Nanoscale Reactivity Mapping of a Single-Crystal Boron-Doped Diamond Particle

Abstract

Boron-doped diamond (BDD) is most often grown by chemical vapor deposition (CVD) in polycrystalline form, where the electrochemical response is averaged over the whole surface. Deconvoluting the impact of crystal orientation, surface termination, and boron-doped concentration on the electrochemical response is extremely challenging. To tackle this problem, we use CVD to grow isolated single-crystal microparticles of BDD with the crystal facets (100, square-shaped) and (111, triangle-shaped) exposed and combine with hopping mode scanning electrochemical cell microscopy (HM-SECCM) for electrochemical interrogation of the individual crystal faces (planar and nonplanar). Measurements are made on both hydrogen- (H-) and oxygen (O-)-terminated single-crystal facets with two different redox mediators, [Ru­(NH3)6]3+/2+ and Fe­(CN)6 4–/3–. Extraction of the half-wave potential from linear sweep and cyclic voltammetric experiments at all measurement (pixel) points shows unequivocally that electron transfer is faster at the H-terminated (111) surface than at the H-terminated (100) face, attributed to boron dopant differences. The most dramatic differences were seen for [Ru­(NH3)6]3+/2+ when comparing the O-terminated (100) surface to the H-terminated (100) face. Removal of the H-surface conductivity layer and a potential-dependent density of states were thought to be responsible for the behavior observed. Finally, a bimodal distribution in the electrochemical activity on the as-grown H-terminated polycrystalline BDD electrode is attributed to the dominance of differently doped (100) and (111) facets in the material.

Characterization of the Depth of Discharge-Dependent Charge Transfer Resistance of a Single LiFePO4 Particle

“…Scanning electrochemical cell microscopy (SECCM), which uses a micro/nanopipette as a probe, is an effective tool for visualizing sample surface reactivity as a faradic current 2D image. − SECCM was used to characterize the charge/discharge of the composite cathode electrode, the metal oxide coated thin-film cathode electrode, and the thin-film anode electrode . SECCM is an effective tool that visualizes the nanoscale charge/discharge property and characterizes the heterogeneity of the individual active material’s charge/discharge property for LIBs.…”

Scanning electrochemical cell microscopy for the study of (nano)particle electrochemistry: From the sub‐particle to ensemble level

“…The electrochemical activity of isolated single‐crystal boron‐doped diamond (BDD) microparticles (width ≈ 3–10 μm, height ≈ 5–7 μm) toward two outer‐sphere redox processes, [Ru(NH 3 ) 6 ] 3+/2+ and [Fe(CN) 6 ] 4−/3− , was recently reported. [ 51 ] Through spatially‐resolved i − E measurements, it was unequivocally shown that for H‐terminated BDD, the triangle‐shaped $$\{ {111} \}$$ facets support more rapid ET kinetics than the square‐shaped $$\{ {100} \}$$ facets, attributed to the higher boron dopant density (i.e., more metal‐like character) of the former. Changing from H‐termination to O‐termination significantly impacted the electrochemical response of the BDD.…”

Recent Advances in the Glass Pipet: from Fundament to Applications

“…SECCM is particularly attractive for nanoparticle and nanosheet studies, whereby the electrocatalytic activity of individual nanoparticles or nanosheets within an ensemble can be measured and correlated with the structure or morphology obtained from colocated complementary surface analysis. 121 Choi et al 122 measured HER of single Au nanoparticles expressing predominantly {100} or {111} crystal planes on the surface by using SECCM (Figure 6A). They found that Au 100 nanoparticles have superior HER electrocatalytic activity compared to that of Au 111 nanoparticles.…”