Organometallic Catalysts Research Articles

Synthesis and characterization of MgFe2O4@SiO2@CBCE-Pd as a novel, green organometallic catalyst, and study of its catalytic activity for C–C and C–O cross-coupling reactions

In this work, a new palladium nanocatalyst was supported on CBCE functionalized MNPs (MgFe2O4@SiO2@CBCE-Pd) and was characterized by EDS, FTIR, SEM, ICP, XRD, VSM, and TGA techniques. The performance of MgFe2O4@SiO2@CBCE-Pd was found to exhibit excellent catalytic activity for CO and C–C cross-coupling reactions. The nanocatalyst showed high activity and efficiency as evidenced by the excellent yields of products obtained from the C–O and CC coupling reaction. Additionally, the synthesized nanocatalyst can be retrieved using a magnet and employed for up to four cycles without diminishing its catalytic effectiveness.

Immobilization of cross-linked enzymes aggregates on hierarchical covalent organic frameworks: Highly stable chemoenzymatic nanoreactor for asymmetric synthesis of optically active halohydrins

Organometallic catalyst is extensively applied for the non-enzymatic regeneration of nicotinamide adenine dinucleotide (phosphate) cofactors, but suffering from the mutual inactivation with the enzymes in one pot. The spatially separated immobilization of organometallic catalyst and enzymes on suitable carriers not only can reduce their mutual inhabitation but also can enhance their reusability. Here in this work, we present a hierarchical porous COFs (HP-TpBpy) that incorporated with [(Cp*RhCl2]2 to generate the metalized COF, Rh-HP-TpBpy. The obtained Rh-HP-TpBpy exhibited superior performance in nicotinamide adenine dinucleotide (NADH) and nicotinamide adenine dinucleotide phosphate (NADPH) regeneration using formate as the hydride donor, significantly outperforming the natural formate dehydrogenases in cofactor preference toward NADP+. Subsequently, the Lactobacillus fermentum short-chain dehydrogenase/reductase 1 (LfSDR1) was then cross-linked into enzyme aggregates (CLEA) and immobilized on hierarchical Rh-HP-TpBpy, achieving the integrated chemoenzymatic catalyst, LfSDR1@Rh-HP-TpBpy, which can catalyze the chemoenzymatic reduction of halogenated aryl ketones and give the corresponding optically active halohydrins with high conversion and enantiomeric excess (ee) value up to 99 %. The LfSDR1@Rh-HP-TpBpy also exhibits largely enhanced stability compared with the free LfSDR1 and the CLEAs-LfSDR1, enabling its excellent reusability.

Organo-Mediated Ring-Opening Polymerization of Ethylene Brassylate from Cellulose Nanofibrils in Reactive Extrusion.

Ethylene brassylate is a renewable macrolactone from castor oil that can be polymerized via ring-opening polymerization (ROP) to obtain a fully biosourced biodegradable polyester. ROP mediated by organometallic catalysts leads to high molar mass poly(ethylene brassylate) (PEB). However, the use of metal-free organocatalysis has several advantages, such as the reduction of toxic and expensive metals. In this work, a novel cellulose nanofibril (CNF)/PEB nanocomposite fabrication process by organocatalysis and reactive extrusion (REx) is disclosed. Here, ROP was carried out via solvent-free REx in the presence of CNFs using organic 1,5,7-triazabicyclo[4.4.0]dec-5-ene as a catalyst. Neat or lactate-esterified CNFs (LACNF) were used as initiators to investigate the effect of surface topochemistry on the in situ polymerization and the properties of the nanocomposites. A molar mass of 9 kDa was achieved in the presence of both unmodified and LACNFs with high monomer conversion (>98%) after 30 min reaction in a microcompounder at 130 °C. Tensile analysis showed that both nanofibril types reinforce the matrix and increase its elasticity due to the efficient dispersion obtained through the grafting from polymerization achieved during the REx. Mechanical recycling of the neat polymer and the nanocomposites was proven as a circular solution for the materials' end-of-life and showed that lactate moieties induced some degradation.

