Kinetics of the deuterium and hydrogen evolution reactions at palladium in alkaline solution

Influence of Water Contamination on the SEI Formation in Li-Ion Cells: An Operando EQCM-D Study

The interphase formation on carbon (C) anodes in LiPF₆/EC + DEC Li-ion battery electrolyte is analyzed by combining operando electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D) with in situ online electrochemical mass spectrometry (OEMS). EQCM-D enables unique insights into the anode solid electrolyte interphase (SEI) mass/thickness, its viscoelastic properties, and changes of electrolyte viscosity during the initial formation cycles. The interphase in the pure electrolyte is relatively soft (G'_SEI ≈ 0.2 MPa, η_SEI ≈ 10 mPa s) and changes its viscoelastic properties dynamically as a function of the electrode potential. With increasing electrolyte water content, the SEI becomes thicker and much more rigid. Doubly labeled D₂¹⁸O is added to the electrolyte in order to precisely track the reaction pathway of water at the anode by OEMS. In the first cycle between 2.6 and 1.7 V versus Li⁺/Li, water is reduced, and hydroxide ions initiate an autocatalytic hydrolysis of EC. With large amounts of water initially present in the electrolyte, most of the formed CO₂ gas is scavenged by reactions with hydroxide and alkoxide ions, forming a thick, rigid, and Li₂CO₃-rich early interphase on the C anode. This layer alleviates the following electrolyte decomposition processes and slows the reduction of EC < 1 V versus Li⁺/Li.

Controlled Micro/Nanodome Formation in Proton-Irradiated Bulk Transition-Metal Dichalcogenides

At the few-atom-thick limit, transition-metal dichalcogenides (TMDs) exhibit strongly interconnected structural and optoelectronic properties. The possibility to tailor the latter by controlling the former is expected to have a great impact on applied and fundamental research. As shown here, proton irradiation deeply affects the surface morphology of bulk TMD crystals. Protons penetrate the top layer, resulting in the production and progressive accumulation of molecular hydrogen in the first interlayer region. This leads to the blistering of one-monolayer thick domes, which stud the crystal surface and locally turn the dark bulk material into an efficient light emitter. The domes are stable (>2-year lifetime) and robust, and host strong, complex strain fields. Lithographic techniques provide a means to engineer the formation process so that the domes can be produced with well-ordered positions and sizes tunable from the nanometer to the micrometer scale, with important prospects for so far unattainable applications.

Electrochemical Growth of Metallic Nanoparticles onto Immobilized Polymer Brush Ionic Liquid as a Hybrid Electrocatalyst for the Hydrogen Evolution Reaction

Platinum and palladium are the first choice electrocatalysts to drive the hydrogen evolution reaction. In this report, surface modification was introduced as a potential approach to generate hybrid electrocatalyst. The immobilized polymer brush, poly(1-allyl-3-methylimidazolium) (PAMI), was used as a nanostructured template for guiding the electrochemical deposition of metallic nanoparticles (Pd, Pt). The intrinsic properties of the polymer brush in term of nanostructured architecture and the anions mobility within the polymer was exploited to generate a hybrid electrocatalyst. The latter was generated using two different approaches including the direct electrochemical deposition of Pd or Pt metal and the indirect approach through the anion exchange reaction followed by the electrochemical deposition under self-electrolytic conditions. The hybrid structure based on the polymer/metallic NP exhibits an enhancement of the catalytic performance toward hydrogen evolution reaction with a low Tafel slope and overpotential. Interestingly, the indirect approach leads to decrease the metal loading by two orders of magnitude, when compared to those generated in the absence of the polymeric layer, while retaining the electrocatalytic performance.

Electrochemically deposited palladium as a substrate for self-assembled monolayers

The vast majority of reports of self-assembled monolayers (SAMs) on metals focus on the use of gold. However, other metals, such as palladium, platinum, and silver offer advantages over gold as a substrate. In this work, palladium is electrochemically deposited from PdCl2 solutions on glassy carbon electrodes to form a substrate for alkanethiol SAMs. The conditions for deposition are optimized with respect to the electrolyte, pH, and electrochemical parameters. The palladium surfaces have been characterized by scanning electron microscopy (SEM) and the surface roughness has been estimated by chronocoulometry. SAMs of alkane thiols have been formed on the palladium surfaces, and their ability to suppress a Faradaic process is used as an indication for palladium coverage on the glassy carbon. The morphology of the Pd deposit as characterized by SEM and the blocking behavior of the SAM formed on deposited Pd delivers a consistent picture of the Pd surface. It has been clearly demonstrated that, via selection of experimental conditions for the electrochemical deposition, the morphology of the palladium surface and its ability to support SAMs can be controlled. The work will be applied to create a mixed monolayer of metals, which can subsequently be used to create a mixed SAM of a biocomponent and an alkanethiol for biosensing applications.