Boron‐Doped Diamond for Hydroxyl Radical and Sulfate Radical Anion Electrogeneration, Transformation, and Voltage‐Free Sustainable Oxidation

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2019-11, Vol.15 (48), p.e1900153-n/a
• Main Authors: Cai, Junzhuo, Niu, Tiezheng, Shi, Penghui, Zhao, Guohua
• Format: Article
• Language: English
• Subjects: Boron; boron‐doped diamond; Contaminants; contaminates removal; Degradation; Diamonds; Electron paramagnetic resonance; Energy consumption; hydroxyl radical; Hydroxyl radicals; Nanotechnology; Oxidation; Power consumption; Power supplies; Power supply; Restoration; sulfate radical anion; sustainable oxidation; Transformations
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.201900153

Boron‐doped diamond‐based electrochemical advanced oxidation processes (BDD‐EAOPs) have attracted much attention. However, few systematic studies concerning the radical mechanism in BDD‐EAOPs have been published. In situ electron paramagnetic resonance spectrometry is used to confirm that SO4•− is directly electrogenerated from SO42−. Then, excess SO4•− dimerizes to form S2O82− and accumulates in the BDD‐EAOP system. But no S2O82− accumulates at pH = 10 owing to the rapid transformation of SO4•− and S2O82−. Above the overpotential of water oxidation, •OH is electrogenerated and cooperated with SO4•−. In the power‐off phase, the accumulated S2O82− can be reactivated to SO4•− via specific degradation intermediates to achieve sustainable degradation. Di‐n‐butyl phthalate (DnBP), a typical endocrine disruptor, is selected as a model contaminant. Surprisingly, 99.8% of DnBP (initial concentration of 1 mg L−1) is removed, using an intermittent power supply strategy with a periodic 10 min power‐on phase at a duty ratio of 1:2, reducing the electrical energy consumption (1.8 kWh m−3) by more than 30% compared with continuous power supply consumption. These radical electrogeneration transformation mechanisms reveal an important new strategy for sustainable oxidation, especially for in situ water restoration, and are expected to provide a theoretical basis for BDD applications. Novel insight concerning the radical mechanism at a boron‐doped diamond (BDD) anode is obtained, given by a series of advanced methods including in situ electrochemical electron paramagnetic resonance (EPR) spectroscopy. An important strategy for sustainable oxidation, in particular for in situ water remediation, is revealed. This strategy provides new theoretic evidence and will expand environmental applications of boron‐doped diamond materials.