Contradictory role of reactive oxygen species in dissolution-dependent activity of Pb-based anodes in acidic electrooxidation†
*ab
Abstract
The dilemma of activity and stability limits the application of metal-based anodes in electrooxidation, especially in concentrated acid media, and thus causes the emission of hazardous wastewater and waste. Herein, a strong correlation is first reported between activity and Pb2+ dissolution of Pb-based anodes in acidic-electrooxidation. This complex relationship lies in the contradictory role of reactive oxygen species (ROS, SO4−* and OH*). Although the evolution of ROS is a crucial step for Pb passivation and oxygen evolution, the elimination of ROS results in exposure and dissolution of Pb2+. Moreover, oxygen evolution is hindered due to the mismatch of ROS energy bonding. Based on these discoveries, a simple, competitive and sustainable strategy is proposed for changing the ROS evolution environment by precoating MnO2 on Pb-based anodes. Pb-based MnO2 anodes (PMAs) with different ROS evolution environments present ultra-low Pb2+ dissolution (reduced by ∼95%) and enhanced oxygen evolution performance because of the uniform energy bonding distribution. These findings have conclusively confirmed ROS behaviour control as the criterion for alleviating dissolution-dependent activity of metal-based anodes for extensive electrooxidation.
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