Energy-Efficient Electrochemical Degradation of Organic Pollutants by Three-Dimensional Anode Packed with C/Sn–Sb Composite Particles

The industrial application of a conventional two-dimensional (2D) anode oxidation system is greatly limited by the low diffusion efficiency, high energy consumption, and high capital expense. In this study, a carbon/tin–antimony (C/Sn–Sb) composite was synthesized via a one-step pyrolysis process and used as the reactive particles to construct a three-dimensional (3D) anode system toward the degradation of organic pollutants. The doping Sn–Sb could increase the oxygen evolution potential (OEP) from 1.1 to 1.4 V/saturated calomel electrode (SCE), and the calculated electrochemical active surface area (ECSA) of C/Sn–Sb composite particles was as high as 444.8 cm2. Under optimal conditions (current density of 5 mA cm–2, hydraulic retention time (HRT) of 3.5 min, and particle filling volume of 75 g L–1), the phenol degradation efficiency reached 74% within 120 min with an energy consumption of only 0.0155 kWh g–1 chemical oxygen demand (COD), less than half that of its two-dimensional system. Noticeably, the performance of C/Sn–Sb composite particles in the three-dimensional anode system exhibited little dependence on solution pH in the range of 4–10. After five cyclic experiments, the COD and phenol degradation efficiency of the C/Sn–Sb particulate electrodes decreased by only 9 and 11%, demonstrating high catalytic stability. Although the particle electrode was gradually consumed during the electrolysis process, the straightforward, one-step synthesis protocol and low material costs enable convenient anode replenishment without significant operational interruptions. It was also demonstrated that the C/Sn–Sb composite particles predominantly mediated organic pollutant oxidation through indirect pathways. Generally, the particle anode system demonstrates superior mass transfer efficiency and low energy consumption. This study offers a feasible solution for organic wastewater treatment and provides an opportunity to promote the industrial application of particle electrodes.