An Atomistic View of Electrodics at the Platinum Surface

<div><div><div><p>Platinum (Pt) is a benchmarked catalyst for several electrochemical processes, however an atomistic insight into its electrodics at the electrode-electrolyte interface is still lacking. In this study, we aim to capture the chemical changes of Pt surfaces brought on by an applied potential in an electrolyte of pH~5, which can address the catalytic efficacy and stability of different crystallographic orientations under varying applied bias. Through a combined experimental and reactive molecular dynamics simulation approach, we uncover the effect of charge build up on the surface of the Pt electrode, which can be directed towards capacitive and faradaic processes. By introducing a simulated applied potential, which is compared to experimental potential by equating charge density ( in the range -0.2 mC/cm2 to 0.2 mC/cm2 ), we unravel the electrochemical processes on Pt (in slightly acidic pH). At reductive potentials of ~0.3-0.0 V vs RHE, we visualize phenomenon such as under potential hydrogen adsorption (HUPD) and hydrogen evolution/oxidation reaction. While oxidative potentials in the range ~1.2-1.6 V vs RHE see platinum oxide (Pt-O) formation, and platinum leaching off the surface. The theoretical potential and plane dependence of these phenomenon (HUPD, Pt-O, etc.) are verified with experiments, and hence it brings a new platform for computationally viable electrode-electrolyte studies.</p></div></div></div>

An Atomistic View of Electrodics at the Platinum Surface

<div><div><div><p>Platinum (Pt) is a benchmarked catalyst for several electrochemical processes, however an atomistic insight into its electrodics at the electrode-electrolyte interface is still lacking. In this study, we aim to capture the chemical changes of Pt surfaces brought on by an applied potential in an electrolyte of pH~5, which can address the catalytic efficacy and stability of different crystallographic orientations under varying applied bias. Through a combined experimental and reactive molecular dynamics simulation approach, we uncover the effect of charge build up on the surface of the Pt electrode, which can be directed towards capacitive and faradaic processes. By introducing a simulated applied potential, which is compared to experimental potential by equating charge density ( in the range -0.2 mC/cm2 to 0.2 mC/cm2 ), we unravel the electrochemical processes on Pt (in slightly acidic pH). At reductive potentials of ~0.3-0.0 V vs RHE, we visualize phenomenon such as under potential hydrogen adsorption (HUPD) and hydrogen evolution/oxidation reaction. While oxidative potentials in the range ~1.2-1.6 V vs RHE see platinum oxide (Pt-O) formation, and platinum leaching off the surface. The theoretical potential and plane dependence of these phenomenon (HUPD, Pt-O, etc.) are verified with experiments, and hence it brings a new platform for computationally viable electrode-electrolyte studies.</p></div></div></div>

Platinum Based Nanoparticles Produced by a Pulsed Spark Discharge as a Promising Material for Gas Sensors

We have applied spark ablation technology for producing nanoparticles from platinum ingots (purity of 99.97 wt. %) as a feed material by using air as a carrier gas. A maximum production rate of about 400 mg/h was achieved with an energy per pulse of 0.5 J and a pulse repetition rate of 250 Hz. The synthesized nanomaterial, composed of an amorphous platinum oxide PtO (83 wt. %) and a crystalline metallic platinum (17 wt. %), was used for formulating functional colloidal ink. Annealing of the deposited ink at 750 °C resulted in the formation of a polycrystalline material comprising 99.7 wt. % of platinum. To demonstrate the possibility of application of the formulated ink in printed electronics, we have patterned conductive lines and microheaters on alumina substrates and 20 μm thick low-temperature co-fired ceramic (LTCC) membranes with the use of aerosol jet printing technology. The power consumption of microheaters fabricated on LTCC membranes was found to be about 140 mW at a temperature of the hot part of 500 °C, thus allowing one to consider these structures as promising micro-hotplates for metal oxide semiconductor (MOS) gas sensors. The catalytic activity of the synthesized nanoparticles was demonstrated by measuring the resistance transients of the non-sintered microheaters upon exposure to 2500 ppm of hydrogen.

Hydrogen Oxidation Artifact During Platinum Oxide Reduction in Cyclic Voltammetry Analysis of Low-Loaded PEMFC Electrodes

An artifact appearing during the cathodic transient of cyclic voltammograms (CVs) of low-loaded platinum on carbon (Pt/C) electrodes in proton exchange membrane fuel cells (PEMFCs) was examined. The artifact appears as an oxidation peak overlapping the reduction peak associated to the reduction of platinum oxide (PtOx). By varying the nitrogen (N2) purge in the working electrode (WE), gas pressures in working and counter electrode, upper potential limits and scan rates of the CVs, the artifact magnitude and potential window could be manipulated. From the results, the artifact is assigned to crossover hydrogen (H2X) accumulating in the WE, once the electrode is passivated towards hydrogen oxidation reaction (HOR) due to PtOx coverage. During the cathodic CV transient, PtOx is reduced and HOR spontaneously occurs with the accumulated H2X, resulting in the overlap of the PtOx reduction with the oxidation peak. This feature is expected to occur predominantly in CV analysis of low-loaded electrodes made of catalyst material, whose oxide is inactive towards HOR. Further, it is only measurable while the N2 purge of the WE is switched off during the CV measurement. For higher loaded electrodes, the artifact is not observed as the electrocatalysts are not fully inactivated towards HOR due to incomplete oxide coverage, and/or the currents associated with the oxide reduction are much larger than the spontaneous HOR of accumulated H2X. However, owing to the forecasted reduction in noble metal loadings of catalyst in PEMFCs, this artifact is expected to be observed more often in the future.