Electrochemical converters (electrolyzers, fuel cells, and batteries) have gained prominence during the last decade for the unavoidable energy transition and the sustainable synthesis of platform ...chemicals. One of the key elements of these systems is the electrode material on which the electrochemical reactions occur, and therefore its design will impact their performance. This review focuses on the electrospinning method by examining a number of features of experimental conditions. Electrospinning is a fiber-spinning technology used to produce three-dimensional and ultrafine fibers with tunable diameters and lengths. The thermal treatment and the different analyses are discussed to understand the changes in the polymer to create usable electrode materials. Electrospun fibers have unique properties such as high surface area, high porosity, tunable surface properties, and low cost, among others. Furthermore, a little introduction to the 5-hydroxymethylfurfural (HMF) electrooxidation coupled to H2 production was included to show the benefit of upgrading biomass derivates in electrolyzers. Indeed, environmental and geopolitical constraints lead to shifts towards organic/inorganic electrosynthesis, which allows for one to dispense with polluting, toxic and expensive reagents. The electrooxidation of HMF instead of water (OER, oxygen evolution reaction) in an electrolyzer can be elegantly controlled to electro-synthesize added-value organic chemicals while lowering the required energy for CO2-free H2 production.
Glycerol is a cheap, non‐toxic, and renewable by‐product of the rapid expansion of biodiesel and soap producers around the world. Glycerol electroforming is a method of oxidizing glycerol into ...valuable chemicals of interest to the pharmaceutical, cosmetics, polymer, and food industries. One of the technologies that have been studied over the past decades is to couple glycerol oxidation with the production of pure hydrogen in an electrolysis cell (so‐called electrolyzer), which has shown the advantage of consuming a much lower theoretical amount of electricity than conventional water electrolysis. The efficiency of this device is influenced by the nature, structure, and composition of the electrode material. This mini‐review concerns the understanding of glycerol electro‐oxidation, a brief state of the art of nanomaterials currently used to prepare electrode materials, and some results concerning the performance of electrolyzers in alkaline conditions that combine the efficient production of value‐added chemicals and hydrogen.
Glycerol electrooxidation reaction has been investigated by electrochemical, spectroelectrochemical, and chromatographic methods on palladium–nickel and palladium–silver nanoparticules supported on ...carbon Vulcan XC 72R. These materials, prepared by the so-called “Bromide Anion Exchange” method, exhibited high activity toward the glycerol electrooxidation in alkaline medium showing furthermore an important shift of the onset potential toward low potential values. Electrolysis coupled with high-performance liquid chromatography (HPLC) and in situ Fourier transform infrared spectroscopy (FTIRS) measurements have been used to determine the various compounds generated in the oxidative conversion of this three hydroxyl groups carbon molecule. Some products with high added value such as glycerate and tartronate have been identified. In situ FTIRS results have furthermore shown the pH decrease in the thin layer near the electrode. These results will positively serve as guidelines for future works on the potential use of glycerol in fuel cell devices in a cogeneration of high value chemicals and energy process.
Display omitted
•Fast preparation of graphene nanosheets by one-pot radiolytic reduction of GO.•One-pot synthesis of graphene nanosheets supported Au-Pt-Pd nanoparticles.•Radiolysis enables to ...engineer highly active Metal/rGO nanocomposites.•Ternary Au50Pt25Pd25/rGO electrocatalyst is 5-fold higher effective than Pt/rGO.•Selective glucose oxidation reaction in a 2-electron process leads to gluconate.
We report a novel “one-pot”, convenient and efficient method based on radiolysis to synthesize gold-based nanoparticles finely dispersed on reduced graphene oxide (rGO) nanosheets obtained from reductive transformation of graphene oxide (GO). Extensive characterizations of the metal/rGO nanocomposites were performed and revealed that the optimized bimetallic Au90Pd10 and trimetallic Au50Pd25Pt25 materials were mostly nano-alloyed. Not only the multimetallic catalysts demonstrate high electrocatalytic performances towards glucose in alkaline medium, but they also surpass the majority of the reported noble metals based nanocatalysts. The spectroelectrochemical investigations have highlighted a 2-electron reaction process leading to gluconate, a high added-value chemical used in various industries. Definitely, the strategies developed herein pave new rational pathways for the design of effective anode catalysts for glucose-based electrochemical energy converters and the scalability in the catalyst composition opens up new avenues in the efficient application of graphene-based nanocomposites as promising electrode materials in the electrocatalysis of carbohydrates.
