Tan Zicong, Chen Yu-Cheng, Zhang Jieru, Chou Jyh-Pin, Hu Alice, Peng Yung-Kang
Department of Chemistry, City University of Hong Kong, Hong Kong, S.A.R. China.
Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, S.A.R. China.
Chemistry. 2020 Aug 17;26(46):10598-10606. doi: 10.1002/chem.202001597. Epub 2020 Jul 23.
It is known that the interplay between molecules and active sites on the topmost surface of a solid catalyst determines its activity in heterogeneous catalysis. The electron density of the active site is believed to affect both adsorption and activation of reactant molecules at the surface. Unfortunately, commercial X-ray photoelectron spectroscopy, which is often adopted for such characterization, is not sensitive enough to analyze the topmost surface of a catalyst. Most researchers fail to acknowledge this point during their catalytic correlation, leading to different interpretations in the literature in recent decades. Recent studies on pristine Cu O [Nat. Catal. 2019, 2, 889; Nat. Energy 2019, 4, 957] have clearly suggested that the electron density of surface Cu is facet dependent and plays a key role in CO reduction. Herein, it is shown that pristine CeO can reach 2506/1133 % increase in phosphatase-/peroxidase-like activity if the exposed surface is wisely selected. By using NMR spectroscopy with a surface probe, the electron density of the surface Ce (i.e., the active site) is found to be facet dependent and the key factor dictating their enzyme-mimicking activities. Most importantly, the surface area of the CeO morphologies is demonstrated to become a factor only if surface Ce can activate the adsorbed reactant molecules.
众所周知，固体催化剂最外层表面上的分子与活性位点之间的相互作用决定了其在多相催化中的活性。据信，活性位点的电子密度会影响表面反应物分子的吸附和活化。不幸的是，常用于此类表征的商业X射线光电子能谱对催化剂最外层表面的分析不够灵敏。大多数研究人员在催化关联过程中未能认识到这一点，导致近几十年来文献中有不同的解释。最近对原始CuO的研究[《自然催化》2019年，第2卷，第889页；《自然能源》2019年，第4卷，第957页]清楚地表明，表面Cu的电子密度取决于晶面，并且在CO还原中起关键作用。在此表明，如果明智地选择暴露表面，原始CeO的磷酸酶/过氧化物酶样活性可提高2506/1133%。通过使用带有表面探针的核磁共振光谱，发现表面Ce（即活性位点）的电子密度取决于晶面，并且是决定其类酶活性的关键因素。最重要的是，只有当表面Ce能够活化吸附的反应物分子时，CeO形态的表面积才会成为一个因素。
