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Synthesis of B-doped graphene quantum dots as a metal-free electrocatalyst for the oxygen reduction reaction
- Van Tam, Tran, Kang, Sung Gu, Babu, Kadumudi Firoz, Oh, Eun-Suok, Lee, Seung Geol, Choi, Won Mook
- Journal of materials chemistry A 2017 v.5 no.21 pp. 10537-10543
- boric acid, catalysts, catalytic activity, chemical bonding, electrical conductivity, electrochemistry, glucose, graphene, graphene oxide, hot water treatment, methanol, oxygen, quantum dots, temperature
- Boron-doped graphene quantum dots (BGQDs) have been synthesized by a one-step, facile and low temperature method through the hydrothermal treatment of glucose as the precursor in the presence of boric acid. The as-obtained BGQDs possess a high B-doping content up to 4.25% of uniform nm-size. Interestingly, the effect of different types of B–C bond species on the ORR catalytic activity has been investigated to clarify the origin of the electrochemical reduction of O₂. Further, the composite of the reduced graphene oxide (rGO) and BGQD (G-BGQDs) was also prepared as a metal-free electrocatalyst for the oxygen reduction reaction (ORR). The G-BGQD composites exhibit a significantly enhanced electrocatalytic activity, including a positive onset potential and a high current density with a one step, four-electron pathway toward the ORR, comparable to the commercial Pt/C catalyst. Among various B–C bond structures in BGQDs, the graphite-like BC₃ structure is considered to be an important site for the ORR by improving the electric conductivity and electrocatalytic activity of BGQDs, which is also confirmed by a DFT study. In addition, the G-BGQD composites show an outstanding long-term operational stability and high tolerance to the methanol crossover effect, which are comparable to the commercial Pt/C catalyst. These results demonstrate that the synthesized BGQD, as metal-free catalyst materials, may be inexpensive and efficient electrocatalysts for the replacement of Pt-based catalysts toward the ORR and other electrochemical applications.