Given the limited access to freshwater compared to seawater, a growing interest surrounds the direct seawater electrolysis to produce hydrogen. However, we currently lack efficient electrocatalysts ...to selectively perform the oxygen evolution reaction (OER) over the oxidation of the chloride ions that are the main components of seawater. In this contribution, we report an engineering strategy to synthesize heterogeneous electrocatalysts by the simultaneous formation of separate chalcogenides of nickel (NiSx, x = 0, 2/3, 8/9, and 4/3) and cobalt (CoSx, x = 0 and 8/9) onto a carbon-nitrogen-sulfur nanostructured network. Specifically, the oxidative aniline polymerization in the presence of metallic cations was combined with the calcination to regulate the separate formation of various self-supported phases in order to target the multifunctional applicability as both hydrogen evolution reaction (HER) and OER in a simulated alkaline seawater. The OER’s metric current densities of 10 and 100 mA cm−2 were achieved at the bimetallic for only 1.60 and 1.63 VRHE, respectively. This high-performance was maintained in the electrolysis with a starting voltage of 1.6 V and satisfactory stability at 100 mA over 17 h. Our findings validate a high selectivity for OER of ~100%, which outperforms the previously reported data of 87–95%.
Environmental and energy concerns surrounding the use of fossil fuels are driving an increasingly rapid transition to sustainable and eco‐responsible processes. Electrochemical processes can provide ...the necessary sustainability and economic roadmap for storing intermittent and renewable electricity by synthesizing, in cogeneration electrolyzers, energy carriers and/or synthetic chemicals (hydrogen, ammonia, etc.) via flagship reduction reactions (hydrogen evolution reaction (HER), nitrogen reduction reaction (NRR), etc.). To balance the electrochemical process, these cathodic processes have long been coupled to the oxygen evolution reaction (OER), which ultimately consumes almost 90% of the energy input. Recent years have witnessed an overwhelming development of anode scenarios based on biomass substrates, because OER cannot be driven below a certain potential threshold, while organics are thermodynamically more favorable. Therefore, paired electrolysis, which refers to cases where electrochemical oxidation and reduction are desired, embraces the electrocatalysis community for the electrolytic production of hydrogen, ammonia, etc. (cathode side), in parallel with value‐added chemicals (anode side), all with a modest electricity input. The trade‐off is selectivity at relevant current densities. This review discusses, the progress, challenges, and potential of biomass‐fueled paired electrosynthesis of valuable chemicals and fuels. Fundamental principles, main biomass solubilization methods, and different scenarios for paired electrosynthesis are presented.
For the efficient utilization of renewable electrical energy in an electrolyzer, the anodic and cathodic reactions can play a crucial role in paired electrosynthesis systems. This review interrogated the current research progress and major challenges in combining biomass electrooxidation with reduction reactions, which can not only minimize energy consumption but also produce valuable chemicals and fuels (hydrogen, ammonia, etc.).
The breakthrough in water electrolysis technology for the sustainable production of H
, considered as a future fuel, is currently hampered by the development of tough electrocatalytic materials. We ...report a new strategy of fabricating conducting polymer-derived nanostructured materials to accelerate the electrocatalytic hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and water splitting. Extended physical (XRD, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX)) and electrochemical (cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS)) methods were merged to precisely characterize the as-synthesized iridium and ruthenium modified polyaniline (PANI) materials and interrogate their efficiency. The presence of Ir(+III) cations during polymerization leads to the formation of Ir metal nanoparticles, while Ru(+III) induces the formation of RuO
oxide nanoparticles by thermal treatment; they are therefore methods for the on-demand production of oxide or metal nanostructured electrocatalysts. The findings from using 0.5 M H
SO
highlight an ultrafast electrochemical kinetic of the material PANI-Ir for HER (36 - 0 = 36 mV overpotential to reach 10 mA cm
at 21 mV dec
), and of PANI-Ru for OER (1.47 - 1.23 = 240 mV overpotential to reach 10 mA cm
at 47 mV dec
), resulting in an efficient water splitting exactly at its thermoneutral cell voltage of 1.45 V, and satisfactory durability (96 h).