Electrochemical Impedance of Well-Passivated Semiconductors Reveals Bandgaps, Fermi Levels, and Interfacial Density of States.

For well-passivated semiconductor materials, the density of states (DOS) at the band edge determines the concentration of electrons (or holes) available to participate in photo/electrochemical redox and chemical reactions. Electrochemical impedance enables the characterization of photo-electrode DOS in a functional, in situ, electrochemical environment. However, the in situ electrochemical approach remains underutilized for band structure characterization of inorganic semiconductors. In this work, we demonstrate that the DOS of the well-passivated, highly ordered semiconductors silicon and germanium is directly probed by electrochemical impedance spectroscopy (EIS). More specifically, EIS measurements of the chemical capacitance in contact with electrolyte enable direct analysis of the DOS properties. From the capacitance-potential plot, the following parameters can be extracted: Fermi level, valence band maximum, conduction band minimum, and a quantitative value of the number of states at each potential. This study aims to establish the groundwork for future EIS investigations of electronically modified semiconductor interfaces with covalently bound organic molecules, organometallic catalysts, or more complex biorelated functionalizations.

Efficiency and Mechanism of Catalytic Siloxane Exchange in Vitrimer Polymers: Modeling and Density Functional Theory Investigations.

Of late, siloxane-containing vitrimers have gained significant interest due to their fast dynamic characteristics over a reasonable temperature range (180-220 °C), making them well-suited for diverse applications. The exchange reaction pathway in the siloxane vitrimers is accountable for the covalent adaptive network, with the reaction's effectiveness being regulated by either organic or organometallic catalysts. However, directly studying the exchange reaction pathway in the bulk phase using experimental approaches is challenging because of the intricate and interconnected structure of these vitrimers. Here, we perform comprehensive density functional theory (DFT) and experimental investigations to discover the detailed catalytic efficacy of siloxane exchange and provide direction for the reaction process using a 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) catalyst. The calculated transition barrier energy and catalytic efficiency of hexamethyldisiloxane and dihydroxy-dimethylsilane exchange derived from the nudged elastic band with transition-state calculations strongly agree with the experimental findings. In addition, Fukui indices, along with partial charges, are employed to evaluate the nucleophilic and electrophilic behaviors of silanol and siloxane molecules. Our analysis revealed that by utilizing the Fukui indices of both the acid and the base, we can make an approximate estimation of the respective kinetics of the SN2 process in the siloxane exchange reaction mechanism. These findings establish a foundation for comprehending a crucial aspect of the exchange mechanism in siloxane vitrimer systems and could aid in the development of novel catalysts.

Enhanced synthesis of sponge-type multiwalled carbon nanotubes using SiO2-Fe2O3 catalysts via aerosol-assisted chemical vapor deposition: Electrochemical and absorption capacity studies

Carbon nanotube sponges synthesized at the laboratory scale typically use a Fe-based organometallic catalyst, but low-cost alternatives with a higher yield ratio are needed for large-scale production. This work introduces a catalyst made from a mixture of silicon dioxide (SiO2) and hematite (Fe2O3) as an innovative alternative for the high-yield production of spongy-type multi-walled carbon nanotubes (ST-MWCNTs). We used a ball-milled mixture of SiO2 and Fe2O3 powders as the catalyst and toluene and N, N-dimethylformamide as carbon and nitrogen sources in an aerosol-assisted catalytic chemical vapor deposition system. Incorporating SiO2 into the Fe-based catalyst increased production yield to 184 % of the catalyst weight. The synthesized ST-MWCNTs exhibited a high crystallinity ratio (ID/IG = 0.34) with a unique entangled bundle-type nanotube configuration. At the same time, the presence of Si atoms and oxygen-type functionalities, demonstrated by X-ray photoelectron spectroscopy, modified their electrochemical behavior, making them suitable for supercapacitor or sensor applications. Additionally, the spongy structure demonstrated a reversible absorption capacity of over 15 times its weight with organic solvents like gasoline or ethylene glycol. This new catalyst configuration opens alternatives for generating higher amounts of 3D carbon nanomaterials with potential energy storage, water filtration, and environmental remediation applications.

