Co-containing layered double hydroxides (LDHs) are potential non-noble-metal catalysts for the aerobic oxidation of alcohols. However, the intrinsic activity of bulk LDHs is relatively low. In this work, we fabricated ultrathin and vacancy-rich nanosheets by exfoliating bulk CoAl-LDHs, which were then assembled with graphite oxide (GO) to afford a hybrid CoAl-ELDH/GO catalyst. TEM, AFM, and positron annihilation spectrometry indicate that the thickness of the exfoliated LDH platelets is about 3 nm, with a large number of vacancies in the host layers. Fourier transformed XAFS functions show that the Co–O and Co····Co coordination numbers (5.5 and 2.8, respectively) in the hybrid CoAl-ELDH/GO material are significantly lower than the corresponding values in bulk CoAl-LDHs (6.0 and 3.8, respectively). Furthermore, in addition to the oxygen vacancies (V_O) and cobalt vacancies (V_Co), CoAl-ELDH/GO also contains negatively charged V_Co–Co–OH^δ− sites and exposed lattice oxygen sites. CoAl-ELDH/GO shows excellent performance as a catalyst for the aerobic oxidation of benzyl alcohol, with a TOF of 1.14 h^–1; this is nearly five times that of the unexfoliated bulk CoAl-LDHs (0.23 h^–1) precursor. O₂-TPD and DRIFT spectroscopy declare that the oxygen storage capacity and mobility are facilitated by the oxygen vacancies and surface lattice oxygen sites. Meanwhile, DFT calculations of adsorption energy show that benzyl alcohol is strongly adsorbed on the oxygen vacancies and negatively charged V_Co–Co–OH^δ− sites. A kinetic isotope effect study further illustrates that the vacancy-rich CoAl-ELDH/GO catalyst accelerates the cleavage of the O–H bond in benzyl alcohol. Finally, we show that the hybrid CoAl-ELDH/GO material exhibits excellent catalytic activity and selectivity in the oxidation of a range of other benzylic and unsaturated alcohols.

中文翻译：

---

超薄和空位丰富的CoAl层状双氢氧化物/石墨氧化物催化剂：乙醇氧化中钴空位和氧空位的促进作用

含钴的层状双氢氧化物（LDHs）是潜在的非贵金属催化剂，用于酒精的好氧氧化。但是，大量LDH的固有活性相对较低。在这项工作中，我们通过剥落大量的CoAl-LDHs来制造超薄且富含空位的纳米片，然后将其与氧化石墨（GO）组装在一起以提供混合的CoAl-ELDH / GO催化剂。TEM，AFM和正电子an没光谱法表明，剥落的LDH血小板的厚度约为3 nm，在宿主层中有大量空位。傅立叶变换的XAFS函数表明，混合CoAl-ELDH / GO材料中的Co-O和Co···Co配位数（分别为5.5和2.8）显着低于散装CoAl-LDHs中的相应值（6.0和0.5）。 3.8）。此外，_ö）和钴空缺（V_有限公司），煤- ELDH / GO还包含带负电荷的V_共同-Co-OH ^δ-部位并暴露晶格氧位点。CoAl-ELDH / GO表现出优异的催化活性，可用于苯甲醇的好氧氧化，TOF为1.14 h ^–1；这是未剥落的CoAl-LDHs（0.23 h ^–1）前体的近五倍。O ₂ -TPD和DRIFT光谱表明，氧空位和表面晶格氧位促进了氧的存储能力和迁移率。同时，DFT吸附能的计算表明，苯甲醇在氧空位上被强烈吸附，并且带负电的V _Co –Co–OH^δ-位点。动力学同位素效应研究进一步表明，富含空位的CoAl-ELDH / GO催化剂可促进苄醇中O-H键的裂解。最后，我们表明杂化的CoAl-ELDH / GO材料在一系列其他苄基和不饱和醇的氧化中表现出出色的催化活性和选择性。