Impact Electrochemistry of Layered Transition Metal Dichalcogenides

Abstract

Layered transition metal dichalcogenides (TMDs) exhibit paramount importance in the electrocatalysis of the hydrogen evolution reaction. It is crucial to determine the size of the electrocatalytic particles as well as to establish their electrocatalytic activity, which occurs at the edges of these particles. Here, we show that individual TMD (MoS2, MoSe2, WS2, or WSe2; in general MX2) nanoparticles impacting an electrode surface provide well-defined current "spikes" in both the cathodic and anodic regions. These spikes originate from direct oxidation of the nanoparticles (from M(4+) to M(6+)) at the anodic region and from the electrocatalytic currents generated upon hydrogen evolution in the cathodic region. The positive correlation between the frequency of the impacts and the concentration of TMD nanoparticles is also demonstrated here, enabling determination of the concentration of TMD nanoparticles in colloidal form. In addition, the size of individual TMD nanoparticles can be evaluated using the charge passed during every spike. The capability of detecting both the "indirect" catalytic effect of an impacting TMD nanoparticle as well as "direct" oxidation indicates that the frequency of impacts in both the "indirect" and "direct" scenarios are comparable. This suggests that all TMD nanoparticles, which are electrochemically oxidizable (thus capable of donating electrons to electrodes), are also capable of catalyzing the hydrogen reduction reaction.

Nanorod Aspect Ratios Determined by the Nano‐Impact Technique

“…This method has been pioneered for spherical nanoparticles through nano‐impact experiments, where the electrochemical size determination of the materials has been established and verified alongside other methods. This approach relies upon the impact of individual nanoparticles with an electrode surface, where control of the applied potential leads to either the direct or indirect observation of the nanoparticles. While this method has shown remarkable success for the sizing of spherical or quasi‐spherical nanoparticles, its extension to determine the dimensions of non‐spherical geometries is unexplored, marking an exciting opportunity for growth in this field.…”

Ultra-high electrochemical catalytic activity of MXenes

“…Extensive efforts have been carried out to reduce the amounts of noble metals by alloying with cheap metals and tuning the composition of the catalysts789101112. Alternatively, novel electrocatalysts with low cost and rich abundance have been widely investigated to replace noble-metal catalysts1314151617181920212223242526272829303132333435. Especially, two-dimensional (2D) monolayers as electrocatalysts, such as 2D transition-metal dichalcogenides monolayers (TMDs), have been attracting increasing interests because of their unique physical and chemical properties20212223242526272829303132333435.…”

Electrochemical analysis of single particles

“…Bard等 [35] 对颗粒的碰撞频率进行了研究. 他们发 现, 若颗粒的吸附速率常数kads较大, 则最大碰撞频率 满足菲克(Fick)定律, 可根据式 (2) [32,33,37~43] , 该方法已被应用于其他种类材质的单颗粒 检测, 包括金属氧化物 [44] 、过渡金属二硫化物 [45] 等.…”