A General Strategy to Synthesize Fluidic Single Atom Electrodes for Selective Reactive Oxygen Species Production.

Fine-tuning the geometric and electronic structure of catalytic metal centers via N-coordination engineering offers an effective design for the electrocatalytic transformation of O 2 to singlet oxygen ( 1 O 2 ). Herein, we develop a general coordination modulation strategy to synthesize fluidic single-atom electrodes for selective electrocatalytic activation of O 2 to 1 O 2 . Using a single Cr atom system as an example, >98% 1 O 2 selectivity can be achieved from electrocatalytic O 2 activation due to the subtle engineering of Cr-N 4 sites. Both theoretical simulations and experimental results determined that "end-on" adsorption of O 2 onto the Cr-N 4 sites lowers the overall activation energy barrier of O 2 and promotes the breakage of Cr-OOH bonds to form • OOH intermediates. In addition, the flow-through configuration ( k = 0.097 min -1 ) endowed convection-enhanced mass transport and improved charge transfer imparted by spatial confinement within the lamellar electrode structure compared to that of batch reactor ( k = 0.019 min -1 ). In a practical demonstration, the Cr-N 4 /MXene electrocatalytic system exhibits a high selectivity toward electron-rich micropollutants (e.g., sulfamethoxazole, bisphenol A, and sulfadimidine). The flow-through design of the fluidic electrode achieves a synergy with the molecular microenvironment that enables selective electrocatalytic 1 O 2 generation, which could be used in numerous ways, including the treatment of environmental pollution.