In‐Liquid Plasma Modified Nickel Foam: NiOOH/NiFeOOH Active Site Multiplication for Electrocatalytic Alcohol, Aldehyde, and Water Oxidation

Abstract

The oxygen evolution reaction (OER) and the value‐added oxidation of renewable organic substrates are critical to supply electrons and protons for the synthesis of sustainable fuels. To meet industrial requirements, new methods for a simple, fast, environmental‐friendly and cheap synthesis of robust, self‐supported and high surface area electrodes are required. Herein, a novel in‐liquid plasma (plasma electrolysis) approach for the growth of hierarchical nanostructures on nickel foam is reported on. Under morphology retention, iron can be doped into this high surface area electrode. For the oxidation of 5‐(hydroxymethyl)furfural and benzyl alcohol, the iron‐free, plasma‐treated electrode is more suitable reaching current densities up to 800 mA cm−2 with Faradaic efficiencies above 95%. For the OER, the iron‐doped nickel foam electrode reaches the industrially relevant current density of 500 mA cm−2 at 1.473 ± 0.013 VRHE (60 °C) and shows no activity decrease over 140 h. The different effects of iron doping are rationalized using methanol probing and in situ Raman spectroscopy. Furthermore, the intrinsic activity is separated from the number of active sites, and, for the organic oxidation reactions, diffusion limitations are revealed. The authors anticipate that the plasma modified nickel foam will be suitable for various (electro)catalytic processes.

Oxygen Evolution/Reduction Reaction Catalysts: From In Situ Monitoring and Reaction Mechanisms to Rational Design

“…Furthermore, the electrochemically derived Co oxyhydroxides can maintain a current density of 250 mA/cm –2 at 65 °C under neutral conditions over 1 month without a significant current decline. To further establish a simple and eco-friendly method for fabricating an electrode for industrial-scale O 2 production, the in-liquid plasma approach was applied to grow hierarchical NiOOH/FeOOH nanostructures on Ni foam . The elaborate OER electrode can easily reach an industrial-scale current density of 500 mA/cm 2 due to its high surface area and rich active sites.…”

“…To further establish a simple and eco-friendly method for fabricating an electrode for industrial-scale O 2 production, the in-liquid plasma approach was applied to grow hierarchical NiOOH/FeOOH nanostructures on Ni foam. 679 The elaborate OER electrode can easily reach an industrial-scale current density of 500 mA/cm 2 due to its high surface area and rich active sites.…”

New Avenues to Chemical Space for Energy Materials by the Molecular Precursor Approach

“…[51] However, OER is crucial to supply the necessary electrons and protons to produce H 2 at the counterpart. [52][53][54] The theoretical potential required for OER and HER are 1.23 and 0 V, respectively (at 25 °C in 1 atm pressure) to derive the OWS reaction. [55,56] Due to the sluggish kinetics of OER and HER, along with cell and catalyst resistances, in practice, an extra potential is required to drive these reactions to attain a set current density, which is called the overpotential (η).…”

Challenges for Hybrid Water Electrolysis to Replace the Oxygen Evolution Reaction on an Industrial Scale

“…Excellent and comprehensive reviews on hybrid water electrolysis have been published already, covering electrolyzer design, catalyst development, substrate variety, and mechanistic insights. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] In contrast to these previous reviews, in this perspective, we focus on the challenges of hybrid water electrolysis and answer the following questions: i. Why are the overpotentials required for organic substrate oxidation usually substantially larger than the ones required for the OER?…”