DECIPHERING AND COUNTERING FORMIC ACID PERMEABILITY IN ZERO-GAP ELECTROLYZERS.

In recent years, formic acid (FA) has garnered attention as a compelling molecule for various chemical and everyday applications Additionally, with recent studies demonstrating direct FA generation through CO2 electrolysis, it can serve as a stable liquid hydrogen carrier. Nevertheless, FA-permeability via semi-permeable ion‑exchange membranes (FA-crossover) still constitutes a major issue in scalable polymer-electrolyte separated zero-gap electrolyzers, limiting the breakthrough of the technology to the larger-scale. Herein we present a holistic route towards understanding the mechanism of FA-crossover in zero-gap cells.

A terpyridine-based copper complex for electrochemical reduction of nitrite to nitric oxide.

In biological systems, nitrite reductase enzymes (NIRs) are responsible for reduction of nitrite (NO) to nitric oxide (NO). These NIRs have mostly Cu- or Fe-containing active sites, surrounded by amine-containing ligands. Therefore, mononuclear Cu complexes with N-donor ligands are highly relevant in the development of NIR model systems and in the mechanistic investigation of the nitrite reduction reaction.

An Electrochemical Screening Reactor Kit for Rapid Optimization of Electrosynthesis Applications.

Electrosynthetic processes powered by renewable energy present a viable solution to decarbonize the chemical industry, while producing essential chemical products for modern society. However, replacing well-established thermocatalytic methods with renewable-powered electrosynthesis requires cost-efficient and highly optimized systems. Current optimization of electrolysis conditions towards industrial applications involving scalable electrodes is time-consuming, highlighting the necessity for the development of electrochemical setups aimed at rapid and material efficient testing.

Unlocking the Activity of Molecular Assemblies for CO Electroreduction in Zero-Gap Electrolysers via Catalyst Ink Engineering.

In recent years, CO electrolysis, particularly the electrochemical reduction of CO to CO in zero-gap systems, has gained significant attention. While Ag-coated gas diffusion electrodes are commonly used in state-of-the-art systems, heterogenized molecular catalysts like bis-coordinated homoleptic silver(I) N,N-bis(arylimino)-acenaphthene (Ag-BIAN) complexes are emerging as a promising alternative due to their tunability and high mass activity. In this study, the influence of ink composition on the performance of Ag-BIAN-based GDEs in zero-gap electrolyzers (ZGEs) are systematically explored at 60 °C and 600 mA cm⁻.

Insights into the Electrochemical CORR Performance and Binding of Small Molecules on Quaternary Thiospinels AgFeSnS and CuFeSnS.

Using a mechanical synthesis method in the form of ball milling and an additional annealing step, a novel and accelerated route for the synthesis of the thiospinels toyohaite (AgFeSnS) and rhodostannite (CuFeSnS) was discovered. Both thiospinels display faradaic efficiencies of up to 73% for CO reduction to CO using an organic electrolyte in an H-type cell. The materials were furthermore implemented in a zero-gap electrolyzer, with toyohaite producing 22% CO and 52% H at 100 mA cm and rhodostannite 28% CO and 37% H.

Electroplated Electrodes for Continuous and Mass-Efficient Electrochemical Hydrogenation.

Electrocatalytic hydrogenations (ECH) enable the reduction of organic substrates upon usage of electric current and present a sustainable alternative to conventional processes if green electricity is used. Opposed to most current protocols for electrode preparation, this work presents a one-step binder- and additive-free production of silver- and copper-electroplated electrodes. Controlled adjustment of the preparation parameters allows for the tuning of catalyst morphology and its electrochemical properties.

Mechanochemical one-pot synthesis of heterostructured pentlandite-carbon composites for the hydrogen evolution reaction.

We have utilized carbon sources as milling additives to enable a direct mechanochemical one-pot synthesis of FeCoNiS/carbon (Pn/C) materials using elemental reaction mixtures. The obtained Pn/C materials are thoroughly characterized and their carbon content could be adjusted up to 50 wt%. In addition to carbon black (CB) as an additive, Pn/C materials were produced using graphite, reduced graphene oxide (rGO), and carbon nanotubes (CNTs), which allows the overall physicochemical properties of materials for energy storage applications to be adjusted.

Developing electrochemical hydrogenation towards industrial application.

Electrochemical hydrogenation reactions gained significant attention as a sustainable and efficient alternative to conventional thermocatalytic hydrogenations. This tutorial review provides a comprehensive overview of the basic principles, the practical application, and recent advances of electrochemical hydrogenation reactions, with a particular emphasis on the translation of these reactions from lab-scale to industrial applications. Giving an overview on the vast amount of conceivable organic substrates and tested catalysts, we highlight the challenges associated with upscaling electrochemical hydrogenations, such as mass transfer limitations and reactor design.

