Department of Chemistry, Tsinghua University, Beijing, 100084, China.
Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China.
Adv Mater. 2018 Apr;30(15):e1706508. doi: 10.1002/adma.201706508. Epub 2018 Mar 6.
A novel polymer encapsulation strategy to synthesize metal isolated-single-atomic-site (ISAS) catalysts supported by porous nitrogen-doped carbon nanospheres is reported. First, metal precursors are encapsulated in situ by polymers through polymerization; then, metal ISASs are created within the polymer-derived p-CN nanospheres by controlled pyrolysis at high temperature (200-900 °C). Transmission electron microscopy and N sorption results reveal this material to exhibit a nanospheric morphology, a high surface area (≈380 m g ), and a porous structure (with micropores and mesopores). Characterization by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure confirms the metal to be present as metal ISASs. This methodology is applicable to both noble and nonprecious metals (M-ISAS/p-CN, M = Co, Ni, Cu, Mn, Pd, etc.). In particular, the Co-ISAS/p-CN nanospheres obtained using this method show comparable (E = 0.838 V) electrochemical oxygen reduction activity to commercial Pt/C with 20 wt% Pt loading (E = 0.834 V) in alkaline media, superior methanol tolerance, and outstanding stability, even after 5000 cycles.
本文报道了一种新颖的聚合物封装策略，用于合成负载于多孔氮掺杂碳纳米球中的金属孤立单原子位点（ISAS）催化剂。首先，通过聚合反应将金属前驱体原位封装在聚合物中；然后，通过在高温（200-900°C）下进行可控热解，在聚合物衍生的 p-CN 纳米球内形成金属 ISAS。透射电子显微镜和氮气吸附结果表明，该材料具有纳米球形态、高比表面积（≈380 m²/g）和多孔结构（具有微孔和介孔）。通过像差校正高角环形暗场扫描透射电子显微镜和 X 射线吸收精细结构的表征证实，金属以金属 ISAS 的形式存在。该方法适用于贵金属和非贵金属（M-ISAS/p-CN，M = Co、Ni、Cu、Mn、Pd 等）。特别是，通过该方法获得的 Co-ISAS/p-CN 纳米球在碱性介质中表现出与商业 Pt/C（负载 20wt%Pt，E = 0.834 V）相当的电化学氧还原活性（E = 0.838 V），具有优异的甲醇耐受性和出色的稳定性，甚至在 5000 次循环后仍保持稳定。
