Abundance of Low-Energy Oxygen Vacancy Pairs Dictates the Catalytic Performance of Cerium-Stabilized Zirconia.

Cerium-stabilized zirconia (Ce1-xZrxOy, CZO) is renowned for its superior oxygen storage capacity (OSC), a key property long believed to be beneficial to catalytic oxidation reactions. However, 50% Ce-containing CZO recorded with the highest OSC has disappointingly poor performance in catalytic oxidation reactions compared to those with higher Ce contents but lower OSC ability. Here, we employ global neural network (G-NN)-based potential energy surface exploration methods to establish the first ternary phase diagram for bulk structures of CZO, which identifies three critical compositions of CZO, namely, 50, 60, and 80% Ce-containing CZO that are thermodynamically stable under typical synthetic conditions. 50% Ce-containing CZO, although having the highest OSC, exhibits the lowest O vacancy (Ov) diffusion rate. By contrast, 60% Ce-containing CZO, despite lower OSC (33.3% OSC compared to that of 50% Ce-containing CZO), reaches the highest Ov diffusion ability and thus offers the highest CO oxidation catalytic performance. The physical origin of the high performance of 60% Ce-containing CZO is the abundance of energetically favorable Ov pairs along the ⟨110⟩ direction, which reduces the energy barrier of Ov diffusion in the bulk and promotes O2 activation on the surface. Our results clarify the long-standing puzzles on CZO and point out that 60% Ce-containing CZO is the most desirable composition for typical CZO applications.

Separation of chloroform from a dilute solution using a cyclic peptide nanotube: A molecular dynamics study.

This work firstly explored the potential application of a cyclic peptide nanotube (CPNT) in the separation of chloroform from a dilute solution. Four hydrophobic CPNTs of 8 × (WL)4,5 and 8 × (AL)4,5 all exhibit excellent adsorption characteristics to chloroform. The CPNT diameter, side chain structures and the concentration of chloroform in a solution all affect the adsorption characteristics of chloroform. CHCl3 molecules are overwhelmingly adsorbed on the surfaces of these CPNTs as a cluster, and sporadically reside inside the channels, consistent with the chloroform's potentials of mean force (PMFs) inside and outside the channels. The distribution characteristics, molecular orientations and interactions with the surroundings of chloroform inside and outside four CPNTs embedded in individual dilute CHCl3/water solutions were analyzed in detail, providing referable information of the adsorption characteristics of a hydrophobic CPNT to chloroform.