Trimetallic Pentlandites (Fe,Co,Ni)S for the Electrocatalytical HER in Acidic Media.

Recently, pentlandite materials have been shown to exhibit promising properties with respect to the hydrogen evolution reaction (HER). A whole series of trimetallic FeCoNi-pentlandite materials and composites have been synthesized from the elements using high-temperature synthesis and categorized in terms of purity. Furthermore, the electrocatalytic properties regarding the HER were determined and correlated to hydrogen adsorption energies, which were determined by means of density functional theory (DFT) calculations.

Synthesis and Characterization of Phosphorus-Containing Isocyclam Macrocycles and Their Nickel Complexes.

The tetradentate azamacrocycle cyclam (=1,4,8,11-tetraazacyclotetradecane) was studied profoundly for the coordination of transition metal ions, and the resulting complexes were investigated extensively for their catalytic performance in, e.g., O activation and electrocatalytic CO reduction.

Opening the pathway towards a scalable electrochemical semi-hydrogenation of alkynols earth-abundant metal chalcogenides.

Electrosynthetic methods are crucial for a future sustainable transformation of the chemical industry. Being an integral part of many synthetic pathways, the electrification of hydrogenation reactions gained increasing interest in recent years. However, for the large-scale industrial application of electrochemical hydrogenations, low-resistance zero-gap electrolysers operating at high current densities and high substrate concentrations, ideally applying noble-metal-free catalyst systems, are required.

Boosting the overall electrochemical water splitting performance of pentlandites through non-metallic heteroatom incorporation.

We report on synthesis of the heterotrimetallic pentlandite-type material FeCoNiS (FCNS) in presence of suitable phosphorus-(FCNSP) and nitrogen-(FCNSN) donors for the overall electrochemical water splitting. Throughout the experiments, a preferential incorporation of N into the FCNS-lattice is observed whereas the addition of phosphorus generally leads to metal-phosphate-FCNS composites. The obtained FCNSP, FCNSN, and FCNSNP facilitate the oxygen evolution reaction (OER) at 100 mAcm in 1.

Electrochemical CO reduction toward multicarbon alcohols - The microscopic world of catalysts & process conditions.

Tackling climate change is one of the undoubtedly most important challenges at the present time. This review deals mainly with the chemical aspects of the current status for converting the greenhouse gas CO via electrochemical CO reduction reaction (CORR) to multicarbon alcohols as valuable products. Feasible reaction routes are presented, as well as catalyst synthesis methods such as electrodeposition, precipitation, or sputtering.

Electrochemical CO reduction - The macroscopic world of electrode design, reactor concepts & economic aspects.

For the efficient electrochemical conversion of CO into valuable chemical feedstocks, a well-coordinated interaction of all electrolyzer compartments is required. In addition to the catalyst, whose role is described in detail in the part "Electrochemical CO Reduction toward Multicarbon Alcohols - The Microscopic World of Catalysts & Process Conditions" of this divided review, the general cell setups, design and manufacture of the electrodes, membranes used, and process parameters must be optimally matched. The authors' goal is to provide a comprehensive review of the current literature on how these aspects affect the overall performance of CO electrolysis.

An asymmetric cryptand for the site-specific coordination of 3d metals in multiple oxidation states.

Bis-tren (tren = tris(2-aminoethyl)amine) azacryptands were previously studied profoundly for the coordination of two +II metals and subsequent binding of substrates within their cavity. Likewise, cryptates including metals in different oxidations states were reported with the rather unstable hexa-imine analogues but also revealed only little stability. In this work, we report the synthesis of an asymmetric hexa-amine cryptand analogue by selectively exchanging three of the secondary amines of one binding site with sulphur atoms.

Crossing the Valley of Death: From Fundamental to Applied Research in Electrolysis.

The growing societal and political focus on the use of environmentally friendly technologies has led to an ever-increasing interest in electrolysis technologies in the scientific communities. This development is reflected by the plethora of candidate catalysts for the hydrogen and oxygen evolution reactions, as well as the CO reduction reaction, reported in the literature. However, almost none of them entered the stage of application yet.

Sustainable and rapid preparation of nanosized Fe/Ni-pentlandite particles by mechanochemistry.

