基于原位红外光谱的水相苯酚电氧化机理研究

采用电化学原位红外光谱技术，研究了苯酚在Pt电极表面的电化学氧化机理。在0.1 mol/L Na₂SO₄溶液中，Pt电极上电化学氧化苯酚的反应电位为+0.9~1.0 V（vs SCE）、析氧电位为+1.3 V；电化学原位红外光谱结果表明，当电位<0.9 V时，苯酚氧化产物主要为苯二酚、醌及少量醇类物质；电位0.9~1.1 V时，苯环结构被破坏，氧化产物主要为酮、酸、醇和CO₂；根据官能团吸收峰的变化，苯酚在Pt电极表面氧化经历如下途径：苯酚→苯二酚→苯醌→酮、醇、酸→CO₂。同时研究了NH₄⁺对苯酚在Pt电极表面的电氧化的影响，结果表明在低电位区（<0.9 V）对苯酚氧化构成竞争。

Mechanism of phenol electro-oxidation in aqueous solution based on in situ infrared spectroscopy

The electrochemical oxidation mechanism of phenol on the surface of Pt electrode was studied by electrochemical in situ spectroscopy. In 0.1 mol/L Na₂SO₄ solution, the reaction potential of electrochemical oxidation of phenol on Pt electrode is +0.9—1.0 V (vs SCE), and the oxygen evolution potential is +1.3 V. In situ infrared spectroscopy showed that electrode potential had a great influence on oxidation behavior of phenol. When the potential was lower than 0.9 V, the main intermediates of phenol oxidation were dihydroxyhenzene, quinone and a few alcohols. When the potential was controlled between 0.9 V and 1.1 V, the structure of benzene ring was destroyed, and the main intermediates were ketones, acids, alcohols and CO₂. According to the changes in absorption peak of functional group, phenol oxidation on the platinum electrode surface was as follows: phenol, dihydroxyhenzene, quinone, ketone, alcohol, acid and CO₂. The potential of ammonia oxidation on the platinum electrode surface was + 0.5 V, which indicated that ammonia in competition with phenol oxidation in the low potential region (< 0.9 V).