高等学校化学学报 ›› 2018, Vol. 39 ›› Issue (5): 949-955.doi: 10.7503/cjcu20170720

• 物理化学 • 上一篇    下一篇

石墨烯负载Pt-Pd催化剂的制备、催化制氢性能及机理研究

鲁礼林1,2, 舒红飞2, 阮祝华2, 倪嘉琪2, 张海军1   

  1. 1. 武汉科技大学省部共建耐火材料与冶金国家重点实验室, 2. 化学与化工学院, 煤转化与新型炭材料湖北省重点实验室, 武汉 430081
  • 收稿日期:2017-11-10 出版日期:2018-04-10 发布日期:2018-04-10
  • 作者简介:

    联系人简介: 鲁礼林, 男, 博士, 副教授, 主要从事能源催化方面的研究. E-mail: lulilin@wust.edu.cn

  • 基金资助:
    国家自然科学基金(批准号: 21671154, U1732147)、 武汉科技大学省部共建耐火材料与冶金国家重点实验室青年基金(批准号: 2016QN06)和绿色制造与节能减排技术研究中心开放基金(批准号: B1206)资助.

Preparation of Graphene-supported Pt-Pd Catalyst and Its Catalytic Activity and Mechanism for Hydrogen Generation Reaction

LU Lilin1,2,*, SHU Hongfei2, RUAN Zhuhua2, NI Jiaqi2, ZHANG Haijun1   

  1. 1. State Key Laboratory of Refractories and Metallurgy, 2. School of Chemistry and Chemical Engineering, Hubei Province Key Laboratory of Coal Conversion and New Carbon Materials, Wuhan University of Science and Technology, Wuhan 430081, China
  • Received:2017-11-10 Online:2018-04-10 Published:2018-04-10
  • Contact: LU Lilin
  • Supported by:
    † Supported by the National Natural Science Foundation of China(Nos.21671154, U1732147), the Youth Fund of State Key Laboratory of Refractories and Metallurgy, China(No.2016QN06) and the Open Fund of Research Center of Green Manufacturing and Energy-saving and Emission Reduction Technology, China(No.B1206).

摘要:

以氧化石墨烯为载体, 采用乙醇共还原法制备了石墨烯负载Pt-Pd双金属纳米催化剂, 并将其用于催化碱性硼氢化钾(KBH4)水解制氢研究. 采用X射线衍射(XRD)分析和透射电子显微镜(TEM)等手段表征了催化剂的微观形貌和结构, 发现当金属催化剂中Pt/Pd摩尔比为1∶1时, Pt-Pd双金属催化剂颗粒可均匀地负载于石墨烯载体表面, 而且粒径比单金属催化剂和其它组成的双金属催化剂粒径更小, 约为5.6 nm. 将该催化剂用于催化碱性条件下KBH4水解制氢实验, 结果表明, 金属催化剂的化学组成对其催化性能有明显影响, 当Pt/Pd摩尔比为1∶1时其催化活性高于其它化学组成(Pt/Pd摩尔比为4∶1或1∶4)的Pt-Pd双金属催化剂, 催化活性可达4380 molH2·molM-1·h-1, 比Pt单金属催化剂活性提高约52%, 为Pd单金属催化剂活性的4倍. 通过催化反应动力学研究发现, Pt-Pd双金属催化剂催化KBH4水解制氢反应的活化能约为20.90 kJ/mol, 催化剂具有较佳的耐久性, 连续使用3次后催化效率仍可达首次催化反应效率的83%. 利用密度泛函理论研究了催化剂催化KBH4水解反应的机制, 发现双金属纳米催化剂可以明显降低硼氢化物水解反应决速步骤基元反应的势垒, 从而显著提高催化剂的催化活性.

关键词: 催化制氢, Pt-Pd双金属催化剂, 硼氢化钾, 反应机理

Abstract:

The graphene-supported nano Pt-Pd bimetallic catalysts with various chemical compositions(Pt/Pd molar ratio: 4∶1, 1∶1, 1∶4) were prepared via simple ethanol reduction method by reflux of graphene oxide(GO) and metallic salts in ethanol/water solvent for 5.5 h at 88 ℃. For comparison, graphene-supported Pt, Pd monometallic catalysts were also synthesized under the same experimental conditions. The morphology of as-prepared catalysts was characterized by XRD and TEM, the results indicate that chemical composition of metallic catalysts shows distinct influence on the particle morphology and size, the Pt-Pd bimetallic catalyst particles disperse on the surface of graphene support most evenly with the average diameter of approximately 5.6 nm when the Pt/Pd molar ratio was set as 1∶1. Their catalytic activities for hydrolysis reaction of alkaline potassium borohydride(pH=12.0) were investigated, the catalytic experiment results demonstrate that the catalytic activities significantly depend on chemical composition of metallic catalyst, among them the Pt-Pd bimetallic catalyst with the molar ratio of 1∶1 displays higher activity than other Pt-Pd bimetallic catalysts(Pt/Pd molar ratios of 1∶4 and 4∶1) and Pt, Pd monometallic catalysts, the hydrogen generation efficiency of graphene-supported nano Pt-Pd(molar ratio 1∶1) bimetallic catalysts is about 4380 molH2·molM-1·h-1, which is higher than graphene-supported Pt catalyst by 52% and approximately as four-fold as graphene-supported Pd catalyst. Investigation on the catalytic durability demonstrated that about 83% of the initial catalytic activity was retained even after three cycles. Catalytic reaction kinetics studies manifest the activation energy of borohydride hydrolysis reaction catalyzed by graphene supported Pt/Pd(molar ratio 1∶1) bimetallic catalyst is about 20.90 kJ/mol, which is distinctly lower than those of the reaction catalyzed by Pt/C and Ru/C catalysts. DFT calculations based on M55 model revealed that the barrier height of rate-determining step catalyzed by Pt25Pd30 are distinctly lower than that catalyzed by Pd55 and Pt55, indicating the graphene supported Pt-Pd(Pt/Pd molar ratio 1∶1) possess more excellent catalytic activity.

Key words: Catalytic hydrogen generation, Pt-Pd bimetallic catalyst, Potassium borohydride, Reaction mechanism

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