Real-Time Visualization of the Single-Nanoparticle Electrocatalytic Hydrogen Generation Process and Activity under Dark Field Microscopy

Visualizing
a chemical reaction process is critical for understanding
the mechanism of the reaction. For example, information on chemical
reactions involving single nanocatalysts has significant implications
for mechanism research and is vital for guiding the selection of the
most active nanocatalysts. In this work, dark field microscopy (DFM)
is utilized to observe the electrocatalytic reaction process of Au–Pt
core–shell nanoparticles (AuNPs@Pt) as an example. Hydrogen
ions were reduced to hydrogen (H2) on the surface of AuNPs@Pt
under a certain potential, forming H2 nanobubbles covering
the surface of AuNPs@Pt. As a result, the scattering intensity of
the nanomaterial was observed to significantly increase under DFM.
Therefore, the electrocatalytic reaction process could be monitored
in real time by simply observing the scattering intensity change via
DFM. Our investigation reveals a different nanobubble evolution process
with an average nucleation time and lifetime of 0.69 and 32.34 s,
respectively. Moreover, the catalytic activity between different nanomaterials
was studied. The relationship between the Pt shell thickness and the
average scattering intensity change reveals that the electrocatalytic
activity is closely related to the Pt content. Finally, from the brightness
of the scattering spot observed by DFM, the temporal and spatial distribution
information on the catalytic activity could also be obtained, which
is more abundant than the information obtained using the traditional
electrochemical method.