Electrochemical Activation of Ni-Fe Oxides for the Oxygen Evolution Reaction in Alkaline Media.

The oxygen evolution reaction (OER) is essential to many key electrochemical devices, including HO electrolyzers, CO electrolyzers, and metal-air batteries. NiFe oxides have been historically identified as active for the OER, though they have been less studied in their more commercially relevant bulk oxide forms, such as NiFeO. Past works have demonstrated that the initial starting phase of Ni-(Fe) precatalysts can influence their activation to the Ni-(Fe)-OOH active phase, including the rate and degree of conversion, pointing to the necessity of understanding activation protocols and in situ characteristics of catalyst materials at the device level.

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.

Fabrication and optimization of a multielectrode microfluidic electrochemical flow cell for fast and dynamic detection of reaction products.

Construction and experimental validation of electrochemical cells with multiple electrodes in a microfluidic channel is described. Details of the fabrication of the electrodes and polydimethylsiloxane channel using soft lithography methods are given. Calibration of the collection efficiencies and transit times between electrodes validate the use of these cells for fast electrochemical detection of soluble species.

Iron and Nickel Substituted Perovskite Cobaltites for Sustainable Oxygen Evolving Anodes in Alkaline Environment.

Perovskite oxides have great flexibility in their elemental composition, which is accompanied by large adjustability in their electronic properties. Herein, we synthesized twelve perovskite oxide-based catalysts for the oxygen evolution reaction (OER) in alkaline media. The catalysts are based on the parent oxide perovskite BaGdLaCoO (BGLC587) and are synthesized through the sol-gel citrate synthesis route.

Nickel Phosphide: The Effect of Phosphorus Content on the Activity and Stability toward Oxygen Evolution Reaction in Alkaline Medium.

In this work a systematic study of the effect of the metal to phosphorus ratio in Ni-P nanoparticles on their catalytic activity with respect to the OER is reported. To this end, nickel phosphide nanoparticles are synthesized through two different synthesis routes, one involving in-situ phosphidation and one involving ex-situ phosphidation. In-situ phosphidation is performed via two steps route in a one-pot synthesis, in which Ni nanoparticles are formed at 220 °C, but not isolated, and then transformed to phase-pure either NiP or NiP nanocrystallites.

Towards scaling up the sonochemical synthesis of Pt-nanocatalysts.

Large scale production of electrocatalysts for electrochemical energy conversion devices such as proton exchange membrane fuel cells must be developed to reduce their cost. The current chemical reduction methods used for this synthesis suffer from problems with achieving similar particle properties such as particle size and catalytic activity when scaling up the volume or the precursor concentration. The continuous production of reducing agents through the sonochemical synthesis method could help maintain the reducing conditions (and also the particle properties) upon increasing the reactor volume.

Stability of Ni-Fe-Layered Double Hydroxide Under Long-Term Operation in AEM Water Electrolysis.

Anion exchange membrane water electrolysis (AEMWE) is an attractive method for green hydrogen production. It allows the use of non-platinum group metal catalysts and can achieve performance comparable to proton exchange membrane water electrolyzers due to recent technological advances. While current systems already show high performances with available materials, research gaps remain in understanding electrode durability and degradation behavior.

In Situ Sonoactivation of Polycrystalline Ni for the Hydrogen Evolution Reaction in Alkaline Media.

In this investigation, we report on the development of a method for activating polycrystalline metallic nickel (Ni(poly)) surfaces toward the hydrogen evolution reaction (HER) in N-saturated 1.0 M KOH aqueous electrolyte through continuous and pulsed ultrasonication (24 kHz, 44 ± 1.40 W, 60% acoustic amplitude, ultrasonic horn).

Optimum scavenger concentrations for sonochemical nanoparticle synthesis.

Maintaining nanoparticle properties when scaling up a chemical synthesis is challenging due to the complex interplay between reducing agents and precursors. A sonochemical synthesis route does not require the addition of reducing agents as they are instead being continuously generated in-situ by ultrasonic cavitation throughout the reactor volume. To optimize the sonochemical synthesis of nanoparticles, understanding the role of radical scavengers is paramount.

