INSTITUTE OF PHYSICS PUBLISHING MEASUREMENT SCIENCE AND TECHNOLOGY Meas. Sci. Technol. 16 (2005) 54–59 doi:10.1088/0957-0233/16/1/008 Automated electrochemical synthesis and characterization of TiO 2 supported Au nanoparticle electrocatalysts Sung-Hyeon Baeck 1 , Thomas F Jaramillo 2 , Alan Kleiman-Shwarsctein 2 and Eric W McFarland 2 1 Department of Chemical Engineering, Inha University, Inchon, 402751 Korea 2 Department of Chemical Engineering, University of California, Santa Barbara, CA 93106-5080, USA E-mail: mcfar@engineering.ucsb.edu Received 16 April 2004 Published 16 December 2004 Online at stacks.iop.org/MST/16/54 Abstract Automated systems for electrochemical synthesis and high throughput screening of catalytic materials were developed and used to prepare a library of nanoparticulate gold supported on TiO 2 . A two-dimensional array (library) of Au was synthesized by pulsed cathodic electrodeposition onto a thermally oxidized titanium dioxide substrate. Variations in particle size across the library were created by changing the deposition time (number of pulses). Longer deposition times led to increased Au particle sizes and greater density of Au on the surface. High throughput electrochemical screening was used to characterize the electrocatalytic activity of the supported Au clusters for: (1) photoelectrochemical water oxidation and (2) CO electro-oxidation. Au films synthesized with 5 ms pulses between 3 and 10 s of total deposition time demonstrated the greatest activity for photodecomposition of water (20–40% greater than pure TiO 2 ). For CO electro-oxidation, it was found that the smallest Au particle (<10 nm, 1 s total deposition time) was most active, consistent with previous research in this area. Keywords: combinatorial chemistry, pulsed electrodeposition, nanoparticles, Au/TiO 2 1. Introduction Combinatorial chemistry involves the deliberate creation and screening of very large numbers of new materials from different combinations of specific building block atoms and molecules [1–5]. As a discovery methodology, combinatorial chemistry is not new to materials science and catalysis [1–4]. Informally, scientists have long tried to discover new materials with special properties using methods which closely resemble today’s ‘combinatorial chemistry’. In 1970, a formal strategy for synthesizing and testing large collections of multicomponent inorganic chemical systems was introduced by Joseph Hanak at RCA Laboratories who developed physical vapour deposition (PVD) methods for the synthesis of diverse multicomponent compounds for use as superconductors, ceramics, photovoltaics and luminescent materials [5, 6]. Applied to functional inorganic materials, these methods were later used to rapidly investigate large numbers of mixed metal oxides as potential phosphors, catalysts and dielectric materials [2, 3, 6]. Automated electrochemical methods for creating and screening collections of compositionally varied materials (libraries) for photoelectrochemical performance have recently been described [7, 8]. Electrochemical methods lend themselves well to the combinatorial synthesis of inorganic materials because of the many synthesis variables under direct control, such as voltage, current density and electrolyte, which can be varied readily using automated programmable systems, resulting in diversity of structure and composition. 0957-0233/05/010054+06$30.00 © 2005 IOP Publishing Ltd Printed in the UK 54