Preparation and Electrocatalytic Oxygen Reduction Performance of Self-Doped Sludge-Derived Carbon

开发低成本、高性能的阴极催化剂是燃料电池商业化应用的关键. 本文以剩余污泥为前驱体，在碳化前通过连续添加苯酚来对污泥进行驯化，热解后得到自模板、自活化及N、P、Fe自掺杂的多孔类石墨烯碳材料. 结果表明，污泥经苯酚驯化后，微生物得到富集，含碳量显著提高，N、P、Fe等元素大大增加. 热解温度升高能提高材料的石墨化程度，但过高的温度会使杂原子掺杂量减少，从而降低氧还原催化活性. 其中，800 ℃下煅烧得到的污泥碳（PSC-800）比表面积为402.4 m2·g-1，远高于未驯化污泥碳（SC-800）的262.4 m2·g-1. 光电子能谱（XPS）数据表明，PSC-800具有较高的杂原子掺杂量及含铁量，形成了吡啶氮、石墨氮等氧还原活性位点. 在碱性条件下催化4电子的氧还原反应，初始电位为0.93 V，高于SC-800的0.89 V及其他温度煅烧的污泥碳（PSC-600：0.75 V，PSC-700：0.87 V， PSC-900：0.91 V）. 极限电流密度与商业铂碳相当，具有良好的稳定性及抗甲醇毒性.The development of low-cost, high-performance cathode catalysts is critical for practical application of fuel cells. Here, the N, P-doped porous graphene-like carbon with outstanding oxygen reduction reaction (ORR) performance was synthesized by pyrolysis of surplus sludge, which functioned as a self-doped, self-activated, and self-templated precursor by acclimation with continuous feedings of phenol. The results show that the amounts of microorganisms were enriched after acclimation, with increasing contents of N, P, Fe, as well as C atoms. The increasing pyrolysis temperature resulted in the formation of an ordered graphitic structure, however, the excessively high temperature induced the drop in the amounts of the heteroatoms that are doped in the carbon framework. The phenol-acclimated sludge pyrolyzed at 800 ℃(PSC-800) featured a BET surface area as high as 402.4 m2·g-1, which was much higher than that of the raw sludge carbon (SC-800) (262.4 m2·g-1). X-ray photoelectron spectroscopic (XPS) data suggests that the PSC-800 had higher levels of heteroatom doping, which was conductive to the formation of oxygen reduction active sites such as pyridinic nitrogen and graphitic nitrogen. The obtained PSC-800 exhibited excellent ORR activity in alkaline media with the onset potential of 0.93 V, higher than 0.75, 0.87, 0.91, and 0.89 V for PSC-600, PSC-700, PSC-900 and SC-800, respectively. In comparison to the commercial Pt/C catalyst, the PSC-800 showed comparable catalytic activity in terms of the close onset potential, kinetic-limiting current and four-electron transfer process, and higher tolerance to methanol toxicity and superior stability.国家自然科学基金项目（No. 21577041）资助作者联系地址：华南理工大学环境与能源学院，工业聚集区污染控制与生态修复教育部重点实验室， 广东 广州 510006Author's Address: School of Environment and Energy, the Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, South China University of Technology, Guangzhou 510006, China通讯作者E-mail：chfeng@scut.edu.c