带存储）