CeO2-Driven Cu/Cu2+ Redox Modulation Enhances the Faradaic Efficiency of Sodium Dithionite Synthesis from Sodium Bisulfite.

Although the electrochemical reduction method for synthesizing sodium dithionite (Na2S2O4) provides an environmentally friendly and mild route, its limited Faradaic efficiency at the electrode surface fails to meet the requirements for industrial application. Among the various catalysts explored, copper has exhibited notable catalytic activity toward the electroreduction of NaHSO3. However, the accumulation of the sulfite radical anion (SO2*-) on Cu electrode surfaces severely constrains the efficiency of Na2S2O4 electroproduction. In this work, copper nanoparticles as the primary active component was dispersed on a porous carbon foam, meanwhile, its electronic structure was modulated via introduced cerium with strong electron-withdrawing properties. In a bipolar membrane gap-flow electrolyzer, at a current of 210 mA, the cell voltage required to drive the electroreduction reaction over the Cu-Ce/NC electrode is only 1.53 V. The Cu-Ce/NC electrode achieves a faradaic efficiency as high as 96.7%, corresponding to a power consumption as low as 0.49 kWh·kg-1. Long-term stability tests demonstrate that the faradaic efficiency for the electrosynthesis of TDS over this electrode remains around 95% after 60 h of continuous operation. In situ Raman spectroscopy confirmed that cerium incorporation effectively suppresses the surface accumulation of SO2*- and accelerates the adsorption-conversion of HSO3-. This study offers a route for reducing the overpotential in NaHSO3 electroreduction and opens possibilities for the sustainable recycling of sulfur resources.