Ultrafine NiO Nanosheets Stabilized by TiO2 from ... - ACS Publications

May 9, 2016 - Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese. Academy ...
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Ultrafine NiO Nanosheets Stabilized by TiO from Monolayer NiTiLDH Precursors: An Active Water Oxidation Electrocatalyst Yufei Zhao, Xiaodan Jia, Guangbo Chen, Lu Shang, Geoffrey I.N. Waterhouse, Li-Zhu Wu, Chen-Ho Tung, Dermot O'Hare, and Tierui Zhang J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.6b01606 • Publication Date (Web): 09 May 2016 Downloaded from http://pubs.acs.org on May 11, 2016

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Ultrafine NiO Nanosheets Stabilized by TiO2 from Monolayer NiTi-LDH Precursors: An Active Water Oxidation Electrocatalyst Yufei Zhao,a Xiaodan Jia,ab Guangbo Chen,ab Lu Shang,a Geoffrey I.N. Waterhouse,c Li-Zhu Wu,a Chen-Ho Tung,a Dermot O’Hared and Tierui Zhang*a a. Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China b. Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of the Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi’an 710069, P. R. China c. School of Chemical Sciences, The University of Auckland, Auckland 1142, New Zealand d. Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA, United Kingdom

ABSTRACT: Faceted NiO nanoparticles preferentially exposing high surface energy planes demand attention due to their excellent electrocatalytic properties. However, the activity of faceted NiO nanoparticles generally remains sub-optimal due to their large lateral size and thickness, which severely limits the availability of coordinatively unsaturated active reactive edge and corner sites. Here, ultrafine NiO nanosheets with a platelet size of ~4.0 nm andthickness (~1.1 nm) stabilized by TiO2 were successfully prepared by calcination of a monolayer layered double hydroxide precursor. The ultrafine NiO nanosheets displayed outstanding performance in electrochemical water oxidation due to a high proportion of reactive NiO {110} facets, intrinsic Ni3+ and Ti3+ sites and abundant interfaces, which act synergistically to promote H2O adsorption and facilitate charge transfer. 1

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KEYWORDS: layered double hydroxide, electrocatalysis, ultrathin nanosheets, NiO, oxygen evolution reaction

INTRODUCTION NiO nanoparticles have attracted attention due to their widespread application in electrochemistry,1-8 sensors and catalysis.9 Recently, faceted NiO nanoparticles exposing high surface energy planes have been the target of intense research focus due to their significantly enhanced catalytic performance.10-11 However, the catalytic performance of these faceted NiO nanoparticles remains sub-optimal due to their large lateral size and thickness leading to modest specific surface areas and limited exposure of the desired reactive facets. This has motivated the development of ultrathin two-dimensional (2D) nanomaterials, such as nanosheets, that preferentially expose a higher percentage of active sites.12-13 However, most ultrathin 2D materials reported to date have lateral dimensions of several hundred nanometers, too large to dramatically improve catalytic performance due to the limited availability of edge and corner sites which possess high reactivity due to coordinative unsaturation. Synthesis methods that can yield both ultrafine and ultrathin NiO nanosheets are demanded.14-15 The surface energy of NiO facets follows the order: {110} ≈ {101} > {113} > {100}.16 Since surface chemical reactivity generally increases with surface energy,17 it is highly desirable to synthesize ultrafine NiO nanosheets (diameter