The study of the adsorption/desorption of acetate anions on a Pt(111) electrode and the effect of counter cations in acidic media

pKa as a Predictive Descriptor for Electrochemical Anion Adsorption

The adsorption of anions onto metal surfaces is important in many applications including effective (electro)catalyst design, metal surface modification, and contaminant removal in wastewater treatment. In electrocatalysis, anions can be both reactive intermediates or site-blocking spectators, where their adsorption strength therefore dictates the rate of reaction. In this work, we have measured the adsorption energy of a series of carboxylic acids on a Pt (111) single-crystal electrode surface from aqueous solution. We find that the adsorption strength of the carboxylate anion is linearly correlated with its acid-dissociation constant (pKa) and therefore the heterolytic O-H bond dissociation strength in solution. Using density functional theory modeling, we split the anion adsorption energy into a sum of the adsorption energy and electron affinity of a neutral (carboxyl) radical. Surprisingly, the adsorption energy of the carboxyl radicals are similar and therefore the large difference in electron affinity is what dictates anion adsorption strength; the greater the cost in energy to remove the electron from the anion upon adsorption, the weaker its binding. Therefore, at least within a class of anions with similar structure and surface binding atoms, both electron affinity and acidity are predictive descriptors of adsorption strength.

Adsorption of Acetate on Au(111): An in-situ Scanning Tunnelling Microscopy Study and Implications on Formic Acid Electrooxidation

The adsorption of acetate on an Au(111) electrode surface in contact with acetic acid at pH 2.7 was imaged in-situ using scanning tunnelling microscopy (STM). Two different ordered structures were imaged for acetate adsorbed in the bidentate configuration on the unreconstructed 1 × 1 surface at 0.95 V (vs. the saturated calomel electrode, SCE). The first structure, ( 19 × 19 ) R 23 . 45 ∘ , is metastable and transforms at constant potential within 20 minutes to a ( 2 × 2 ) structure, which is thermodynamically more favourable. The ( 2 × 2 ) acetate adlayer starts to form at step edges and propagates via nucleation and growth onto terraces. The findings from in-situ STM are in agreement with the electrochemical behaviour of acetate on Au(111) characterized by voltammetry. A comparison is made with formate adsorption on Au(111). While acetate is not reactive, in contrast to formate, it can act as a spectator species in formic acid electrooxidation.

Single-Particle Plasmon Voltammetry (spPV) for Detecting Anion Adsorption

Nanoparticle and thin film surface plasmons are highly sensitive to electrochemically induced dielectric changes. We exploited this sensitivity to detect reversible electrochemical potential-driven anion adsorption by developing single-particle plasmon voltammetry (spPV) using plasmonic nanoparticles. spPV was used to detect sulfate electroadsorption to individual Au nanoparticles. By comparing both semiconducting and metallic thin film substrates with Au nanoparticle monomers and dimers, we demonstrated that using Au film substrates improved the signal in detecting sulfate electroadsorption and desorption through adsorbate modulated thin film conductance. Using single-particle surface plasmon spectroscopic techniques, we constructed spPV to sense sulfate, acetate, and perchlorate adsorption on coupled Au nanoparticles. spPV extends dynamic spectroelectrochemical sensing to the single-nanoparticle level using both individual plasmon resonance modes and total scattering intensity fluctuations.

One-step anion-assisted electrodeposition of ZnO nanofibrous networks as photoanodes for dye-sensitized solar cells

An efficient ZnO photoanode consisting of nanofibrous networks for DSSCs was synthesized using a one-step electrodeposition in a solution containing Zn(NO₃)₂, KCl, NaCH₃COO, and Na₃C₆H₅O₇.

Mineralization of gaseous acetaldehyde by electrochemically generated Co(III) in H2SO4 with wet scrubber combinatorial system

Electrochemically generated Co(III) mediated catalytic room temperature incineration of acetaldehyde, which is one of volatile organic compounds (VOCs), combined with wet scrubbing system was developed and investigated. Depending on the electrolyte's type, absorption come removal efficiency is varied. In presence of electrogenerated Co(III) in sulfuric acid, acetaldehyde was mineralized to CO2 and not like only absorption in pure sulfuric acid. The Co(III) mediated catalytic incineration led to oxidative absorption and elimination to CO2, which was evidenced with titration, CO2, and cyclic voltammetric analyses. Experimental conditions, such as current density, concentration of mediator, and gas molar flow rate were optimized. By the optimization of the experimental conditions, the complete mineralization of acetaldehyde was realized at a room temperature using electrochemically generated Co(III) with wet scrubber combinatorial system.