Formic Acid Oxidation on Bi-modified Pt Nanoparticles of Various Sizes

Abstract

This work presents oxidation of formic acid on Bi-modified Pt nanoparticles of various sizes. The sizes of the studied Pt nanoparticles range from 1.5 to 5.6 nm (detailed in Rhee, C. K.; Kim, B.-J.; Ham, C.; Kim, Y.-J.; Song, K.; Kwon, K. Langmuir 2009, 25, 7140-7147), and the surfaces of the Pt nanoparticles are modified with irreversibly adsorbed Bi. The investigated coverages of Bi on the Pt nanoparticles are 0.12 and 0.25 as determined by coulometry of the oxidation of adsorbed hydrogen and Bi, and X-ray photoelectron spectroscopy. The cyclic voltammetric behavior of formic acid oxidation reveals that the adsorbed Bi enhances the catalytic activity of Pt nanoparticles by impeding a poison-forming dehydration path with a concomitant promotion of a dehydrogenation path. The chronoamperometric results indicate that elemental Bi and partially oxidized Bi are responsible for the catalytic enhancement, when the Bi coverages on Pt nanoparticles are 0.12 and 0.25, respectively. The size effect of Bi-modified Pt nanoparticles in formic acid oxidation is discussed in terms of specific activity (current per unit surface area) and mass activity (current per unit mass).

Pt Deposits on Bi/Pt NP Catalyst for Formic Acid Oxidation: Catalytic Enhancement and Longer Lifetime

“…Meanwhile, the other dehydrogenation peaking at ∼0.4 V (DH2) occurs concomitantly with dehydration on wide Pt surfaces (e.g., Pt disk). The other two components, named oxidized surface processes (OS1 and OS2), concern FAO behavior on the oxidized surface of Bi/Pt NP and Pt/Bi/Pt NPs above 0.4 V. The OS1 process (roughly in a potential region 0.4−0.7 V) has been suggested on various Bi/Pt surfaces; 65,67,68 however, the OS2 process active above 0.7 V on Pt/Bi/Pt NP is newly proposed in this work. The two FAO processes on oxidized surfaces are critical in understanding the voltammograms to 1.1 V. A detailed discussion is given in Section S4, Supporting Information.…”

“…63,64 On Pt nanoparticles (NP) modified by Bi using irreversible adsorption, the FAO activity was demonstrated to be enhanced by factor of 5. 65 Furthermore, a mass production of Bi-modified Pt NPs for FAO was achieved to fabricate a DFAFC stack of 35 membrane electrode assemblies yielding a power of 300 W, which is certainly an advancement toward the commercialization of DFAFCs. 66 Associated with the commercialization of DFAFCs, another barrier to overcome is the lifetimes of the employed catalysts.…”

“…A base metal whose surface is to modify is simply immersed into a solution containing precursor ions of interesting metals (generally oxygenated anions in solution phase) to induce strong (or irreversible) adsorption, and the adsorbed ionic layers are reduced chemically or electrochemically to stable metal layers on the surface of the base metal. For example, a simple immersion of Pt(111) into a solution of Bi ions has been reported to form irreversibly adsorbed two-dimensional Bi oxide layers on Pt(111) showing a redox behavior after electrochemical oxidation. , On Pt nanoparticles (NP) modified by Bi using irreversible adsorption, the FAO activity was demonstrated to be enhanced by factor of 5 . Furthermore, a mass production of Bi-modified Pt NPs for FAO was achieved to fabricate a DFAFC stack of 35 membrane electrode assemblies yielding a power of 300 W, which is certainly an advancement toward the commercialization of DFAFCs …”

Electrocatalytic properties of Pt-Bi electrodes towards the electrooxidation of formic acid

“…This is commonly realized by alloying or by alteration of the Pt surface with adsorbed foreign metals in amounts less than a full monolayer. 17 According to literature data, the activity of a Pt catalyst modified with Bi depends on the shape of the Pt nanocrystals, 18 the size of the particles 19 and Pt catalyst loading. Irreversibly adsorbed Bi.…”

Formic Acid Oxidation Depending on Rotating Speed of Smooth Pt Disk Electrode

“…Because the potentials for poison oxidation is known to be higher than the potential for the dehydrogenation path, removal or inhibition of poison is one of the research directions toward practical Pt electrocatalysts of formic acid oxidation. For example, one way to boost formic acid oxidation on Pt is the modification of Pt surfaces with Bi, which inhibits poison formation and simultaneously enhances dehydrogenation via ensemble mechanism [3][4][5][6][7][8].…”