We start with Mike covering interfacial charge transfer at the semiconductor-catalyst interface – an issue that is central for solar water splitting yet has been poorly understood. New insights require unique experimental approaches- such as using a nanoelectrode AFM-SECM probe, scanning the surface of at water splitting photoanode, and making local surface potential measurements, in operando. In this presentation, we will discuss fundamental aspects and capabilities of the probes used.
We then 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-Fe2O3), it acts as both a hole collector and an oxygen evolution catalyst. The versatility of the technique is highlighted by comparing surface potentials of CoPi-decorated hematite and bismuth vanadate photoelectrodes.
Following Mike’s presentation, Teddy provides an overview of Bruker’s new capabilities for nanoelectrical characterization in liquid. Nanoscale electrical measurements with AFM are common – in air, and extremely challenging in liquid. At Bruker we recently developed insulated nanoelectrode AFM-SECM tips, which enable first and only nanoscale electrical characterization in liquid by a commercial solution. In addition, we have also introduced an extensive set of new electrical Data Cube modes that provide an entire force and electrical spectrum at every pixel.
We show how the combination of these two innovations enables a whole range of new electrical measurements in liquid, including in situ piezoelectric response, conductivity, Kelvin Probe mapping, and benefits for research in solar water splitting. We show data addressing applications ranging from Li-ion batteries, electrocatalysis, to semiconductors and bioelectricity.
Dr. Teddy Huang
Staff Development Applications Scientist, Bruker Nano Surfaces
Ph.D. student, University of Oregon