研究目的
To reveal the reaction dynamics of monolayer graphene in electrochemical oxidation and reduction processes with high spatiotemporal resolution, addressing questions about onset voltage, reaction speed, suppressibility, reversibility, and mechanisms.
研究成果
Electrochemical oxidation and reduction of graphene are rapid, reversible, and driven by free radicals from water electrolysis, with a 1.4 V onset voltage. Oxidation is spatially heterogeneous, defect-dependent, and self-limiting due to conductivity changes. Reduction is voltage- and pH-dependent, indicating a 1:1 proton-electron ratio. This enables controlled tuning of graphene derivatives.
研究不足
The study is limited to monolayer CVD graphene in specific electrolyte conditions; results may not generalize to other graphene forms or electrolytes. The self-limiting effect and heterogeneity might complicate uniform oxidation. Suppression with Co2+ was complicated by cobalt oxide deposits. Temporal and spatial resolutions, while high, are constrained by the IRM setup.
1：Experimental Design and Method Selection:
Integrated interference reflection microscopy (IRM) with electrochemistry to monitor graphene reaction dynamics. Used a two-electrode electrochemical system with graphene as the working electrode and an Ag/AgCl reference electrode. Applied varying oxidation and reduction voltages in cycles.
2：Sample Selection and Data Sources:
CVD-grown monolayer graphene deposited on glass coverslips, contacted with gold electrodes. Electrolyte was potassium phosphate buffer (pH=3 unless stated).
3：List of Experimental Equipment and Materials:
IRM microscope, gold electrodes, Ag/AgCl electrode, plastic well, potassium phosphate buffer, TEMPO (radical trap), Co2+ for suppression tests.
4：Experimental Procedures and Operational Workflow:
Applied voltage sequences (e.g., 1.4-1.7 V for oxidation, 0 V for reduction) for specific durations (e.g., 45 s oxidation, 120 s reduction). Recorded IRM images at 5 frames per second (200 ms temporal resolution) and electrochemical current. Performed multiple cycles with varying conditions.
5：4-7 V for oxidation, 0 V for reduction) for specific durations (e.g., 45 s oxidation, 120 s reduction). Recorded IRM images at 5 frames per second (200 ms temporal resolution) and electrochemical current. Performed multiple cycles with varying conditions.
Data Analysis Methods:
5. Data Analysis Methods: Converted IRM signal to oxidation degree linearly (I/I0 from 0.73 to 0.97 corresponding to 0% to 100% oxidation). Used micro-Raman spectroscopy, XPS, and electrical transport measurements for validation. Analyzed dependence on voltage, pH, and history.
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