摘要
The pyrolysis of zeolitic imidazolate frameworks(ZIFs) is becoming a popular approach for the synthesis of catalysts comprising porphyrin-like metal single atom catalysts(SACs) on N-doped carbons(M-N-C).Understanding the structural evolution of M-N-C as a function of ZIF pyrolysis temperature is important for realizing high performance catalysts.Herein,we report a detailed investigation of the evolution of Zn single atom catalyst sites during the pyrolysis of ZIF-8 at temperatures ranging from 500 to 900℃.Results from Zn L-edge and Zn K-edge X-ray absorption spectroscopy studies reveal that tetrahedral ZnN4 centers in ZIF-8 transform to porphyrin-like ZnN4 centers supported on N-doped carbon at temperatures as low as 600℃.As the pyrolysis temperature increased in the range 600-900℃,the Zn atoms moved closer to the N4 coordination plane.This subtle geometry change in the ZnN4 sites alters the electron density on the Zn atoms(formally Zn2+),strongly impacting the catalytic performance for the peroxidase-like decomposition of H2 O2.The catalyst obtained at 800℃(Zn-N-C-800) offered the best performance for H2 O2 decomposition.This work provides valuable new insights about the evolution of porphyrin-like single metal sites on N-doped carbons from ZIF precursors and the factors influencing SAC activity.
高温热解金属有机骨架(ZIFs)是一种合成含类卟啉单原子碳材料的有效方式.理解煅烧产物中单原子位点在热解过程中的构型变化,对实现高性能单原子催化材料具有重要意义.因此,本工作系统地研究了在ZIF-8煅烧过程中(500~900℃)锌单原子中心的构型演变.同步辐射吸收谱结果表明:ZIF-8前驱体中四面体构型的锌单子中心在600℃时开始转变为类卟啉锌中心(锌中心凸出卟啉平面);并随着温度升高至900℃,锌中心逐渐接近N4卟啉平面.由于Zn N4中心位点的几何构型变化改变了锌中心原子的电子密度分布,因此其在降解H2O2中表现不同的催化活性(800℃煅烧得到的锌单原子产物性能最优).本工作为理解ZIF煅烧中单原子的构型演变以及其催化性能提供了新思路.
作者
Qing Wang
Toshiaki Ina
Wan-Ting Chen
Lu Shang
Fanfei Sun
Shanghai Wei
Dongxiao Sun-Waterhouse
Shane G.Telfer
Tierui Zhang
Geoffrey I.N.Waterhouse
王青;伊奈稔哲;陈婉婷;尚露;孙凡飞;魏上海;Dongxiao Sun-Waterhouse;Shane G.Telfer;张铁锐;Geoffrey I.N.Waterhouse(School of Chemical Sciences,The University of Auckland.Auckland 1142,New Zealand;Research&Utilization Division,Japan Synchrotron Radiation Research Institute,Kouto 679-5148,Japan;Key Laboratory of Photochemical Conversion and Optoelectronic Materials,Technical Institute of Physics and Chemistry,Chinese Academy of Sciences.Beijing 100190,China;Shanghai Synchrotron Radiation Facility,Shanghai Institute of Applied Physics.Chinese Academy of Sciences,Shanghai 201204,China;Department of Chemical and Materials Engineering,Faculty of Engineering,The University of Auckland,Auckland 1142,New Zealand;MacDiarmid Institute for Advanced Materials and Nanotechnology,Massey University,Palmerston North 4442,New Zealand)
基金
supported by the Ministry of Business, Innovation and Employment Catalyst Fund (MAUX 1609)
the University of Auckland Faculty Research Development Fund
the MacDiarmid Institute for Advanced Materials and Nanotechnology
a generous philanthropic donation from Greg and Kathryn Trounson。
作者简介
王青,received her M.S.degree in Materials Science from the University of Chinese Academy of Sciences.Currently,she is a Ph.D.cancliclate at the University of Auckland,New Zealand,under the supervision of Professor Geoffrey Waterhouse.Her resedrch focuses on the development of non-precious metal catalysts and electrocatalysts for energy conversion and other applications;Corresponding author:Geoffrey I.N.Waterhouse,completed a Ph.D.degree in Chemistry at the University of Auckland in 2003.Currently he is the Energy Theme leader in the MacDiarmid Institute for Advanced for Advanced Materials and Nano technology(a New Zealand Centre of Research Excellence),and a Chair Professor of both the South China University of Technology and Shandong Agricultural University.His research interest includes solar energy capture technologies,photocatalysis,photonic band gap materials,and biosensors.E-mail address:g.waterhouse@auckland.ac.nz。
