In situ electrochemistry in TEM with controlled mass transport for electro-conversion

Abstract text (incl. figure legends and references)

Introduction

In order to overcome the current energy challenges, the study of new materials for energy or feedstocks conversion becomes urgent. Liquid Phase Transmission Electron Microscopy (LPTEM) combined with electrodes for electrochemistry is a relevant technique for innovation in electro-conversion.

Objectives

We present an electrochemical flow Nano-Cell (LPTEM) allowing in situ observation of materials in relevant reaction conditions. It combines the advantages of ultra-microelectrodes - probing fast kinetics - and microfluidics(1) to switch from mass transport- to electron transfer rate-limited reaction kinetics, with the high resolution imaging capabilities of TEM and its chemical analysis toolbox, allowing the study of catalytic nanoparticles in operando or their synthesis.

The redox kinetics are controlled in this flow cell configuration by flow rate control and electrical potential control in liquid using microfabricated electrodes. We address how to limit radiolysis from a microfabrication point and which electrode materials can best link classic electrochemical methods to LPTEM conditions.

Materials & methods

In order to characterize the MEMS-based Nano-Cell mass transport characteristics, a one electron redox molecule with fast electron transfer rate is used experimentally and modelled using finite element analysis.

Results

We show the stability of both flow and electric potential in our LPTEM Nano-Cell (Figure 1) and show examples of in situ nanoparticle synthesis

Conclusion

This technique can lead to new insights in catalysts synthesis for electro-conversion by linking a material"s nanoscale morphology to its functionality.

Figure 1: Cyclic voltammetry of 1mM Ferrocenemethanol + 0.1M KCl, for different flowrates using the same Nano-Cell. For each flowrate value, 10 cycles were run at 10mV/s. The plots overlapping shows the stability of the electric potential measurement and flow speed at the electrode surface.

References

1 I. Dumitrescu, D. F. Yancey and R. M. Crooks, Lab Chip, 2012, 12, 986.