Facet dependence of electrocatalytic furfural hydrogenation on palladium nanocrystals  

电催化糠醛加氢反应中钯纳米晶的晶面效应

作　　者：Wenbiao Zhang Yanghao Shi Yang Yang Jingwen Tan Qingsheng Gao 张文彪;石杨豪;杨洋;谭静雯;高庆生(暨南大学化学与材料科学学院,功能超分子配合材料与应用广东省重点实验室,广东广州510632;华南理工大学制浆造纸工程国家重点实验室,广东广州510640)

机构地区：[1]College of Chemistry and Materials Science,and Guangdong Provincial Key Laboratory of Functional Supramolecular Coordination Materials and Applications,Jinan University,Guangzhou 510632,Guangdong,China [2]State Key Laboratory of Pulp and Paper Engineering,South China University of Technology,Guangzhou 510640,Guangdong,China

出　　处：《Chinese Journal of Catalysis》2022年第12期3116-3125,共10页催化学报（英文）

基　　金：国家自然科学基金(22175077);广东省自然科学基金(2021A1515012351);制浆造纸工程国家重点实验室开放基金资助项目(202114);广东省普通高校创新团队项目(2021KCXTD009).

摘　　要：Electrocatalytic hydrogenation(ECH)offers a sustainable route for the conversion of biomass-derived feedstocks under ambient conditions;however,an atomic-level understanding of the catalytic mechanism based on heterogeneous electrodes is lacking.To gain insights into the relation between electrocatalysis and the catalyst surface configuration,herein,the facet dependence of the ECH of furfural(FAL)is investigated on models of nanostructured Pd cubes,rhombic dodecahedrons,and octahedrons,which are predominantly enclosed by{100},{110},and{111}facets,respectively.The facet-dependent specific activity to afford furfuryl alcohol(FOL)follows the order of{111}>{100}>{110}.Experimental and theoretical kinetic analyses confirmed the occurrence of a competitive adsorption Langmuir-Hinshelwood mechanism on Pd,in which the ECH activity can be correlated with the difference between the binding energies of chemisorbed H(^(*)H)and FAL(^(*)FAL)based on density functional theoretical(DFT)calculations.Among the three facets,Pd{111}exhibiting the strongest^(*)H but the weakest^(*)FAL showed the copresence of the^(*)H and^(*)FAL intermediates on the Pd surface for subsequent hydrogenation,experimentally confirming its high ECH activity and Faradaic efficiency.The free energies determined using DFT calculations indicated that^(*)H addition to the carbonyl of FAL on Pd{111}was thermodynamically preferred over desorption to gaseous H2,contributing to efficient ECH to afford FOL at the expense of H2 evolution.The obtained insights into the facet-dependent ECH underline that surface bindings assist ECH or H2 evolution considering their competitiveness.These findings are expected to deepen the fundamental understanding of electrochemical refinery and broaden the scope of electrocatalyst exploration.电催化加氢反应能够在常温常压条件下,以可再生电能为驱动力、水为氢源,将生物质原料升级为高附加值化学品,避免了热催化中高温高压的反应条件,是近年来催化领域的研究热点.然而,如何深入理解电极多相界面上的催化机理仍存在诸多挑战.为了更好地理解电催化加氢和催化剂表面结构之间的构效关系,本文以三种钯基纳米晶为模型催化剂,系统研究了其在糠醛(FAL)电催化加氢反应中的晶面效应.三种Pd纳米晶体模型催化剂,即立方体(cubes)、菱形十二面体(RDs)和八面体(Octs),分别暴露了{100},{110}和{111}等特征晶面,特征晶面上确定的原子排列和电子结构为研究电催化加氢中的晶面效应,关联反应动力学与表面吸附态提供了便利.同时,为了确保电催化加氢活性与晶面真实结构之间可靠的关联性,首先使用电化学CO置换法去除了Pd纳米晶上残余的表面活性剂(卤素离子等),并通过循环伏安法的氧化还原峰证实特征活性晶面得以充分暴露.以生成产物糠醇的比活性为评价依据,Pd纳米晶在FAL电加氢中的活性遵循Octs>cubes>RDs的顺序,即晶面活性顺序为{111}>{100}>{110}.实验和理论动力学分析表明,在Pd表面电加氢反应符合基于竞争吸附模型的Langmuir-Hinshelwood加氢机制,其动力学特征与加氢反应速率和^(*)FAL与^(*)H结合能之间的差值(BEFAL-BEH)正相关.与Pd(100)和Pd(110)相比,Pd(111)得益于相对较强的吸附^(*)H能力和较弱的吸附^(*)FAL能力,表现了更高的晶面活性和糠醇得率,因为这两种吸附物在Pd(111)共存,有利于加氢反应的表面反应步骤,提高了加氢活性.从热力学角度分析,^(*)H在Pd(111)上更容易进攻FAL中的羰基,反应生成糠醇分子,而不是形成H_(2)脱附,这同样有利于提高电催化加氢效率.可见,^(*)H和^(*)FAL的表面吸附态是电催化加氢反应的关键因素,它们之间的竞争关系决定了加氢或析氢反应�

关 键 词：Electrocatalytic hydrogenation FURFURAL Pd nanocrystal Facet dependence Binding energy 

分 类 号：O626.11[理学—有机化学] O643.36[理学—化学]