Palladium has exceptional affinity with hydrogen and the evolution of the surface of its nanomaterials prepared from chemical methods over time is still unclear. Here, the reducing agent effect on Pd ...nanomaterials and their long-term chemical stability were scrutinized by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The subsequent impact on the catalytic properties was examined using the electrochemical oxygen reduction reaction (ORR). We have discovered that the nature of the reducing agent has noteworthy effects on the final composition of Pd nanomaterials prepared from chemical methods. The surface state of the nanomaterials prepared by using sodium borohydride as reducing agent (Pd/C–NaBH
4
) is radically different from those obtained from
l
-ascorbic acid (Pd/C–AA). In addition to pure metal, two oxides were identified: PdO and PdO
x
(
x
> 1). XRD analysis has upheld the presence of PdO only in Pd/C–NaBH
4
, thus underpinning the conclusion that NaBH
4
has drastically changed the Pd structure. Furthermore, the reducing agent substantially affects the electrocatalytic properties. The ORR starts with enhanced kinetics (
E
> 1 V
vs.
RHE) by a 4-electron process, producing
p
(H
2
O
2
) < 0.5% associated with excellent durability over 5000 cycles. Both catalysts outperform all reported data for Pd electrocatalysts. The novelty of this work is combining
ex
/
in situ
XPS and XRD analyses together with ORR as a catalytic model. Overall, this work represents a clear development in our understanding of Pd affinity towards hydrogen and paves new ways for the successful synthesis of Pd-based nanomaterials free from hydrides and oxides, and having impressive catalytic activities.
The future of fuel cells that convert chemical energy to electricity relies mostly on the efficiency of oxygen reduction reaction (ORR) due to its sluggish kinetics. By effectively bypassing the use ...of organic surfactants, the postsynthesis steps for immobilization onto electrodes, catalytic ink preparation using binders, and the common problem of nanoparticles (NPs) detachment from the supports involved in traditional methodologies, we demonstrate a versatile electrodeposition method for growing anisotropic microstructures directly onto a three-dimensional (3D) carbon felt electrode, using platinum NPs as the elementary building blocks. The as-synthesized materials were extensively characterized by integrating methods of physical (thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, inductively coupled plasma, and X-ray photoelectron spectroscopy) and electroanalytical (voltammetry, electrochemical impedance spectrometry) chemistry to examine the intricate relationship of material-to-performance and select the best-performing electrocatalyst to be applied in the model reaction of ORR for its practical integration into a microbial fuel cell (MFC). A tightly optimized procedure enables decorating an electrochemically activated carbon felt electrode by 40–60 nm ultrathin 3D-interconnected platinum nanoarrays leading to a hierarchical framework of ca. 500 nm. Half-cell reactions reveal that the highly rough metallic surface exhibits improved activity and stability toward ORR (E onset ∼ 1.1 V vs reversible hydrogen electrode, p(HO2 –) < 0.1%) and the hydrogen evolution reaction (−10 mA cm–2 for only 75 mV overpotential). Owing to its unique features, the developed material showed distinguished performance as an air-breathing cathode in a garden compost MFC, exhibiting better current and faster power generation than those of its equivalent classical double chamber. The enhanced performance of the material obtained herein is explained by the absence of any organic surfactants on the surface of the nanoarrays, the good metal–support interaction, particular morphology of the nanoarrays, and the reduced aggregation/detachment of particles. It promises a radical improvement in current surface reactions and paves a new way toward electrodes with regulated surface roughness, allowing for their successful application in heterogeneous catalysis.
PDF
