Photon-induced synthesis of ultrafine metal nanoparticles on graphene as electrocatalysts: impact of functionalization and doping
Photon-induced synthesis of ultrafine metal nanoparticles on graphene as electrocatalysts: impact of functionalization and doping
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DOI：
10.1039/c9ta10518b
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发表时间：
2020-01-14
影响因子：
11.9
通讯作者：
Baidak, Aliaksandr
中科院分区：
文献类型：
--
作者：
Guo, Kun;Rowland, Laura J.;Baidak, Aliaksandr
利用高能光子产生的还原物提供了一种在没有外源还原剂的情况下制备金属纳米颗粒（NPs）的替代策略。然而，对NP大小和分散性的精细控制仍然是一个很大的挑战。本文报道了通过选择合适的溶剂、前驱体浓度和碳载体，通过放射性分解法制备了均匀分布在氮掺杂石墨烯（NG）上的平均尺寸为3.0 nm的超细钯（Pd） NPs。对照实验表明，具有中等还原性的乙二醇是水的优良溶剂。在四种不同功能化或掺杂的石墨烯基载体中，氮掺杂剂在锚定NPs和控制其尺寸和分散性方面优于氧官能团。Pd/NG还为析氢反应（HER）提供了最低的eta(10)（电流密度为10 mA cm（-2）时的过电位）。Pd/NG与不同Pd负载的比较表明，当负载增加到2.6 wt%时，HER活性几乎达到平台，这受到NG含氮量的限制。x射线光电子能谱明确地揭示了电子从富电子的Pd转移到缺电子的氮，特别是石墨氮，证实了掺杂氮对稳定NG上Pd NPs的决定性作用。将这种合成扩展到铂（Pt），得到的Pt/NG比商用的10 wt% Pt/炭黑具有更低的eta(10)，因为NP尺寸更小。这些结果共同强调了高能光子在绿色、通用和可扩展的非均质纳米结构合成方面的潜力。
Utilizing reducing species generated by high-energy photons offers an alternative strategy to prepare metal nanoparticles (NPs) in the absence of a foreign reductant. However, fine control of the NP size and dispersity remains a big challenge. Herein, we report that by properly selecting the solvent, precursor concentration and carbon support, ultrafine palladium (Pd) NPs with an average size of 3.0 nm uniformly distributed on nitrogen-doped graphene (NG) are radiolytically prepared. Control experiments demonstrate that ethylene glycol with moderate reducibility is a superior solvent to water. Among four graphene-based supports with distinct functionalization or doping, nitrogen dopants outperform oxygen functional groups in anchoring the NPs and controlling their size and dispersity. Pd/NG also affords the lowest eta(10) (overpotential at a current density of 10 mA cm(-2)) toward the hydrogen evolution reaction (HER). Comparison of Pd/NG with varied Pd loadings indicates that the HER activity nearly reaches a plateau once the loading increases to 2.6 wt%, which is limited by the nitrogen content of NG. X-ray photoelectron spectroscopy unambiguously reveals the electron transfer from electron-rich Pd to electron-deficient nitrogen, especially graphitic nitrogen, corroborating the decisive role of doped nitrogen in stabilizing the Pd NPs on NG. Extending this synthesis to platinum (Pt) yields Pt/NG that presents even lower eta(10) than the commercial 10 wt% Pt/carbon black due to the smaller NP size. These results collectively highlight the potential of high-energy photons for green, versatile and scalable synthesis of heterogeneous nanostructures.