In recent years, metal-rich sulfides of the pentlandite type (MS) have attracted considerable attention for energy storage applications. However, common synthetic routes towards pentlandites either involve energy intensive high temperature procedures or solvothermal methods with specialized precursors and non-sustainable organic solvents. Herein, we demonstrate that ball milling is a simple and efficient method to synthesize nanosized bimetallic pentlandite particles (FeNiS, Pn) with an average size of 250 nm in a single synthetic step from elemental- or sulfidic mixtures.

Unveiling Luminescent Ir and Rh N-Heterocyclic Carbene Complexes: Structure, Photophysical Specifics, and Cellular Localization in the Endoplasmic Reticulum.

Complexes of Rh and Ir of the [M(COD)(NHC)X] type (where M=Rh or Ir, COD=1,5-cyclooctadiene, NHC=N-heterocyclic carbene, and X=halide) have recently shown promising cytotoxic activities against several cancer cell lines. Initial mechanism of action studies provided some knowledge about their interaction with DNA and proteins. However, information about their cellular localization remains scarce owing to luminescence quenching within this complex type.

[FeFe]-Hydrogenases: maturation and reactivity of enzymatic systems and overview of biomimetic models.

While hydrogen plays an ever-increasing role in modern society, nature has utilized hydrogen since a very long time as an energy carrier and storage molecule. Among the enzymatic systems that metabolise hydrogen, [FeFe]-hydrogenases are one of the most powerful systems to perform this conversion. In this light, we will herein present an overview on developments in [FeFe]-hydrogenase research with a strong focus on synthetic mimics and their application within the native enzymatic environment.

Enhancing the CO Electroreduction of Fe/Ni-Pentlandite Catalysts by S/Se Exchange.

The electrochemical reduction of CO is an attractive strategy towards the mitigation of environmental pollution and production of bulk chemicals as well as fuels by renewables. The bimetallic sulfide Fe Ni S (pentlandite) was recently reported as a cheap and robust catalyst for electrochemical water splitting, as well as for CO reduction with a solvent-dependent product selectivity. Inspired by numerous reports on monometallic sulfoselenides and selenides revealing higher catalytic activity for the CO reduction reaction (CO RR) than their sulfide counterparts, the authors investigated the influence of stepwise S/Se exchange in seleno-pentlandites Fe Ni S Se (Y=1-5) and their ability to act as CO reducing catalysts.

Seleno-analogues of pentlandites (FeNiSSe, Y = 1-6): tuning bulk Fe/Ni sulphoselenides for hydrogen evolution.

We herein present a series of hitherto unprecedented seleno-pentlandites (Fe4.5Ni4.5S8-YSeY).

FeNiS (x = 3-6) as potential photocatalysts for solar-driven hydrogen production?

The efficient reduction of protons by non-noble metals under mild conditions is a challenge for our modern society. Nature utilises hydrogenases, enzymatic machineries that comprise iron- and nickel- containing active sites, to perform the conversion of protons to hydrogen. We herein report a straightforward synthetic pathway towards well-defined particles of the bio-inspired material FexNi9-xS8, a structural and functional analogue of hydrogenase metal sulfur clusters.

Bio-inspired design: bulk iron-nickel sulfide allows for efficient solvent-dependent CO reduction.

The electrocatalytic reduction of carbon dioxide (CORR) to valuable bulk chemicals is set to become a vital factor in the prevention of environmental pollution and the selective storage of sustainable energy. Inspired by structural analogues to the active site of the enzyme CODH, we envisioned that bulk Fe/Ni sulfides would enable the efficient reduction of CO. By careful adjustment of the process conditions, we demonstrate that pentlandite (FeNiS) electrodes, in addition to HER, also support the CORR reaching a peak faradaic efficiency of 87% and 13% for the formation of CO and methane, respectively at 3 mA cm.

Ru(ii)-Peptide bioconjugates with the cppH linker (cppH = 2-(2'-pyridyl)pyrimidine-4-carboxylic acid): synthesis, structural characterization, and different stereochemical features between organic and aqueous solvents.

Three new Ru(ii) bioconjugates with the C-terminal hexapeptide sequence of neurotensin, RRPYIL, namely trans,cis-RuCl2(CO)2(cppH-RRPYIL-κNp) (7), [Ru([9]aneS3)(cppH-RRPYIL-κNp)(PTA)](Cl)2 (8), and [Ru([9]aneS3)Cl(cppH-RRPYIL-κNp)]Cl (11), where cppH is the asymmetric linker 2-(2'-pyridyl)pyrimidine-4-carboxylic acid, were prepared in pure form and structurally characterized in solution. The cppH linker is capable of forming stereoisomers (i.e.