The Microstructure–Activity Relationship of Metal–Organic Framework-Based Electrocatalysts for the Oxygen Evolution Reaction at the Single-Particle Level

Abstract

Metal−organic framework (MOF)-based materials have garnered attention as promising candidates for electrocatalytic oxygen evolution reactions (OER). However, it remains a challenge to understanding the structure−activity relationship of these materials at the single-particle level due to the limited resolution of characterizations. Here, we present an efficient approach that combines a singleparticle-at-the-tip technique with scanning electrochemical cell microscopy to reveal a relationship between the microstructure and electrochemical activity for sheet-like nickel-based MOF particles. We find a negative correlation between the sheet thickness and the OER activity based on statistical data at the single-particle level. The origin of the enhanced OER activity can be rationalized by the larger fraction of the (001) facet. Simultaneously, the derivation process of catalysts is documented to ensure the accuracy of structural information. This study enables a simple single-entity electrochemical strategy to understand the microstructure−activity relationship of MOF-based catalysts (MOF-C) and offers new insights into the design of high-performance MOF-C.

Single Entity Electrocatalysis

“…Liu et al combined the single-particle-atthe-tip approach with SECCM for the analysis of OER at 2D MOF particles (∼50−800 nm in thickness comprised of nickel atoms and two conductive ligands). 553 Here, the authors demonstrated a negative correlation between OER activity and MOF particle thickness, which they correlated to a higher ratio of the (001) facet at lower thicknesses. Peng et al used SECCM to analyze individual single-crystalline iron-substituted cobalt hydroxide nanoplates, where they were able to improve the inherent OER activity of basal planes by increased Fe incorporation and demonstrate higher intrinsic catalytic activity at edge sites of pristine cobalt hydroxide plates.…”

“…The measured activities, and resulting maps, were correlated to HRTEM images to reveal the enhanced activity of hematite rods correlated to increased presence of (001) facets (at the body of the rods). Liu et al combined the single-particle-at-the-tip approach with SECCM for the analysis of OER at 2D MOF particles (∼50–800 nm in thickness comprised of nickel atoms and two conductive ligands) . Here, the authors demonstrated a negative correlation between OER activity and MOF particle thickness, which they correlated to a higher ratio of the (001) facet at lower thicknesses.…”

Combination of Rapid Intrinsic Activity Measurements and Machine Learning as a Screening Approach for Multicomponent Electrocatalysts

“…The MA particles used in this study were synthesized via nanodroplet-mediated electrodeposition, as previously described. , First, the CNCE support substrate was prepared using our previously reported methods, and its physicochemical properties were examined. ,, Atomic force microscopy (AFM) revealed that the CNCE possessed surfaces with nanoscale flatness (Figure b). The CNCE surface reached a surface roughness of only ∼1.5 nm, in contrast to the carbon fiber electrode (CFE) and glass carbon electrode (GCE), which had height variations >5 nm (Figure c).…”

Recent Developments in Single-Entity Electrochemistry

“…When this approach was extended to the nucleation of single nanobubbles, the modulation of nanobubbles in ionic liquids was examined. , These advances provide valuable insights into the dynamics and mechanisms of nanoparticle and nanobubble nucleation relevant to electrocatalysis. Furthermore, building on early works that demonstrated the voltammetric electrocatalytic investigation of single nanoparticles immobilized on nanoelectrodes, , recent reports have correlated electrocatalytic activity with structural features of single-entity electromaterials. − Bimetallic nanoparticles and nickel-based metal–organic framework particles were studied for formic acid oxidation and oxygen evolution reaction (OER), respectively, demonstrating dependencies of electrocatalytic activity and turnover frequency on particle size, sheet thickness, elemental composition, and fractional coverage. Notably, structure–property investigation of these kinds would be daunting with ensemble measurements due to the lack of accessible synthetic techniques to make monodisperse nanoparticle samples.…”