Sensitive detection of persulfate by a novel self-powered electrochemical sensor with carbon cloth electrodes modified with tin-doped cobalt tetroxide

The accurate and rapid detection of persulfate concentration is important for environmental decontamination and human health protection. In this work, a novel self-powered electrochemical sensor for the sensitive monitoring of persulfate was developed, which utilized cobalt tetroxide (Co₃O₄@CC) or tin-doped cobalt tetroxide (Sn_xCo_3−xO₄@CC) cathode as the sensing element and anode with electrogenic microorganisms as the power supplier. The Co₃O₄@CC and Sn_xCo_3−xO₄@CC electrodes were fabricated by in situ growing nanostructured Co₃O₄ or Sn_xCo_3−xO₄ catalysts on carbon cloth. Electrochemical tests revealed that these electrodes exhibited excellent catalytic reduction performance toward persulfate because of the synergistic catalysis by Co₃O₄ and electrode electrons, well-exposed Co²⁺/Co³⁺ catalytic sites, and high electron transfer efficiency. Tin doping could enhance the catalytic persulfate reduction by improving the conductivity and electron transfer of the Co₃O₄ catalyst. The electrode prepared at a hydrothermal temperature of 90 °C and a tin dosage of 0.286 g·cm⁻² achieved the highest persulfate reduction activity under pH 7. The sensing properties of the self-powered sensors toward persulfate were explored in detail. Results showed that under the optimal external load of 300 Ω, the proposed sensor could display a broad detection range of 0 to 1500 μmol L⁻¹ K₂S₂O₈ with sensitivities of 1.13 and 0.12 μA μmol⁻¹ L, a detection limit of 1.11 μmol L⁻¹ (S/N = 3), and a fast response time within 30 s. The sensors also presented satisfactory reproducibility and selectivity during the detection of persulfate. The proposed sensor will provide a new approach for sensitive, on-site, and real-time monitoring of persulfate for a wide range of applications.