Maestro-level AI-generated review, from RCS journal

Sustainable Energy Fuels, 2024, 8, 4429-4452, DOI: 10.1039/d4se01060d, from page 4442:

“In the captivating domain of electrochemical exploration, the platinum electrode assumes the spotlight. A meticulous cyclic voltammetry analysis at 550 °C, immersed in molten NaOH, unveils the nuanced interplay of redox peaks, symbolic of the reduction of a delicate oxide film enveloping the platinum wire’s surface.¹³⁵Fig. 3(D) presents the cyclic voltammograms from Ge et al.‘s study¹³⁵ employing platinum as the working electrode. Each peak narrates a unique story: the cathodic current peak C₁ signifies the poetic reduction of the oxide film; the captivating surge in cathodic current at C₂ (−0.4 V) unfolds a ballet of hydrogen gas evolution; the anodic current peak O₁ depicts the stoic oxidation of the oxide film, and the enchanting O₂ serves as a crescendo harmonizing with the birth of oxygen gas. The saga continues beyond platinum, venturing into the realm of noble nickel. Its cyclic voltammetry narrative in molten NaOH reveals a tapestry of redox peaks akin to its platinum counterpart. The cathodic sonnet at C₃ serenades the reduction of a wispy oxide film caressing the nickel surface. Meanwhile, the anodic peak O₃ resonates with the bold oxidation of the nickel wire in the molten embrace. However, a twist in potential scan limits between 0.3 V and 1.3 V dims the presence of O₃, creating an interlude where the generated nickel oxide films seek refuge from reduction in the first cycle.¹³⁵ Both platinum and nickel trace redox peaks in molten NaOH, a testament to the oxide tales etched on their surfaces. Yet, nuances emerge, with platinum showcasing distinctive choreography of reduction and oxidation peaks, while nickel pirouettes with reduction peaks for the oxide film and an ode to oxidation for the nickel wire. Specific potential ranges embellish each peak with uniqueness.

Enter Ge et al.,¹³⁵ pioneers in this symphony. Cyclic voltammetry, the maestro’s baton, gracefully wielded on a platinum electrode basking in molten NaOH at 550 °C. A material chosen for its chemical steadfastness, platinum graced the stage with cyclic voltammograms. The cathodic reverie, C₁, whispers the reduction of a platinum-clad oxide film; O₁, anodic in nature, resounds oxidation. C₂‘s crescendo echoes the hydrogen evolution reaction, while O₂, a sonnet, harmonizes with the oxygen evolution reaction. The saga extends as Ge et al.¹³⁵ venture into the realms of platinum wire, a virtuoso in three molten hydroxides NaOH–KOH at 280 °C, LiOH–NaOH, and LiOH–KOH at 270 °C. In NaOH–KOH’s embrace, a cathodic crescendo at −0.32 V, a ballet of superoxide ions (O⁻²) reduction, unravelled. Cyclic voltammetry gracefully revealed the nuances of a platinum (Pt) electrode in a molten hydroxide electrolyte, a narrative skillfully crafted by Yang et al..¹⁰⁹ Reduction and oxidation peaks pirouetted elegantly at distinctive potentials, with reduction currents exhibiting their dance below −0.55 V. The stage was then seized by a commanding oxidation peak between −0.55 V and 0.1 V, rising dramatically above 0.17 V, where the evolution of oxygen took center stage.¹⁰⁹

In the presence of ammonia (NH₃), an ethereal onset potential of approximately −0.67 V marked the beginning of anodic currents, with a crescendo leading to a maximum of around −0.2 V. However, the drama unfolded swiftly above 0.15 V as oxygen evolution claimed the spotlight. The forward scan from −0.2 to 0.15 V witnessed a diminishing oxidation current, a subtle interplay involving Pt oxidation and the reduction of the active surface for ammonia oxidation. In a seamless transition, Yang et al.¹⁰⁹ continued their electrochemical tale, this time exploring the ammonia-driven drama on a platinum stage immersed in molten NaOH–KOH at 200 °C. Fig. 3(E) gracefully presented cyclic voltammograms, a visual symphony offering choices of argon and ammonia, while Ag stood as the stoic ref. 109. The dashed line served as a blank canvas, encapsulating platinum’s narrative in the hydroxide embrace, while the solid line painted the enchanting transformation of ammonia to N₂, all harmonized by the eutectic molten hydroxides. The platinum electrode, a versatile protagonist, showcased its prowess in every experiment, contributing a lyrical stanza to the grand saga of electrochemistry.”

https://pubs.rsc.org/en/content/articlelanding/2024/se/d4se01060d

Click to access drivel.pdf

(No-one obviously bothered to read this stuff before it got published – not even the authors…)

High strength hydrogen peroxide solution (64%)

50 % hydrogen peroxide is sold by Sigma-Aldrich (catalog # 516813) in the US. In many countries, it is not readily available because of the transport regulations. But it can be prepared from the common inexpensive 30 % grade quite easily, by concentrating 30% H2O2 on a rotovap with dry ice condenser, from ambient water bath, up to 60-65% H2O2 solution. The final concentration can be determined readily by proton NMR, in dry d6-DMSO, by integrating the hydrogen peroxide signal at 10.25 ppm against water signal at 3.5-3.6 ppm.

A commercial 31.8 % hydrogen peroxide solution 245.0 g [Aldrich 30-35%] was charged into a round bottom 0.5 L flask that has never been used for chemistry (the new flask was rinsed with D.I. water before use, to remove any dust particles). The hydrogen peroxide solution was then concentrated on a 25 C water bath at 10 mbar (full vacuum of Teflon piston pump) for about 2 hours. The liquid remaining in the flask, 109.65 g, was 64 % hydrogen peroxide by the NMR assay; this corresponds to a 90% theory yield.

This material should be stored in a clean 0.5 L amber bottle in a fridge, within a secondary container. Leave enough headspace in the flask, because overpressure can build up. 64% H2O2 solution has limited stability, it starts slowly producing visible bubbles of oxygen if left in a bottle at room temperature overnight. A small amount (few drops) of phosphoric acid or EDTA-2Na can be added as a stabilizer.