Supported catalysts are widely used in heterogeneous catalysis, and the influences of the interfacial interaction between the active phase and support and the interface density on the catalytic performance have attracted great attention. Generally, the traditional supported catalysts are prepared via two main methods, i.e., impregnation and precipitation, which normally render limited interface density and relatively weak interfacial interaction, further affecting the catalytic activity and stability. In view of these problems, Xuefeng Guo’s Group put forward a reverse-design surrounded catalyst, and develop a facile and general strategy, i.e., ion-exchange inverse loading method, to fabricate the surrounded catalysts. During the process, the active metal hydroxide precursor (Ap, metal ions Am+) is added into the solution of support precursor (Bp, metal ions Bn+) and the ion-exchange reaction takes place driven by the difference of solubility product. By replacement of metal ion Am+ with Bn+ on the surface of Ap to form mixed metal hydroxides, core-shell structured A@B surrounded catalyst can be achieved followed by the subsequent calcination and reduction. Based on the control over the degree of ion exchange and the various compositions of Ap and Bp, A@B surrounded catalysts with inverse structure and gradient structure can also be obtained. The unique surrounded catalysts present not only higher interface density and mutually changed interface, but also high stability due to the physical isolation of active phase by the support, revealing superior catalytic performance to the traditional supported catalysts. For instance, the Ni@Al2O3-IE surrounded catalyst displays excellent low-temperature activity and high-temperature stability simultaneously during CO methanation.
The concept of “surrounded catalyst” has been proposed for the first time to define the catalyst with unique structure of active core surrounded by support and the mutually changed interface. The new surrounded catalyst presents great potential application in heterogeneous catalysis as the upgrade of supported catalyst.
This work entitled “Surrounded catalysts prepared by ion-exchange inverse loading” has been published recently on Science Advances(2020, 6, eaay 7031). Panpan Hao, the PhD student of Nanjing University, is the first author of the paper. Researcher Ming Lin of the Institute of Materials Research and Engineering in Singapore assisted the study in the characterization of the transmission electron microscopy. Professor Weiping Ding, the head of the mesoscopic catalytic team at Nanjing University, participated in the discussion of this paper. This work was financially supported by National Natural Science Foundation of China, the National Key Technology R&D Program of China, the Fundamental Research Funds for the Central Universities, and the Hubei Key Laboratory for Processing and Application of Catalytic Materials.
