Generation of an electromotive force by hydrogen‐to‐water oxidation with Pt‐coated oxidized titanium foils

Abstract

We show that chemically induced current densities up to 20 mA cm−2 and an electromotive force (EMF) up to 465 mV are generated during the hydrogen‐to‐water‐oxidation over Pt/TiO2/Ti devices. We prepare the samples by plasma electrolytic oxidation (PEO) of titanium foils and deposition of Pt contact paste. This process yields porous structures and, depending on the anodization voltage, Schottky diode‐type current–voltage curves of various ideality parameters. Our experiments demonstrate that Pt coated anodized titanium can also be utilized as hydrogen sensor; the system offers a number of advantages such as a wide temperature range of operation from −40 to 80 °C, quick response and decay times of signals, and good electrical stability. Idealized sketch of the Pt coated anodized Ti foil and application as hydrogen sensor and electric generator.

Gas sensors based on plasma-electrochemically oxidized titanium foils

“…2a. For batch fabrication of sensors, we applied an automatized plasma-electrolytic oxidation by which the titanium oxide is formed under potential control and current limitation (Schierbaum and El Achhab, 2011). The process led to excellent adhesion and stability of the oxide layer.…”

“…The interaction of H 2 with Pt/TiO 2 /Ti has been previously studied in detail (see the reference of Schierbaum and El Achhab, 2011). Also, oxidizing gases like NO 2 interact with Pt-graphite/TiO 2 /Ti.…”

“…In this device, both the sensitive electrode and the oxide are accessible to gases. For this purpose, we have developed a sensor preparation technique based on plasma electrolytic oxidation of titanium (Schierbaum and El Achhab, 2011) and a printing method for the top, catalytically active electrode, which consists of graphite and nanosized platinum. Thus, the sensor element has a platinum-graphite/TiO 2 /Ti solid-state structure.…”

Combined Galvanostatic and Potentiostatic Plasma Electrolytic Oxidation of Titanium in Different Concentrations of H2SO4

“…In gas sensors, PEO films on titanium exhibit a number of interesting properties. For example, after coating them with graphite or graphite/catalysts mixtures, various gases can be detected at room temperature with high sensitivity [3][4][5][6]. Galvanostatic, potentiostatic and potentiodynamic operating modes are commonly applied [7] and have been compared with respect to surface morphology, phase composition and electrical properties [8].…”

Role of Charge Transfer in Catalytic Hydrogen Oxidation over Platinum

“…Exothermic chemistry at low workfunction metal surface may eject electrons from metal in the form of exoelectrons 2, 3 . Evidence has been mounting [3][4][5][6][7][8][9][10][11][12][13] that exothermic redox chemical reactions at high workfunction surfaces of electron-rich noble and late transition metals may also invoke hot electron excitations that propagate for about a few nanometers into the metal at kinetic energies 0.5−1.2 eV, but below the workfunction barrier for electron ejection from the metal (4.3−5.9 eV 14 ). These excitations must propagate inside the metal rather than in a vacuum, and therefore are tricky to probe directly in experiments and it has been debated in the literature 10,18,19 whether chemicurrent is a phenomenon that has to do with charge transfer surface chemistry at high pressure conditions.…”