铜基LDH/rGO纳米片阵列结构的构建及其协同增强催化还原硝基酚性能

Design and fabrication of highly dispersed non-noble metal Cu-based catalyst for catalytic selective hydrogenation of nitrophenol hold important interest both in academic research and industrial application. The project aims at exploring highly dispersed non-noble metal copper-based hierarchical nanoplates array ternary copper-based layered double hydroxide/reduced graphene oxide hybrids (M=Mg, Ni, Co, Zn)Al-LDH/rGO catalysts and their proper calcined derivate catalysts by a one-step aqueous-phase citric acid assisted co-precipitation method. The morphology controllable CuMAl-LDH/rGO nanohybrids can be prepared by carefully tuning the synthesis parameters such as metal composition, molar ratio of Cu2+ to graphene oxide and the reaction kinetics such as low temperature and slow initial stirring rate, which is critical for subsequent growth of well-defined and monodispersed LDH nanoplates on rGO layers. Upon the reduction property of rGO, proper calcination are expected to in-situ reduce lattice-confined Cu2+ ions on LDH nanosheets to highly dispersed core-shell-like Cu@Cu2O nano-particles, which will be intimately attached to amorphous or poor- crystallized non-copper non precious metal oxides around rGO matrix leading to highly active and stable supported Cu-based catalyst. Combinational characterizations can be employed to study the compositions, size and electron structure of Cu-based nanohybrids catalysts and the effect of possible Cu - Cu2O nanoparticles - LDH - rGO synergy upon the model reaction of chemoselective reduction for nitrophenol. Based on deep structure analysis and experimental data, the key role of size effect of Cu-based nano-particles and Cu-LDH-rGO co-enhanced function of the novel graphene loaded and non-copper 3d metal oxides confined Cu-based nanocatalyst in chemoselective reduction of nitrophenol can be revealed and compared with possible catalytic mechanism and general regulation.

设计组装高分散非贵金属铜基纳米催化剂在化学选择性催化加氢领域具有重要的研究意义和潜在的应用价值。课题拟以一步水相柠檬酸助共沉淀法构建铜基三元水滑石/还原氧化石墨烯纳米片阵列结构CuM(M=Mg,Ni,Co,Zn)Al-LDH/rGO及其焙烧衍生rGO负载、非铜金属氧化物限域的类核壳铜基催化剂。精细调控合成参数，控制动力学过程制备形貌可控的CuMAl-LDH/rGO杂化物是关键；煅烧中控制合适条件可望将LDH层板中的晶格限域Cu2+离子经rGO原位还原为类核壳结构Cu@Cu2O纳米粒。系统表征杂化物及衍生催化剂的结构、形貌及组成，以水相4-硝基苯酚还原为模型，研究系列催化剂的催化加氢活性及循环稳定性。通过深入的结构研究和实验探索，从分子水平理解铜基催化剂的催化性能并确定铜及非铜3d金属的结构形态、价态、相互作用及其与rGO的协同增强效应，揭示催化剂的构效关系，寻找普适性规律。

设计合成高分散非贵金属铜基纳米催化剂在化学选择性催化加氢领域具有重要的研究意义和潜在的应用价值。课题以实验室自创的水相柠檬酸助共沉淀法构建了具有多级纳米片阵列结构的Cu基三元、四元 CuMAl-LDH/rGO（M = Mg、Ni、Co、NiFe等）杂化物催化材料。系统表征了杂化物的结构、形貌及组成。以水相4-硝基苯酚还原反应为模型，研究了系列催化剂的催化加氢活性及循环稳定性。发现含双或三过渡金属的杂化物催化剂催化性能明显优于含单一过渡金属Cu的杂化物CuMgAl-LDH/rGO。基于深入的结构研究和实验探索，从分子水平分析了多级纳米片阵列结构催化剂的催化性能并确定铜及非铜 3d 过渡金属的结构形态、价态、相互作用及其与rGO的协同增强效应，揭示了催化剂的结构-性能关系。通过惰性气氛适度煅烧，将杂化物中LDH层板上的晶格限域铜离子Cu2+经rGO的原位还原得到了rGO负载、非铜复合金属氧化物相限域的小尺寸类核壳型金属@金属氧化物（Cu@Cu2O）高分散铜基催化剂，其催化活性及稳定均得到显著提升。以三维泡沫镍（NF）为基底基于原位生长法制备了系列多级纳米片阵列型CuNiAl/rGO/NF催化剂，其催化活性及循环稳定性能得到大幅度提升。同时以多级纳米片阵列结构杂化物LDH/rGO为载体，以钯纳米簇为前体，通过静电吸附制备了杂化物负载钯纳米簇催化剂，其显示出远高于已报道钯纳米催化剂的催化还原4-NP反应性能。进一步将探索得到的制备方法、结构-性能规律拓展到泡沫镍基底高分散NiFe基LDH纳米催化剂体系，得到了系列多级纳米片阵列型NiFe基LDH/rGO/NF复合电极材料，在电解水反应中表现出优异的性能。课题所得到的规律性结论对设计、合成其它类型多元过渡金属基催化剂及应用具有重要的参考价值。