Two Birds with One Stone: Concurrent Ligand Removal and Carbon Encapsulation Decipher Thickness-Dependent Catalytic Activity
Kun Guo, Litao Chang, Ning Li, Lipiao Bao, Samir de Moraes Shubeita, Aliaksandr Baidak, Zhixin Yu*, and Xing Lu*
https://pubs.acs.org/doi/10.1021/acs.nanolett.2c03181
Nano Lett. 2022. Doi:10.1021/acs.nanolett.2c03181
Abstract
A carbon shell encapsulating a transition metal-based core has emerged as an intriguing type of catalyst structure, but the effect of the shell thickness on the catalytic properties of the buried components is not well known. Here, we present a proof-of-concept study to reveal the thickness effect by carbonizing the isotropic and homogeneous oleylamine (OAm) ligands that cover colloidal MoS2. A thermal treatment turns OAm into a uniform carbon shell, while the size of MoS2monolayers remains identical. When evaluated toward an acidic hydrogen evolution reaction, the calcined MoS2catalysts deliver a volcano-type activity trend that depends on the calcination temperature. Rutherford backscattering spectrometry and depth-profiling X-ray photoelectron spectroscopy consistently provide an accurate quantification of the carbon shell thickness. The same variation pattern of catalytic activity and carbon shell thickness, aided by kinetic studies, is then persuasively justified by the respective limitations of electron and proton conductivities on the two branches of the volcano curve.
