材料期刊网

用线性电位扫描、循环伏安、计时电量及电位衰减等电化学方法，研究了铟在3mol/L KOH溶液中的阳极饨化过程。铟在强碱性溶液中表现为一种活化一饨化金属。在活化区铟发生两步氧化，首先一电子氧化形成[InOH]ad，接着[InOH]ad二电子氧化成[In（OH）3]ad较低电位下前者较快后者较慢，表现为一电子反应；较高电位下两者均较快，表现为三电子反应，两者均受扩散步骤控制。单层[In（OH）3]ad形成后使铟进入饨化区。[In（OH）3]ad不稳定，在碱液中可以溶解和转变为In2O3。在饨化区，铟直接氧化成三价铟，较高电位下形成稳定的In2O3，较低电位下形成非化学计量的三价铟氧化物，其稳定性介于[In（OH）3]ad和In2O3之间。

The anodic passivation processes of indium in 3mol/L KOH solutions are investigated by using linear potential sweep,cyclic voltammetry,chronocoulometry and chronopotentiometry.Indium behaves as an active-passive metal in cincentrated alkaline solution.The oxidation processes of indium procees by two steps at active region, forming [InOH]ad from In and [In(OH)3]ad from [Inoh]ad.At lower potential,the formation of [InOH]ad is fast but the formation of [In(OH)3]ad is slow, so the reaction behaves as one electron transfer.At higher potential,both formations of [InOH]ad and [In(OH)3ad are fast,so the reaction behaves as three electron transfer,Two kinds of the reactions at active region are controlled by mass transport step.With the formation of monolayer [In(OH)3]ad, indium goes into the passive region.[In(OH)3]ad is not stable.Tr can dissolve into the solution and be transformed into more stable In2O3.Indium is oxidized directly to trivalent indium at the passive region.Within the passive region,the oxidation product is stable In2O3 at higher potential,and nonstoichiometric In2O3 which is more stable than [In(OH)3]ad bur less than In2O3 at lower potential.