Operando-informed precatalyst programming towards reliable high-current-density electrolysis.

Electrocatalysts support crucial industrial processes and emerging decarbonization technologies, but their design is hindered by structural and compositional changes during operation, especially at application-relevant current densities. Here we use operando X-ray spectroscopy and modelling to track, and eventually direct, the reconstruction of iron sulfides and oxides for the oxygen evolution reaction. We show that inappropriate activation protocols lead to uncontrollable Fe oxidation and irreversible catalyst degradation, compromising stability and reliability and precluding predictive design.

Facile and Green Synthesis of Well-Defined Nanocrystal Oxygen Evolution Catalysts by Rational Crystallization Regulation.

The development of catalysts for an economical and efficient oxygen evolution reaction (OER) is critical for clean and sustainable energy storage and conversion. Nickel-iron-based (NiFe) nanostructures are widely investigated as active OER catalysts and especially shape-controlled nanocrystals exhibit optimized surface structure and electronic properties. However, the structural control from amorphous to well-defined crystals is usually time-consuming and requires multiple stages.

Miniaturized Carbon Fiber Paper Electrodes for In Situ High Resolution NMR Analyses.

Combining spectroscopic techniques with electrochemistry is a promising strategy, as it allows the detailed investigation of the species that are consumed and produced by the reaction in real time. However, as with any in situ coupling technique, the junction between NMR and electrochemistry presents some challenges, notably the distortion of NMR signals due to the placement of electrodes close to or within the detection region. In this work, miniaturized electrodes made of carbon fiber paper were developed and later modified with platinum.

Composite Graphite-Epoxy Electrodes for In Situ Electrochemistry Coupling with High Resolution NMR.

The in situ coupling between electrochemistry and spectrometric techniques can help in the identification and quantification of the compounds produced and consumed during electrochemical reactions. The combination of electrochemistry with nuclear magnetic resonance is quite attractive in this respect, but it has some challenges to be addressed, namely, the reduction in the quality of the NMR signal when the metallic electrodes are placed close to or in the detection region. Since NMR is not a passive technique, the convective effect of the magnetic force (magnetoelectrolysis), which acts by mixing the solution and increasing the mass transport, has to be considered.

In-situ MRI velocimetry of the magnetohydrodynamic effect in electrochemical cells.

Electrochemical reactions have become increasingly important in a large number of processes and applications. The use of NMR (Nuclear Magnetic Resonance) techniques to follow in situ electrochemistry processes has been gaining increasing attention from the scientific community because they allow the identification and quantification of the products and reagents, whereas electrochemistry measurements alone are not able to do so. However, when an electrochemical reaction is performed in situ the reaction rate can be increased by action of the Lorentz force, which is equal to the cross product between the current density and the magnetic field applied.

Strong magnetoelectrolysis effect during electrochemical reaction monitored in situ by high-resolution NMR spectroscopy.

The strong effect of magnetic field on the electrochemical (EC) reduction of a diamagnetic species was monitored in situ in a 600 MHz (14 T) NMR spectrometer. Throughout EC-NMR experiments, the diamagnetic species is influenced by the Lorentz force (cross product of current density and magnetic field), which in turn acts on analyte transport and, as a result, enhances reaction rates. This phenomenon, known as magnetoelectrolysis, has not been considered in several in situ EC-NMR studies in solution, electron paramagnetic resonance (EC-EPR) spectroscopy, and magnetic resonance imaging (EC-MRI) involving the oxidation and reduction of organic compounds and lithium ion batteries.

Use of the Relaxometry Technique for Quantification of Paramagnetic Ions in Aqueous Solutions and a Comparison with Other Analytical Methods.

We have demonstrated that the relaxometry technique is very efficient to quantify paramagnetic ions during in situ electrolysis measurements. Therefore, the goal of this work was to validate the relaxometry technique in the determination of the concentration of the ions contained in electrolytic solutions, Cu(2+), Ni(2+), Cr(3+), and Mn(2+), and compare it with other analytical methods. Two different NMR spectrometers were used: a commercial spectrometer with a homogeneous magnetic field and a home-built unilateral sensor with an inhomogeneous magnetic field.

In situ study of the magnetoelectrolysis phenomenon during copper electrodeposition using time domain NMR relaxometry.

Although the effect of magnetic field (B) on electrochemical reactions (magnetoelectrolysis phenomenon) has been long known, it has not been considered in electrochemical reactions analyzed in situ by magnetic resonance methods, such as nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), and magnetic resonance imaging (MRI), which are intrinsically performed in the presence of B. In this report, the effect of B on the copper electrodeposition reaction, measured by a low-field (0.23 T) NMR spectrometer, was demonstrated.