On-site electrochemical production of hydrogen peroxide (H₂O₂), an oxidant and disinfectant with growing demand, could be realized through the selective two-electron oxygen reduction reaction (2e^– ORR), but the widespread adoption of this method depends on robust and efficient electrocatalysts. Current catalysts have been limited by cost or toxicity and lack well-defined structures that can facilitate systematic tuning of activity and selectivity. Here, we demonstrate a series of CuCo_2–xNi_xS₄ (0 ≤ x ≤ 1.2) thiospinel catalysts for 2e^– ORR with variable compositions that can be synthesized via hydrothermal conversion. Rotating ring disk electrode measurements show that these catalysts have high selectivity for 2e^– ORR (>60%) and that their activity can be improved by increasing the nickel content without compromising selectivity. An acid treatment step is critical prior to employing the optimized CuCo_0.8Ni_1.2S₄ catalyst for bulk electrosynthesis of H₂O₂ in 0.05 M H₂SO₄ solution. Various structural analyses, including synchrotron X-ray spectroscopy, confirm that the catalysts retain the spinel structure after acid treatment and H₂O₂ electrosynthesis. The acid treatment likely leaches the soluble copper species from the as-synthesized catalysts that would catalyze an electro-Fenton process to consume H₂O₂, generate hydroxyl radicals, and therefore prevent the accumulation of H₂O₂. This work demonstrates a general strategy for systematic tuning of metal compound catalysts for practical H₂O₂ electrosynthesis and facile generation of hydroxyl radicals.

中文翻译：

---

用于增强过氧化氢电合成和内置羟基自由基生成的组成调节的三金属硫尖晶石催化剂

过氧化氢 (H ₂ O ₂ ) 是一种需求不断增长的氧化剂和消毒剂，可以通过选择性双电子氧还原反应 (2e ^– ORR)实现现场电化学生产，但这种方法的广泛采用取决于强大而高效的电催化剂。目前的催化剂受到成本或毒性的限制，并且缺乏可以促进活性和选择性系统调整的明确结构。在这里，我们展示了一系列用于 2e ^–的 CuCo _{2– x} Ni _x S ₄ (0 ≤ x ≤ 1.2) 硫尖晶石催化剂具有可变成分的 ORR，可通过水热转化合成。旋转环盘电极测量表明，这些催化剂对 2e ^– ORR (>60%)具有高选择性，并且可以通过增加镍含量而不影响选择性来提高其活性。在使用优化的 CuCo _0.8 Ni _1.2 S ₄催化剂在 0.05 MH ₂ SO ₄溶液中大量电合成 H ₂ O ₂之前，酸处理步骤是关键。各种结构分析，包括同步加速器 X 射线光谱，证实催化剂在酸处理和 H ₂ O后仍保留尖晶石结构₂电合成。酸处理可能会从合成催化剂中浸出可溶性铜物质，该催化剂将催化电芬顿过程消耗 H ₂ O ₂，产生羟基自由基，从而防止 H ₂ O ₂的积累。这项工作展示了系统调整金属化合物催化剂以用于实际 H ₂ O ₂电合成和轻松生成羟基自由基的一般策略。