The SO₂-depolarized electrolysis (SDE) is a promising method for SO₂ capture and hydrogen production. But the SDE is limited by the high overpotential and slow kinetics of anodic SO₂ oxidation reaction (SOR). Herein, to boost SDE process, we add hydroiodic acid (HI) to the anolyte and form HI-assisted SO₂-depolarized electrolysis (HASDE). The mechanism of HI assisted SOR is explored, the existence of HI reduces the onset potential and impedance, but increases current density and reaction rate of SOR. HI is supposed to change the single-step SOR into three-step reactions, without changing the overall anodic reaction. A HI concentration of less than or equal to 0.02 mol/L and an operating temperature of 50 °C or less are recommendable. The comparison of SDE and HASDE processes indicates that HASDE delivers a lower cell voltage than SDE during continuous constant-current electrolysis, and has negligible effect on cathodic H₂ evolution, while it achieves 27.03–48.65% reduction in electric energy consumption compared with SDE. The present work provides an innovative strategy for improving SDE and energy-saving production of value-added chemicals like H₂SO₄ and H₂.

SO _2去极化电解（SDE）是一种有前途的SO ₂捕获和制氢方法。但是，SDE受阳极SO ₂氧化反应（SOR）的高过电势和慢动力学限制。在这里，为了促进SDE过程，我们将氢碘酸（HI）添加到阳极液中并形成HI辅助的SO ₂-去极化电解（HASDE）。探索了HI辅助SOR的机理，HI的存在降低了起始电位和阻抗，但增加了SOR的电流密度和反应速率。HI应该将单步SOR更改为三步反应，而不改变整个阳极反应。推荐HI浓度小于或等于0.02 mol / L，工作温度为50°C或更低。SDE和HASDE工艺的比较表明，在连续恒流电解期间，HASDE的电池电压低于SDE，并且对阴极H _2的影响可忽略不计与SDE相比，它的能耗降低了27.03–48.65％。目前的工作为提高SDE和节能生产H ₂ SO ₄和H ₂等高附加值化学品提供了创新的策略。