Monodentate Phosphinoamine Nickel Complex Supported on a Metal-Organic Framework for High-Performance Ethylene Dimerization.

Ethylene dimerization is an efficient industrial chemical process to produce 1-butene, with demanding selectivity and activity requirements on new catalytic systems. Herein, a series of monodentate phosphinoamine-nickel complexes immobilized on UiO-66 are described for ethylene dimerization. These catalysts display extensive molecular tunability of the ligand similar to organometallic catalysis, while maintaining the high stability attributed to the metal-organic framework (MOF)scaffold. The highly flexible postsynthetic modification method enables this study to prepare MOFs functionalized with five different substituted phosphines and 3 N-containing ligands and identify the optimal catalyst UiO-66-L5-NiCl2 with isopropyl substituted nickel mono-phosphinoamine complex. This catalyst shows a remarkable activity and selectivity with a TOF of 29000 (molethyl/molNi/h) and 99% selectivity for 1-butene under ethylene pressure of 15bar. The catalyst is also applicable for continuous production in the packed column micro-reactor with a TON of 72000 (molethyl/molNi). The mechanistic insight for the ethylene oligomerization has been examined by density functional theory (DFT) calculations. The calculated energy profiles for homogeneous complexes and truncated MOF models reveal varying rate-determining step as β-hydrogen elimination and migratory insertion, respectively. The activation barrier of UiO-66-L5-NiCl2 is lower than other systems, possibly due to the restriction effect caused by clusters and ligands. A comprehensive analysis of the structural parameters of catalysts shows that the cone angle as steric descriptor and butene desorption energy as thermodynamic descriptor can be applied to estimate the reactivity turnover frequency (TOF) with the optimum for UiO-66-L5-NiCl2. This work represents the systematic optimization of ligand effect through combination of experimental and theoretical data and presents a proof-of-concept for ethylene dimerization catalyst through simple heterogenization of organometallic catalyst on MOF.

Non-Oxidative Coupling of Methane Catalyzed by Heterogeneous Catalysts Containing Singly Dispersed Metal Sites

Direct upgrading of methane into value-added products is one of the most significant technologies for the effective transformation of hydrocarbon feedstocks in the chemical industry. Both oxidative and non-oxidative methane conversion are broadly useful approaches, though the two reaction pathways are quite distinguished. Oxidative coupling of methane (OCM) has been widely studied, but suffers from the low selectivity to C2 hydrocarbons because of the overoxidation leading to undesired byproducts. Therefore, non-oxidative coupling of methane is a worthy alternative approach to be developed for the efficient, direct utilization of methane. Recently, heterogeneous catalysts comprising singly dispersed metal sites, such as single-atom catalysts (SAC) and surface organometallic catalysts (SOMCat), have been proven to be effectively active for direct coupling of methane to product hydrogen and C2 products. In this context, this review summarizes recent discoveries of these novel catalysts and provides a perspective on promising catalytic processes for methane transformation via non-oxidative coupling.

Palladium anchored to BisPyP@bilayer-SiO2@NMP organic–inorganic hybrid as an efficient and recoverable novel nanocatalyst in suzuki and stille C–C coupling reactions

The palladium anchored to BisPyP@bilayer-SiO2@NMP organic–inorganic hybrid was employed as an effective and recyclable organometallic catalyst in Suzuki and Stille C–C coupling reactions. The structure of this magnetic nanocatalyst was determined using various techniques such as SEM, TEM, FT-IR, EDS, ICP-OES, VSM, N2 adsorption–desorption isotherms, XRD, and TGA. In both of the mentioned coupling paths, the yields of the products were very favorable and ranged from 90 to 98%. Also, they had significant features compared to previous reports, such as very short reaction time (5–15 and 7–20 min respectively in the Suzuki and Stille reactions), easy work-up, broad substrate scope, ease of separation of the catalyst using a magnet, suitable reproducibility of the catalyst in 6 runs, heterogeneous nature of the catalyst and not washing it during consecutive runs with confirmation of hot filtration and ICP-OES methods.

