Heterogeneous electrochemical processes, including (photo)electrochemical water splitting to evolve hydrogen via semiconductors and/or electrocatalysts, are driven by the accumulation of charge carriers and thus the interfacial electrochemical potential gradients that promote charge transfer. Conventional electrochemical techniques measure/control potentials at the conductive substrate, but are unable to isolate processes and electrochemical potentials at the surface during operation.
1 In this talk, we will show that a nanoelectrode tip of an atomic force microscope cantilever can effectively sense the surface electrochemical potential of electrocatalysts
in operando.
2 First, we will discuss fundamental aspects and capabilities of the probes used.
3 We then will show how the technique allows for measurement of the surface potential and thickness-dependent electronic properties of cobalt (oxy)hydroxide phosphate (CoPi). We show that when CoPi is deposited on illuminated photoanodes like hematite (a-Fe
2O
3), it acts as both a hole collector and an oxygen evolution catalyst. We highlight the versatility of the technique by comparing surface potentials of CoPi-decorated planar and mesoporous hematite, as well as bismuth vanadate photoelectrodes.
References:
(1) Nellist, M. R.; Laskowski, F. A. L.; Lin, F.; Mills, T. J.; Boettcher, S. W. Semiconductor-Electrocatalyst Interfaces: Theory, Experiment, and Applications in Photoelectrochemical Water Splitting. Acc. Chem. Res. 2016, 49, 733–740.
(2) Nellist, M. R.; Laskowski, F. A. L.; Qiu, J.; Hajibabaei, H.; Sivula, K.; Hamann, T. W.; Boettcher, S. W. Potential-Sensing Electrochemical Atomic Force Microscopy for In-Operando Analysis of Electrocatalysis During (Photo)electrochemical Water Splitting. Accepted, Nature Energy 2017.
(3) Nellist, M. R.; Chen, Y.; Mark, A.; Gödrich, S.; Stelling, C.; Jiang, J.; Poddar, R.; Li, C.; Kumar, R.; Papastavrou, G.; Retsch, M.; Brunschwig, B. S.; Huang, Z.; Xiang, C.; Boettcher, S. W. Atomic Force Microscopy with Nanoelectrode Tips for High Resolution Electrochemical, Nanoadhesion and Nanoelectrical Imaging. Nanotechnology 2017, 28, 95711.
