A Simulation Study of Pt Particle Degradation During Potential Cycling Using a Dissolution/Deposition Model

Glucose-Oxygen Biofuel Cell with Biotic and Abiotic Catalysts: Experimental Research and Mathematical Modeling

The demand for alternative sources of clean, sustainable, and renewable energy has been a focus of research around the world for the past few decades. Microbial/enzymatic biofuel cells are one of the popular technologies for generating electricity from organic substrates. Currently, one of the promising fuel options is based on glucose due to its multiple advantages: high energy intensity, environmental friendliness, low cost, etc. The effectiveness of biofuel cells is largely determined by the activity of biocatalytic systems applied to accelerate electrode reactions. For this work with aerobic granular sludge as a basis, a nitrogen-fixing community of microorganisms has been selected. The microorganisms were immobilized on a carbon material (graphite foam, carbon nanotubes). The bioanode was developed from a selected biological material. A membraneless biofuel cell glucose/oxygen, with abiotic metal catalysts and biocatalysts based on a microorganism community and enzymes, has been developed. Using methods of laboratory electrochemical studies and mathematical modeling, the physicochemical phenomena and processes occurring in the cell has been studied. The mathematical model includes equations for the kinetics of electrochemical reactions and the growth of microbiological population, the material balance of the components, and charge balance. The results of calculations of the distribution of component concentrations over the thickness of the active layer and over time are presented. The data obtained from the model calculations correspond to the experimental ones. Optimization for fuel concentration has been carried out.

First-principles investigation of electrochemical dissolution of Pt nanoparticles and kinetic simulation

Dissolution is the primary route of Pt nanoparticle degradation in electrochemical devices, e.g., fuel cells. Investigation of potential-dependent dissolution kinetics of Pt nanoparticles is crucial to optimize the nanoparticle size and operating conditions for better performance. A mean-field kinetic theory under the steady-state approximation, combined with atomistic thermodynamics and Wulff construction, was developed to study the interplay between oxygen chemisorption, electrode potential, and particle size on the dissolution of Pt nanoparticles. We found that although oxygen chemisorption from electrode potential-induced water splitting can stabilize Pt nanoparticles through decreasing the surface energy and increasing the redox potential, the electrode potential plays a more decisive role in facilitating the dissolution of Pt nanoparticles. In comparison with the minor effect of oxygen chemisorption, an increase in the particle size, though reducing the dispersion, has a more significant effect on the suppression of the dissolution. These theoretical understandings on the effects of electrode potential and particle size on the dissolution are crucial for optimizing the nanoparticle size under oxidative operating conditions.

Dissolution of Platinum in the Operational Range of Fuel Cells

One of the most important practical issues in low-temperature fuel-cell catalyst degradation is platinum dissolution. According to the literature, it initiates at 0.6-0.9 V_RHE, whereas previous time- and potential-resolved inductively coupled plasma mass spectrometry (ICP-MS) experiments, however, revealed dissolution onset at only 1.05 V_RHE. In this manuscript, the apparent discrepancy is addressed by investigating bulk and nanoparticulated catalysts. It is shown that, given enough time for accumulation, traces of platinum can be detected at potentials as low as 0.85 V_RHE. At these low potentials, anodic dissolution is the dominant process, whereas, at more positive potentials, more platinum dissolves during the oxide reduction after accumulation. Interestingly, the potential and time dissolution dependence is similar for both types of electrode. Dissolution processes are discussed with relevance to fuel-cell operation and plausible dissolution mechanisms are considered.