Sonochemical Synthesis of Cu@Pt Bimetallic Nanoparticles.

Reducing the amount of noble metals in catalysts for electrochemical conversion devices is paramount if these devices are to be commercialized. Taking advantage of the high degree of particle property control displayed by the sonochemical method, we set out to synthesize Cu@Pt bimetallic nanocatalysts in an effort to improve the mass activity towards the hydrogen evolution reaction. At least 17 times higher mass activity was found for the carbon supported Cu@Pt bimetallic nanocatalyst (737 mA mg−1, E = −20 mV) compared to carbon supported Pt nanocatalysts prepared with the same ultrasound conditions (44 mA mg−1, E = −20 mV).

Sonoactivated polycrystalline Ni electrodes for alkaline oxygen evolution reaction.

The development of cost-effective and active water-splitting electrocatalysts is an essential step toward the realization of sustainable energy. Its success requires an intensive improvement in the kinetics of the anodic half-reaction of the oxygen evolution reaction (OER), which determines the overall system efficiency to a large extent. In this work, we designed a facile and one-route strategy to activate the surface of metallic nickel (Ni) for the OER in alkaline media by ultrasound (24 kHz, 44 W, 60% acoustic amplitude, ultrasonic horn).

Frequency controlled agglomeration of pt-nanoparticles in sonochemical synthesis.

Optimizing the surface area of nanoparticles is key to achieving high catalytic activities for electrochemical energy conversion devices. In this work, the frequency range (200 kHz-500 kHz) for maximum sonochemical radical formation was investigated for the sonochemical synthesis of Pt-nanoparticles to assess whether an optimum frequency exists or if the entire range provides reproducible particle properties. Through physical and electrochemical characterization, it was found that the frequency dependent mechanical effects of ultrasound resulted in smaller, more open agglomerates at lower frequencies with agglomerate sizes of (238 ± 4) nm at 210 kHz compared to (274 ± 2) nm at 326 kHz, and electrochemical surface areas of (12.

Effect of the Synthetic Method on the Properties of Ni-Based Hydrogen Oxidation Catalysts.

The latest progress in alkaline anion-exchange membranes has led to the expectation that less costly catalysts than those of the platinum-group metals may be used in anion-exchange membrane fuel cell devices. In this work, we compare structural properties and the catalytic activity for the hydrogen-oxidation reaction (HOR) for carbon-supported nanoparticles of Ni, NiCo, NiCu, and NiFe, synthesized by chemical and solvothermal reduction of metal precursors. The catalysts are well dispersed on the carbon support, with particle diameter in the order of 10 nm, and covered by a layer of oxides and hydroxides.

An in situ XAS study of high surface-area IrO produced by the polymeric precursor synthesis.

Iridium oxide powders with a surface area of more than 1 m g (4 m g from the H-UPD charge) and iridium-oxide crystallites less than 10 nm across were synthesized by heat treating gels formed from citric acid, ethylene glycol and dihydrogen hexachloroiridate(iv) in air. The characteristics of the resulting material was found to be strongly dependent on the heat-treatment step in the synthesis. A single heat-treatment of the gel resulted in a material with a substantial fraction of elemental iridium metal, i.

Renewable CO recycling and synthetic fuel production in a marine environment.

A massive reduction in CO emissions from fossil fuel burning is required to limit the extent of global warming. However, carbon-based liquid fuels will in the foreseeable future continue to be important energy storage media. We propose a combination of largely existing technologies to use solar energy to recycle atmospheric CO into a liquid fuel.

Strategies for the analysis of the elemental metal fraction of Ir and Ru oxides via XRD, XANES, and EXAFS.

Iridium and ruthenium oxide are active electrocatalysts for oxygen evolution. The relation between preparation method, structure, and behavior of mixed oxides of iridium and ruthenium are of interest in order to obtain active and stable catalysts. In this work the structure of mixed Ru-Ir oxides synthesized by the polymeric precursor method, which involves the formation of a gel containing the metal precursors and subsequent heat-treatment in air, was studied for the IrRuO system.