Size-Dependent Selectivity of Iron-Based Electrocatalysts for electrochemical CO2 reduction

Applying non-precious metal catalysts to electrocatalytic CO2 reduction (CO2RR) to CO efficiently, rather than gold-based nanomaterials, is of practical significance. Here, we adopt zeolitic imidazolate frameworks (ZIFs) to assist the...

Composite chitosan and quaternary ammonium modified nanofibrillar cellulose anion exchange membranes for direct ethanol fuel cell applications

Fuel cells are a promising technology for energy production, but their commercialization is hindered mainly due to high costs. Direct alkaline ethanol fuel cells (DAFC) are receiving increasing attention as they can utilize cheaper, non-precious metal catalysts. A vital component of a DAFC is the anion exchange membrane (AEM). Currently, the commercially available AEMs don’t possess satisfactory properties. This indicates a need for the development of new highly efficient, environmentally friendly, and economically viable AEMs. Synthesis of synthetic polymer AEMs is usually complex and time-consuming, as well as environmentally unfriendly. Therefore, it is highly desired that the membrane material is bio-renewable, non-toxic and environmentally benign. In this work, a series of biopolymer membranes were designed by a simple, cost-effective, dispersion-casting procedure, fully complying with green-chemistry principles. Design of experiments was used as a methodology for identifying optimal combinations of influencing factors and their relations within selected responses. The obtained chitosan-Mg(OH)2 composite membranes containing modified nanofibrillar cellulose (CNF) fillers with quaternary ammonium groups were investigated for their mechanical properties, swelling ratio, ethanol permeability and ion exchange properties. Obtained data suggest the applicability of newly prepared, biopolymeric composites as eco-friendly AEMs in DAFC technologies.

Production of green hydrogen by efficient and economic electrolysis of water with super-alloy nanowire type electrocatalysts

Green hydrogen production from the electrolysis of water has good application prospect due to its renewability. The applied voltage of 1.6-2.2V isrequired in the traditional actual water electrolysis process although the the oretical decomposition potential of electrolyzing water is 1.23V. The high overpotential in the electrode reaction results in the high energy-consuming for the water electrolysis processes. The overpotentials of the traditional Ru, Ir and Pt based electrocatalysts are respectively 0.3V, 0.4V and 0.5V, furthermore use of the Pt, Ir and Ru precious metal catalysts also result in high cost of the water electrolysis process. For minimizing the overpoten tials in water electrolysis, a novel super-alloy nanowire electrocatalysts have been discovered and developed for water splitting in the present pa per. It is of significance that the overpotential for the water electrolysis on the super-alloy nanowire electrocatalyst is almost zero. The actual voltage required in the electrolysis process is reduced to 1.3V by using the novel electrocatalyst system with zero overpotential. The utilization of the super-alloy nanowire type electrocatalyst instead of the traditional Pt, Ir and Ru precious metal catalysts is the solution to reduce energy consumption and capital cost in water electrolysis to generate hydrogen and oxygen.

Electronic regulation of Ni single atom by confined Ni nanoparticles for fast and energy-efficient CO2 electroreduction

Electrocatalytic CO2 to CO conversion is approaching the industrial benchmark. Currently, Au electrodes show the best performance, whereas non-precious metal catalysts exhibit inferior activity. Here we show a densely populated Ni single-atom on nanoparticle catalyst (NiSA/NP) via direct solid-sate pyrolysis, where Ni nanoparticles donate electrons to Ni(i)-N-C sites via carbon nanotubes network, achieves a high CO current of 352 mA cm−2 at -0.55 V vs RHE in an alkaline flow cell. When coupled with a NiFe-based oxygen evolution anode into a zero-gap membrane electrolyser, it delivers an industrial-relevant CO current of 310 mA cm−2 at a low cell voltage of -2.3 V, corresponding to an overall energy efficiency of 57%. The superior CO2 electroreduction performance is attributed to the enhanced adsorption of key intermediate COOH* on electron-rich Ni single atom, together with the dense active sites.

Surfactant-Free Precious Metal Colloidal Nanoparticles for Catalysis

Colloidal syntheses of nanoparticles (NPs) are one of the preferred approaches to prepare precious metal catalysts. Unfortunately, most colloidal syntheses developed require stabilizing agents to avoid NP agglomeration and/or control NP size and morphology. While these surfactants can bring positive features, they typically block catalytically active sites on the NP surface. As a consequence, these additives often need to be removed by energy and/or time consuming steps, at the risk of complicating the synthesis, introducing irreproducibility and negatively altering the structure and properties of the prepared catalysts. Fortunately, several surfactant-free colloidal syntheses have been reported and are being developed. This Mini Review addresses the challenges in defining a surfactant-free colloidal synthesis of NPs and survey established and emerging strategies to obtain surfactant-free colloidal precious metal NPs. A focus is given to approaches that show promising features to bridge the gap between fundamental and applied research towards industrial applications.

Intramolecular Oxidative Diaryl Coupling of Tetrasubstituted Diphenylamines for Preparation of Bis(trifluoromethyl) Dimethyl Carbazoles

Synthetic preparation of carbazoles can be challenging, requiring ring building strategies and/or precious metal catalysts. Presented herein is a method for preparation of carbazoles with the use of inexpensive and reliable hypervalent iodine chemistry. An oxidative single electron transfer (SET) event initiates cyclization for preparation of our trifluoromethyl carbazoles. This method has been shown to be useful for a variety of bis(trifluoromethyl)carbazole isomers that are of primary interest for use as battery materials.

Electronic regulation of Ni single atom by confined Ni nanoparticles for fast and energy-efficient CO2 electroreduction

Electrocatalytic CO2 to CO conversion is approaching the industrial benchmark. Currently, Au electrodes show the best performance, whereas non-precious metal catalysts exhibit inferior activity. Here we show a densely populated Ni single-atom on nanoparticle catalyst (NiSA/NP) via direct solid-sate pyrolysis, where Ni nanoparticles donate electrons to Ni(i)-N-C sites via carbon nanotubes network, achieves a high CO current of 352 mA cm− 2 at -0.55 V vs RHE in an alkaline flow cell. When coupled with a NiFe-based oxygen evolution anode into a zero-gap membrane electrolyser, it delivers an industrial-relevant CO current of 310 mA cm− 2 at a low cell voltage of -2.3 V, corresponding to an overall energy efficiency of 57%. The superior CO2 electroreduction performance is attributed to the enhanced adsorption of key intermediate COOH* on electron-rich Ni single atom, together with the dense active sites.