Single LiBH4 nanocrystal stochastic impacts at a micro water|ionic liquid interface

Abstract

LiBH4 is often employed as a reducing agent for metal nanoparticle (NP) preparation but is inherently a solid-state H2 hydrogen storage agent. Herein it is shown, through a combination of electron/optical microscopies and single entity electrochemical study, that LiBH4 is stored in the solid state within an ionic liquid (IL) as nanocrystals (NCs). The electrochemical monitoring of an immiscible water|IL (w|IL) micro-liquid|liquid interface (LLI) shows interfacial charge exchange associated with the stochastic impacts of single NCs. Meanwhile, in situ optical monitoring of a w|metal or w|IL interface shows that such impacts are associated with the development of a H2-in-IL micro/nano-foam related to the poor solubility of H2. Both the presence of solid NCs and the latter H2-in-IL foam suggest that H2 release from LiBH4-in-IL is a slow, but likely controlled process. The rate of H2 production at a macroscopic LLI is further confirmed by gas chromatographic measurements, in very good agreement with microscopic observations. The electrochemical LLI provides unique investigative access to LiBH4 NCs and offers insight into H2 storage in ILs, or for direct borohydride fuel cells, as well as NP synthesis. Highlights:1. Single entity electrochemical detection of LiBH4 nanocrystals at a water|ionic liquid interface.2. Single H2 bubble generated from LiBH4 nanocrystals inside an ionic liquid.3. LiBH4 induced H2-in-ionic liquid foam at water|ionic liquid interface.

Ionosomes: Observation of Ionic Bilayer Water Clusters

“…The sensing interface has evolved from the traditional metallic microelectrode/electrolyte interface to the micro-ITIES (Figure and Figures S1, S2 in the SI). − With a molecularly flat ITIES, a wide polarizable potential window (PPW) builds up and highly reproducible ion transfer signals can be observed (Figure S4, SI). Conducting SEE in all the above-cited works, at either the metallic microelectrode/electrolyte interface or the micro-ITIES, the analytes such as nanoparticles are often prepared in advance and then added into the electrolyte solution before testing.…”

Differentiating electrochemically active regions of indium tin oxide electrodes for hydrogen evolution and reductive decomposition reactions. An in situ optical microscopy approach

“…The approach proposed consists in triggering the HER at ITO electrode in micrometric electrolyte droplets, in a SECCM-like configuration [32], and visualizing and discriminating by optical microscopy the fingerprint of the two competing processes: either the formation of H 2 NBs or the formation of metallic NPs issued from the ITO electro-reduction. Label free optical microscopies [25,26,[33][34][35] relying on the visualization of light scattered by small objects, are indeed capable of imaging gas bubbles and NPs. The light scattering can be detected from the local variation in refractive index they produce upon their formation, by standard optical microscopy under dark field illumination [25,35], or by surface plasmon resonance [11,34,36,37] or interference reflection microscopies [26,38].…”

Faradaic Counter for Liposomes Loaded with Potassium, Sodium Ions, or Protonated Dopamine

“…Stockmann et al adopted the strategy of electrocatalytic amplification with oxygen reduction as the indicator reaction at the micro-ITIES to achieve the detection of single platinum nanoparticles. After that, this method was also extended to the observation of single LiBH 4 nanocrystal collisions . However, application of this platform in the detection of single liposomes has not yet been reported.…”