The fundamental kinetics of the electrocatalytic sulfur reduction reaction (SRR), a complex 16-electron conversion process in lithium–sulfur batteries, is so far insufficiently explored. Here, by directly profiling the activation energies in the multistep SRR, we reveal that the initial reduction of sulfur to the soluble polysulfides is relatively easy owing to the low activation energy, whereas the subsequent conversion of the polysulfides into the insoluble Li₂S₂/Li₂S has a much higher activation energy, contributing to the accumulation of polysulfides and exacerbating the polysulfide shuttling effect. We use heteroatom-doped graphene as a model system to explore electrocatalytic SRR. We show that nitrogen and sulfur dual-doped graphene considerably reduces the activation energy to improve SRR kinetics. Density functional calculations confirm that the doping tunes the p-band centre of the active carbons for an optimal adsorption strength of intermediates and electroactivity. This study establishes electrocatalysis as a promising pathway to tackle the fundamental challenges facing lithium–sulfur batteries.

迄今为止，锂硫电池中复杂的16电子转化过程电催化硫还原反应（SRR）的基本动力学尚未得到充分研究。在这里，通过直接分析多步SRR中的活化能，我们发现，由于活化能低，将硫初步还原为可溶性多硫化物相对容易，而随后将多硫化物转化为不溶性Li ₂ S ₂ /李₂S具有更高的活化能，有助于多硫化物的积累并加剧多硫化物的穿梭作用。我们使用杂原子掺杂的石墨烯作为模型系统来探索电催化SRR。我们表明，氮和硫双掺杂石墨烯大大降低了活化能，以改善SRR动力学。密度泛函计算证实，掺杂可调节活性炭的p带中心，以获得最佳的中间体吸附强度和电活性。这项研究将电催化建立为解决锂硫电池面临的基本挑战的有前途的途径。