Direct sustainable conversion of hydrogen sulfide (HS) enables collaborative recovery of H and S resources via a metal-enhanced microwave plasma strategy, avoiding the hydrogen waste in the traditional Claus process. However, the metal size effect on microwave plasma property, the optimal process parameters, and the enhancement mechanism remain unclear in HS conversion. Herein, the optimal tungsten needle (diameter: 1 mm, length: 60 mm, and tip angle: 10°) is experimentally proven for intensifying microwave discharge in multi-mode cavities. Theoretical calculations and plasma distribution reveal that the optimized tungsten needle achieves the ideal coupling with the microwave field, exhibiting extreme electric field augmentation around the needle tip. Tungsten-needle intensifies microwave-sustained plasma, realizing 40.2 % (90.1 %) conversion of 100 % (10 %) concentration HS to H at a low microwave power of 300 W with a good stability of 30 hrs. Low power, large flow rate, and high HS concentration are beneficial for improving energy efficiency. The excitation of microwave plasma is accompanied by a massive generation of highly energetic electrons. The direct high-energy electron-HS collision contributes a lot to HS splitting, especially for high-concentration HS. In-situ optical emission spectroscopy confirms the vital S and H radicals in the plasma. The free radical reactions triggered by electron collisions are responsible for the production of H and S. This work opens an avenue to sustainable and low-carbon hydrogen production from the direct conversion and utilization of HS.

中文翻译：

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钨针增强微波持续等离子体，加速 H2S 直接转化为 H2


硫化氢 (HS) 的直接可持续转化能够通过金属增强微波等离子体策略协同回收 H 和 S 资源，避免传统克劳斯工艺中的氢气浪费。然而，金属尺寸对微波等离子体性质的影响、最佳工艺参数以及HS转化的增强机制仍不清楚。在此，实验证明最佳钨针（直径：1 mm，长度：60 mm，尖端角度：10°）可增强多模腔中的微波放电。理论计算和等离子体分布表明，优化后的钨针实现了与微波场的理想耦合，在针尖周围表现出极端的电场增强。钨针增强微波持续等离子体，在 300 W 的低微波功率下实现 100 % (10 %) 浓度的 H2S 到 H 的 40.2 % (90.1 %) 转化，并具有 30 小时的良好稳定性。低功率、大流量、高H2S浓度有利于提高能源效率。微波等离子体的激发伴随着大量高能电子的产生。高能电子与 H2S 的直接碰撞对 H2S 分裂有很大贡献，特别是对于高浓度 H2S 而言。原位光学发射光谱证实了等离子体中重要的 S 和 H 自由基。电子碰撞引发的自由基反应负责产生H和S。这项工作为直接转化和利用H2S开辟了可持续、低碳氢气生产的途径。