掺硼金刚石膜电极表面产生羟基自由基的原位ESR研究

In situ ESR Study of Hydroxyl Radical Generation on a Boron Doped Diamond Film Electrode Surface

建立了原位电化学-电子顺磁共振(ESR)方法,系统研究了掺硼金刚石(BDD)膜电极表面在水溶液中的羟基自由基(·OH)产生规律.结果表明,在高于析氧电位时,·OH的生成速率随着阳极电位的升高、电流密度的增加而增大,增加速率逐渐减缓.与此同时,与氢终端的BDD膜电极相比,氧终端的BDD膜电极表面因具有较好的亲水性而具有更高的·OH产生能力.在电化学氧化处理有机废水的过程中,电极表面处于氧终端的状态,有利于·OH产生并保持较高的活性.溶液pH值也在一定程度上影响·OH生成反应,酸性溶液中,BDD膜电极表面的·OH产生能力强于在中性或碱性溶液中.进一步研究发现,BDD膜电极表面还可能生成O3-·0自由基.本研究为深入探索BDD膜电极表面·OH的产生机制提供了研究手段,为阐述BDD膜电极电极在污染物处理中高效性的本质提供了有效的证据.

An in situ electrochemistry-electron spin resonance（ESR） method was established to study the generation reaction and the variation regularity of hydroxyl radicals（·OH） on a boron doped diamond（BDD） film electrode in aqueous solution.Results indicate that,above the oxygen evolution potential of BDD film electrode（2.4 V in 0.5 mol· L-1 H2SO4 solution）,the generation rate of ·OH increases as the applied potential or current density increases.However,there was no·OH ESR response when the applied potential was below 2.4 V.Compared to H-terminated surface,the O-terminated surface has a higher·OH generation efficiency because it is hydrophilic and this favors the water splitting reaction.The degradation processes for organic pollutants are always operated under high potential or current density,which allow the BDD film electrode surface to maintain its O-terminated condition.These conditions favor the·OH generation reaction and the reaction takes place with high activity.The pH value of the solution also influenced the·OH generation reaction.BDD film electrode has a stronger·OH generation ability in an acidic medium than in a neutral or alkaline medium.We also found that O3-·0 can be produced on the surface of BDD film electrode.This article provides new insights into the mechanism of·OH generation on the surface of BDD film electrode and evidence of a highly efficient electrochemical oxidation process during the treatment of organic pollutants.