A combination of different atomic force microscopy (AFM) techniques able to draw structure-function correlations to optimize photoelectrochemical assemblies under operating conditions (e. g. in liquid, under applied bias and illumination).
This suite of characterization techniques comprises peak force AFM (PF-AFM), photoconductive AFM (PC-AFM), kelvin probe force microscopy (KPFM), electrochemical AFM (EC-AFM), and photoelectrochemical AFM (PEC-AFM), for in-situ and operando characterizations of PEC materials and devices. A central aspect of this capability is focused on probing nanoscale properties of photoelectrocatalytic materials under illumination. Nanoscale characterization of photocatalysts in their working environments will enable understanding of reaction mechanisms and pave the way to rational design of efficient and selective heterogeneous photocatalysts of importance in a broad range of applications.
PF-AFM: This technique features direct, precise force control of the AFM measurements, and eliminates damaging lateral forces, thereby enabling high sensitivity and high-resolution current imaging. This is a basic tool that we can employ with all the following capabilities.
PC-AFM: Homogeneity of local conductive properties of photoelectrochemical assemblies can be investigated by PC-AFM, which simultaneously provides very high spatial resolution (~20 nm) for topology and photocurrent. We can offer full control on measurements conditions such as humidity, oxygen level, wavelength and light intensity with sub- and above band gap illumination. We found all these parameters to affect photo-carrier transport and trapping/de-trapping of defect states.
KPFM: Similar to the previous technique we can probe materials heterogeneity by correlating surface potential of photoelectrochemical assemblies with nanoscale morphology. We can control humidity, oxygen level, wavelength and light intensity with sub- and above band gap illumination. Specifically, we can achieve high spatial resolution by utilizing frequency modulated KPFM (FM-KPFM).
EC-AFM: This technique enables the time-lapse topological observation of photoelectrocatalytic and electrocatalytic materials under in situ and operando conditions with very high (<10 nm) spatial resolution.
PEC-AFM: This scanning probe technique will combine scanning electrochemical microscopy (SECM) with photoconductive atomic force microscopy (PC-AFM) for in situ and operando study of heterogeneous photocatalytic reactions at the nanoscale. We can measure contact current and photoelectrochemical current in different environment and under different illumination conditions, and correlate this information to topography. The resolution of this technique is currently <100 nm.