Probing Surface Electrochemical Activity of Nanomaterials using a Hybrid Atomic Force Microscope-Scanning Electrochemical Microscope (AFM-SECM)

Summary

Atomic force microscopy (AFM) combined with scanning electrochemical microscopy (SECM), namely, AFM-SECM, can be used to simultaneously acquire high-resolution topographical and electrochemical information on material surfaces at nanoscale. Such information is critical to understanding heterogeneous properties (e.g., reactivity, defects, and reaction sites) on local surfaces of nanomaterials, electrodes and biomaterials.

Abstract

Scanning electrochemical microscopy (SECM) is used to measure the local electrochemical behavior of liquid/solid, liquid/gas and liquid/liquid interfaces. Atomic force microscopy (AFM) is a versatile tool to characterize micro- and nanostructure in terms of topography and mechanical properties. However, conventional SECM or AFM provides limited laterally resolved information on electrical or electrochemical properties at nanoscale. For instance, the activity of a nanomaterial surface at crystal facet levels is difficult to resolve by conventional electrochemistry methods. This paper reports the application of a combination of AFM and SECM, namely, AFM-SECM, to probe nanoscale surface electrochemical activity while acquiring high-resolution topographical data. Such measurements are critical to understanding the relationship between nanostructure and reaction activity, which is relevant to a wide range of applications in material science, life science and chemical processes. The versatility of the combined AFM-SECM is demonstrated by mapping topographical and electrochemical properties of faceted nanoparticles (NPs) and nanobubbles (NBs), respectively. Compared to previously reported SECM imaging of nanostructures, this AFM-SECM enables quantitative assessment of local surface activity or reactivity with higher resolution of surface mapping.

Introduction

Characterization of electrochemical (EC) behavior can provide critical insights into the kinetics and mechanisms of interfacial reactions in diverse fields, such as biology^1,2, energy^3,4, material synthesis^5,6,7, and chemical process^8,9. Traditional EC measurements including electrochemical impedance spectroscopy¹⁰, electrochemical noise methods¹¹, galvan....

Protocol

1. Sample preparation

1. Preparation of faceted Cu₂O nanoparticles and deposition on silicon substrate
   1. Dissolve 0.175 g of CuCl₂∙2H₂O (99.9%) into 100 mL of deionized (DI) water to generate an aqueous solution of 10 mM CuCl₂.
   2. Add 10.0 mL of 2.0 M NaOH and 10 mL of 0.6 M ascorbic acid dropwise into the CuCl₂ solution.
   3. Heat the solution in a 250 mL round-bottom flask under constant stirring in a 55 °.......

Discussion

A combined AFM-SECM technique that enables high-resolution multimodal imaging has been described in this protocol. This technique allows for topography to be mapped simultaneously with the SECM current collected or mapped on single nanoparticles or nanobubbles. Experiments were performed using commercial probes. These probes were designed to provide chemical compatibility with a wide range of electrochemical environments, electrochemical performance, mechanical stability, and multiple-cycle handling¹⁸

Materials

Name	Company	Catalog Number	Comments
Equipment
Atomic force microsopy	Bruker, CA	Dimenison Icon
Bipotentiostat	CH Instruments, Inc.	CHI 700E
Materials
Silicon wafer	TED PELLA, Inc.	16013
Fresh gold plates	Bruker, CA	model 119-017-307
PF-SECM-AFM probes	Bruker, CA	990-050138
PF-SECM strain-release module	Bruker, CA	840-012-724
PF-SECM Probe Holder	Bruker, CA	900-050121
PF-SECM Chuck	Bruker, CA	PF-SECM Chuck
PF-SECM O-ring	Bruker, CA	598-000-106
PF-SECM cover glass, SECM Cell	Bruker, CA	900-050137
EC Cell Assy	Bruker, CA	932-017-300
ESD Field Service	Bruker, CA	490-000-066
PF-SECM Boot	Bruker, CA	900-050136
Spring connector block	Bruker, CA	900-050524
PFSECM Tweezers	Bruker, CA
Cable, SECM Tip module	Bruker, CA	468-050171
Ag wire	Bruker, CA	249-000-056
Pt wire	Bruker, CA	248-000-004
Hard sharp wire	Bruker, CA	TT-ECM10
Tubular ceramic membrane	Refracton	WFA0.1
Chemicals
Copper(II) chloride dihydrate	ACROS Organics	AC315281000
Sodium Hydroxide	Fisher Chemical	S318-100
Ascorbic Acid	Fisher Chemical	A61-25
Epoxy	Loctite	Instant Mix
Potassium Chloride	Fisher Chemical	P217-500
Hexaammineruthenium(III) chloride	ACROS Organics	AC363342500