Electrochemical Deposition Tailors the Catalytic Performance of MnO₂‐Based Micromotors

Abstract

Artificial micro/nanomotors that could perform diverse tasks autonomously at the micro/nanoscale have been emerging as promising tools in many practical applications. Electrochemical synthesis is one of the dominating methods to fabricate these micro/nanodevices with diverse geometries and material components. By changing the conditions of electrochemical deposition, the surface morphology, crystal structure, and hence the resultant performance of deposited material could be tailored. In the current work, a feasible fabrication strategy is presented in terms of three unique electrodeposition types (i.e., potentiodynamic, potentiostatic (PS), and galvanostatic) to synthesize different MnO2‐based micromotors. Distinct propulsion behavior as well as the catalytic degradation of azo‐dye organic waste (with methylene blue as the representative), between three kinds of MnO2‐based micromotors is clearly displayed, owing to the distinctive chemical composition and morphology designs. The activated R‐MnO2‐based micromotors in PS mode exhibit fast motion speed (up to 12 body length per second), leading to the highest degradation efficiency. Such propulsion performance is comparable with the microrockets made by noble metals such as Pt and Ag. The new protocol will have a profound impact on the design of synthetic micro/nanomotors and hold a considerable promise for their diverse applications.

Simultaneous Removal of Antibiotics and Heavy Metals with Poly(Aspartic Acid)‐Based Fenton Micromotors

“…OH radicals without catalysts and exhibits a bad oxidizing ability of TC alone. Nevertheless, in the presence of micromotors, the inner MnO 2 core not only decomposes H 2 O 2 to O 2 bubbles, which provides a recoil force for motion of micromotors, but also acts as a catalyst for the degradation of organic contaminants via Fenton‐like reaction [8d] . Meanwhile, there is a synergistic effect between the composite of Fe 2 O 3 and MnO 2 confirmed from our previous work [13] .…”

“…It has verified that Fe 2 O 3 NPs can be decorated by a unique electrochemical deposition method, to enhance the degradation efficiency through Fenton‐like reaction in neutral condition without light irradiation [13] . Furthermore, manganese oxide (MnO 2 ) becomes an attractive choice to replace noble metals and have shown marvelous waste decontamination efficacy [8d] . Because reactive oxygen species (ROS), especially oxidative hydroxyl radicals (OH), can be produced in Fenton‐like reaction by MnO 2 catalyzing H 2 O 2 , various organic pollutants which difficult to remove under natural environment are able to degrade completely [8d,13] .…”

“…Furthermore, manganese oxide (MnO 2 ) becomes an attractive choice to replace noble metals and have shown marvelous waste decontamination efficacy [8d] . Because reactive oxygen species (ROS), especially oxidative hydroxyl radicals (OH), can be produced in Fenton‐like reaction by MnO 2 catalyzing H 2 O 2 , various organic pollutants which difficult to remove under natural environment are able to degrade completely [8d,13] . Simultaneously, the autonomous motion of micromotor brings to a localized mixing effect and results in a fast degradation process.…”

Ultrafast Growth and Locomotion of Dandelion‐Like Microswarms with Tubular Micromotors

“…The average speed of the swarming is around 50 mm s −1 , which is 100× higher than that of conventional bubble‐propelled tubular micromotors. [ 8 ] Subsequently (45 and 75 ms later), the micromotor swarms repeat the instant locomotion and flash to different locations. Unlike the classical motion patterns for single MnO 2 tubular micromotor, [ 8 ] the swarming locomotion induced by ultrasound appears to be a zigzag mode with an unpredictable direction.…”

“…[ 8 ] Subsequently (45 and 75 ms later), the micromotor swarms repeat the instant locomotion and flash to different locations. Unlike the classical motion patterns for single MnO 2 tubular micromotor, [ 8 ] the swarming locomotion induced by ultrasound appears to be a zigzag mode with an unpredictable direction. The blurry configuration indicates the bubble floats up from the focused bottom wall and flashes around with the carried micromotor swarms.…”