Electrochemical oxidation based on SO4 •– and •OH generated from sulfate electrolyte is a cost-effective method for degradation of persistent organic pollutants (POPs). However, sulfate activation remains a great challenge due to lack of active and robust electrodes. Herein, a B/N codoped diamond (BND) electrode is designed for electrochemical degradation of POPs via sulfate activation. It is efficient and stable for perfluorooctanoic acid (PFOA) oxidation with first-order kinetic constants of 2.4 h–1 and total organic carbon removal efficiency of 77.4% (3 h) at relatively low current density of 4 mA cm–2. The good activity of BND mainly originates from a B and N codoping effect. The PFOA oxidation rate at sulfate electrolyte is significantly enhanced (2.3–3.4 times) compared with those at nitrate and perchlorate electrolytes. At sulfate, PFOA oxidation rate decreases slightly in the presence of •OH quencher while it declines significantly with SO4 •– and •OH quenchers, indicate both SO4 •– and •OH contribute to PFOA oxidation but SO4 •– contribution is more significant. On the basis of intermediates analysis, a proposed mechanism for PFOA degradation is that PFOA is oxidized to shorter chain perfluorocarboxylic acids gradually by SO4 •– and •OH until it is mineralized.

Co/Mn-MOFs-1-1-150, a two-dimensional sheet-like bimetallic Co/Mn-based MOF with peroxidase-like activity, efficiently accelerates the oxidation of TMB in the presence H2O2.

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Graphitic carbon nitride (g-C3N4) as a metal-free nanozyme has attracted huge attention for catalytic applications. However, the catalytic activity of pure g-C3N4 causes very moderate H2O2 activation. Herein, a novel three-dimensional (3D) branched carbon nitride nanoneedle (3DBC-C3N4) nanozyme has been proposed to overcome such shortcoming. This unique 3D branched structure of 3DBC-C3N4 facilitated effective mass transfer during catalytic reaction and induced a lightning rodlike effect to accelerate electron collection at the tip area for H2O2 activation. With improved H2O2 activation for hydroxyl radical (•OH) generation, 3DBC-C3N4 showed excellent peroxidase-like activity toward 3,3′,5,5′-tetramethylbenzidine oxidation in the presence of H2O2. As for H2O2, the V max value of 3DBC-C3N4 was found to be 20 times higher than that of natural horseradish peroxidase. Moreover, the 3D branched structure of 3DBC-C3N4 offered large interface for the reversible conjugation of single-stranded DNA, which enhanced the colorimetric sensitivity. Moreover, 3DBC-C3N4 exhibited high sensitivity toward oxytetracycline detection, with the detection limit and quantitative limit of 1 and 50 μg/L, respectively.