Electron Transfer Imaging Realized in Electrocatalysis Process

23 Nov.,2022


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Recently, researchers from the Molecular Catalysis and In-situ Characterization Research Team of the National Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, have made new progress in the research of liquid-phase in-situ electrochemical imaging, realizing the nano-scale intuitive imaging of the charge transfer process in the electrocatalytic process. It is observed that the metal electrode has a spatially varying internal potential difference within the interface at the micro-nano scale, which breaks through people's understanding of the electron transfer process in traditional electrochemistry.

The intrinsic driving force of the electrochemical reaction is the electrochemical potential, whose determinant is the potential difference within the interface, namely electron transfer. How to detect the local distribution of the interface potential and reveal its internal relationship with the electron transfer kinetics is of great importance for the understanding of the reaction mechanism of the nanocatalyst. For a long time, researchers have been envisaging the use of nanoprobes to observe the electron transfer in the reaction process, but the current at this scale is extremely weak and is often disturbed by external noise. In addition, the diffusion process of chemical species in the liquid phase often makes electrochemical imaging difficult to stabilize. More importantly, in the electrocatalytic process, the catalytic reaction is convoluted with the electron transfer process, making the latter difficult to detect directly.

The Team established a characterization method combining atomic force microscopy with nanometer spatial resolution and scanning electrochemical imaging. The method uses the movement scanning of the nanoprobe to measure the local distribution of the outer spherical electron pair molecules and the catalytic product molecules capable of transferring electrons, and realizes the in-situ reaction imaging of the electron transfer process and the electrocatalytic reaction process. The electron transfer imaging on metal nanoparticles found that the process presents site-dependent spatial heterogeneity, breaking through people's microscopic understanding of the electron transfer process on metal electrodes. At the same time, a series of fine experiments, such as decoupling the interference of the mass transfer effect on the interface electron transfer, extracting rate constant by the finite element method of mathematical modeling, and measuring internal potential difference, reveals the linear relationship between the spatially varying potential difference within the interface and the logarithm of the electron transfer rate constant. This method provides new ideas for realizing in-situ observation of the electron transfer process and the catalytic reaction in the electrochemical field, the development of the in-situ imaging technology, and the detection of electrocatalytic process mechanism.