Surface Processes Control the Fate of Reactive Oxidants Generated by Electrochemical Activation of Hydrogen Peroxide on Stainless-Steel Electrodes

Low-cost stainless-steel electrodes can activate hydrogen peroxide (H2O2) by converting it into a hydroxyl radical (center dot OH) and other reactive oxidants. At an applied potential of +0.020 V, the stainless-steel electrode produced center dot OH with a yield that was over an order of magnitude higher than that reported for other systems that employ iron oxides as catalysts under circumneutral pH conditions. Decreasing the applied potential at pH 8 and 9 enhanced the rate of H2O2 loss by shifting the process to a reaction mechanism that resulted in the formation of an Fe(IV) species. Significant metal leaching was only observed under acidic pH conditions (i.e., at pH <6), with the release of dissolved Fe and Cr occurring as the thickness of the passivation layer decreased. Despite the relatively high yield of center dot OH production under circumneutral pH conditions, most of the oxidants were scavenged by the electrode surface when contaminant concentrations comparable to those expected in drinking water sources were tested. The stainless-steel electrode efficiently removed trace organic contaminants from an authentic surface water sample without contaminating the water with Fe and Cr. With further development, stainless-steel electrodes could provide a cost-effective alternative to other H2O2 activation processes, such as those by ultraviolet light.

Automated summary

Low-cost stainless-steel electrodes can efficiently activate hydrogen peroxide (H2O2) by producing hydroxyl radicals (•OH) and other oxidants. These electrodes demonstrate significantly higher •OH yield compared to iron oxide catalysts under circumneutral pH conditions. The stainless-steel electrodes effectively remove trace organic contaminants from water without leaching significant amounts of Fe and Cr. With further development, they could become a cost-effective alternative to other H2O2 activation processes like ultraviolet light.