A thermostated cell for electrochemistry: minimising natural convection and investigating the role of evaporation and radiation

Metal organic framework-derived transition metal-doped CoSx nanocage for enhanced visible light-assisted methanol electrocatalytic oxidation

Designing noble metal-free anode catalysts for visible light-assisted direct methanol fuel cells still remains a significant challenge. In this study, combining the photocatalytic and electrocatalytic properties of CoSx, a visible light-assisted methanol electrocatalytic oxidation strategy was provided. Doping engineering was employed to adjust the electronic structure of CoSx and improve their photoassisted methanol electrocatalytic oxidation activity. Using ZIF-67 as precursor, transition metal-doped CoSx (M-CoSx, M = Zn, Cu, Ni, and Cd) nanocage was synthesized by cation exchange and L-cysteine-controlled etching. Cd doping not only widens the light adsorption to the visible region but also enhances the separation efficiency of photogenerated electron-hole pairs. The electrochemical and photochemical results indicated that the strong oxidative photogenerated hole, OH˙, and O2˙- are beneficial for methanol electrocatalytic oxidation. The synergistic electrocatalytic and photocatalytic effect will be a practical strategy for improving the methanol electrocatalytic oxidation activity of noble metal-free semiconductor catalysts.

Experimental Voltammetry Analyzed Using Artificial Intelligence: Thermodynamics and Kinetics of the Dissociation of Acetic Acid in Aqueous Solution

Artificial intelligence (AI) is used to quantitatively analyze the voltammetry of the reduction of acetic acid in aqueous solution generating thermodynamic and kinetic data. Specifically, the variation of the steady-state current for the reduction of protons at a platinum microelectrode as a function of the bulk concentration of acetic acid is recorded and analyzed giving data in close agreement with independent measurements, provided the AI is trained with accurate and precise knowledge of diffusion coefficients of acetic acid, acetate ions, and H⁺.

Voltammetric demonstration of thermally induced natural convection in aqueous solution

In electrochemical systems imperfect thermostating inevitably leads to the presence of bulk convective flows. As recognised by Nernst [Z. Phys. Chem., 1904, 52] damping of these bulk convective flows next to a solid surface, or at the electrode, leads to diffusional mass transport predominating locally. This work questions the exclusivity of diffusional transport and provides hitherto unexplored physical insights into how thermally induced flows in bulk solution can, on both macro- and microelectrodes, influence a voltammetric measurement. Imperfect thermostating results in flows in the bulk solution which are predicted and here expeimentally shown to be of the order of 100 μm s-1. Here we show that even in the absence of natural convective flows induced by the electrochemical reaction itself, this thermally induced bulk convection can significantly affect the voltammetric response. First, evaporative losses from an open electrochemical cell can be sufficient to produce convective flows that can alter the electrochemical response. Second, electrodes with various sizes and geometries have been investigated and experimental results evidence that the sensitivity of an electrode to these flows in bulk solution is to a large extent controlled by the size of the surrounding non-conductive supporting substrate used to insulate parts of the electrode.

Silver Nanoparticle Detection in Real-World Environments via Particle Impact Electrochemistry

Silver nanoparticles (AgNPs) suspended in bottled mineral water and in tap water were successfully detected via the nanoimpact method without the deliberate addition of electrolyte. The recorded spike charge was used to indicate the stability of the AgNPs in their suspensions. It is found that the AgNPs largely agglomerated in potable water within the first 20 min. Addition of high concentrations of citrate (>2 mM) improved the stability of the AgNPs and enabled the detection and sizing of the AgNPs monomers in these media. Aging of the potable water suspensions was independently confirmed via UV-vis spectroscopy, validating the electrochemical method for detecting nanoparticles in real-world media.