Conformal Solution Deposition of Pt-Pd Titania Nanocomposite Coatings for Light-Assisted Formic Acid Electro-Oxidation

Falk Muench; Gumaa A El-Nagar; Tim Tichter; Alexander Zintler; Ulrike Kunz; Leopoldo Molina-Luna; Vadim Sikolenko; Chiara Pasquini; Iver Lauermann; Christina Roth

doi:10.1021/acsami.9b12783

Conformal Solution Deposition of Pt-Pd Titania Nanocomposite Coatings for Light-Assisted Formic Acid Electro-Oxidation

ACS Appl Mater Interfaces. 2019 Nov 20;11(46):43081-43092. doi: 10.1021/acsami.9b12783. Epub 2019 Nov 11.

Authors

Falk Muench¹, Gumaa A El-Nagar^{2

3}, Tim Tichter, Alexander Zintler¹, Ulrike Kunz¹, Leopoldo Molina-Luna¹, Vadim Sikolenko, Chiara Pasquini, Iver Lauermann³, Christina Roth

Affiliations

¹ Department of Materials and Earth Sciences , Technische Universität Darmstadt , Alarich-Weiss-Straße 2 , 64287 Darmstadt , Germany.
² Chemistry Department, Faculty of Science , Cairo University , Cairo 12613 , Egypt.
³ Helmholtz-Zentrum Berlin für Materialien und Energie , Berlin 12489 , Germany.

PMID: 31647212
DOI: 10.1021/acsami.9b12783

Abstract

Many nanofabrication processes require sophisticated equipment, elevated temperature, vacuum or specific atmospheric conditions, templates, and exotic chemicals, which severely hamper their implementation in real-world applications. In this study, we outline a fully wet-chemical procedure for equipping a 3D carbon felt (CF) substrate with a multifunctional, titania nanospike-supported Pt-Pd nanoparticle (Pt-Pd-TiO₂@CF) layer in a facile and scalable manner. The nanostructure, composition, chemical speciation, and formation of the material was meticulously investigated, evidencing the conformal coating of the substrate with a roughened layer of nanocrystalline rutile spikes by chemical bath deposition from Ti³⁺ solutions. The spikes are densely covered by bimetallic nanoparticles of 4.4 ± 1.1 nm in size, which were produced by autocatalytic Pt deposition onto Pd seeds introduced by Sn²⁺ ionic layer adsorption and reaction. The as-synthesized nanocomposite was applied to the (photo)electro-oxidation of formic acid (FA), exhibiting a superior performance compared to Pt-plated, Pd-seeded CF (Pt-Pd@CF) and commercial Pt-C, indicating the promoting electrocatalytic role of the TiO₂ support. Upon UV-Vis illumination, the performance of the Pt-Pd-TiO₂@CF electrode is remarkably increased (22-fold), generating a current density of 110 mA cm^-2, distinctly outperforming titania-free Pt-Pd@CF (5 mA cm^-2) and commercial Pt-C (6 mA cm^-2) reference catalysts. In addition, the Pt-Pd-TiO₂@CF showed a much better stability, characterized by a very high poisoning tolerance for in situ-generated CO intermediates, whose formation is hindered in the presence of TiO₂. This overall performance boost is attributed to a dual enhancement mechanism (∼30% electrocatalytic and ∼70% photoelectrocatalytic). The photogenerated electrons from the TiO₂ conduction band enrich the electron density of the Pt nanoparticles, promoting the generation of active oxygen species on their surfaces from adsorbed oxygen and water molecules, which facilitate the direct FA electro-oxidation into CO₂.

Keywords: electroless plating; formic acid electro-oxidation; fuel cells; photoelectrocatalysis; successive ionic layer adsorption and reaction; titania-supported nanoparticles.