On the Substantially Improved Photoelectrochemical Properties of Nanoporous WO 3 Through Surface Decoration with RuO 2
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On the Substantially Improved Photoelectrochemical Properties of Nanoporous WO3 Through Surface Decoration with RuO2 Csaba Janáky & Wilaiwan Chanmanee & Krishnan Rajeshwar Published online: 18 November 2013 # Springer Science+Business Media New York 2013
Abstract Solar fuel generation, either through photochemical or photoelectrochemical (PEC) routes, is one of the most prominent pathways to harvest sunlight in order to contribute to a diversified and sustainable energy supply. Oxygen evolution reaction (OER) from aqueous solutions is the half reaction of different energy related reaction schemes, most importantly stoichiometric water splitting (H2 generation) or CO2 reduction. In this paper, we present PEC water oxidation (OER) on nanoporous WO3 films, decorated with RuO2 nanoparticles. The morphology and the composition of these nanostructured assemblies were characterized by high-resolution scanning electron microscopy, X-ray photoelectron spectroscopy, and cyclic voltammetry while their photo-electrochemical behavior was evaluated by photovoltammetry and incident photon-to-current conversion efficiency (IPCE) measurements. The O2 evolution capability was directly assessed by determining the amount of evolved O2 gas during PEC oxidation of water. The RuO2 electrocatalyst substantially increased photoanodic current flow through facile transfer of photogenerated holes from WO3 to the solution, thereby improving interfacial charge transfer kinetics. Both absolute and relative enhancement of photocurrents was analyzed as a function of the applied external bias potential giving important insight into the mechanistic details.
This paper is dedicated to Prof. Achille De Battisti in recognition of his contributions to the field of electrocatalysis. One of the authors (KR) has fond memories of Prof. De Battisti’s collegiality and friendship and our interactions occurred in many meeting venues and parts of the globe over the years. We wish him the best. C. Janáky : W. Chanmanee : K. Rajeshwar (*) Department of Chemistry and Biochemistry, The University of Texas at Arlington, Planetarium Place, Arlington, TX 76019, USA e-mail: [email protected] C. Janáky (*) Department of Physical Chemistry and Materials Science, University of Szeged, Aradi sq. 1, Szeged 6720, Hungary e-mail: [email protected]
Furthermore, the decisive roles of the amount of RuO2 cocatalyst and thermal pretreatment were established by synthesizing hybrid assemblies with different RuO2 coverage, and applying subsequent thermal treatment, respectively. Through careful optimization of the composition of the hybrid material, the IPCE value doubled at lower bias potentials and was increased close to the theoretical 100 % limit at higher positive potential values. These results demonstrate the synergy gained by combining the excellent photoanodic properties of nanoporous WO3 with the robust O2 evolution capabilities of RuO2. Keywords Water splitting . Co-catalyst . Semiconductor . Solar energy . Synergy
Introduction Sunlight is undoubtedly one of the mos