Regulating Access to Active Sites via Hydrogen Bonding and Cation-Dipole Interactions: A Dual Cofactor Approach to Switchable Catalysis.

Hydrogen bonding networks are ubiquitous in biological systems and play a key role in controlling the conformational dynamics and allosteric interactions of enzymes. Yet in small organometallic catalysts, hydrogen bonding rarely controls ligand binding to the metal center. In this work, a hydrogen bonding network within a well-defined organometallic catalyst works in concert with cation-dipole interactions to gate substrate access to the active site. An ammine ligand acts as one cofactor, templating a hydrogen bonding network within a pendent crown ether and preventing the binding of strong donor ligands, such as nitriles, to the nickel center. Sodium ions are the second cofactor, disrupting hydrogen bonding to enable switchable ligand substitution reactions. Thermodynamic analyses provide insight into the energetic requirements of the different supramolecular interactions that enable substrate gating. The dual cofactor approach enables switchable catalytic hydroamination of crotononitrile. Systematic comparisons of catalysts with varying structural features provide support for the critical role of the dual cofactors in achieving on/off catalysis with substrates containing strongly donating functional groups that might otherwise interfere with switchable catalysts.

Differentiating the Yield of Chemical Reactions Using Parameters in First-Order Kinetic Equations to Identify Elementary Steps That Control the Reactivity from Complicated Reaction Path Networks.

The yield of a chemical reaction is obtained by solving its rate equation. This study introduces an approach for differentiating yields by utilizing the parameters of the rate equation, which is expressed as a first-order linear differential equation. The yield derivative for a specific pair of reactants and products is derived by mathematically expressing the rate constant matrix contraction method, which is a simple kinetic analysis method. The parameters of the rate equation are the Gibbs energies of the intermediates and transition states in the reaction path network used to formulate the rate equation. Thus, our approach for differentiating the yield allows a numerical evaluation of the contribution of energy variation to the yield for each intermediate and transition state in the reaction path network. In other words, a comparison of these values automatically extracts the factors affecting the yield from a complicated reaction path network consisting of numerous reaction paths and intermediates. This study verifies the behavior of the proposed approach through numerical experiments on the reaction path networks of a model system and the Rh-catalyzed hydroformylation reaction. Moreover, the possibility of using this approach for designing ligands in organometallic catalysts is discussed.

Synthesis of N,N′-alkylidene bisamides and Suzuki–Miyaura coupling reaction derivatives with Pd organometallic catalyst anchored to channels of mesoporous silica MCM-41

At first, an organometallic catalyst namely, Pd-DPyE@MCM-41@MNP was prepared through magnetic (Fe3O4) nanoparticles-doped into channels of mesoporous silica MCM-41 and then, anchoring a novel complex composed of di(4-pyridyl)ethylene and palladium on the inner surface of the support. This immobilized catalyst was successfully identified via VSM, ICP-OES, TEM, FTIR, TGA, SEM, BET, XRD, EDX and elemental mapping analyses. After that, it was used as a versatile, heterogeneous, and magnetically reproducible catalyst in the generation of N,N′-alkylidene bisamides (1a-13a, 8–20 min, 90–98%, 50 °C, solvent-free) and Suzuki–Miyaura coupling (SMC) reaction derivatives (1b-26b, 10–140 min, 86–98%, 60 °C, PEG-400). The VSM plot of Pd-DPyE@MCM-41@MNP displays that this nanocatalyst can be easily recycled by applying an external magnetic field. In both synthetic paths, this nanocatalyst was reused at least seven times without palladium leaching and significantly reducing its catalytic performance. Also, stability and heterogeneous nature of catalyst were approved via ICP-OES technique and hot filtration test.

Self‐assembly aryl cyclopalladated imine film supported on the silicon surface—Fabrication, formation of active PdPd/PdO sites, and catalytic properties for Sonogashira cross‐coupling reaction

Tailoring the structure and arrangement of the organometallic catalyst are essential for the fundamental investigating and applications, and the impacting challenges, such as the size, active species distribution, and composition, as well as the orientation of catalyst, are critical for determining their activities and efficiencies. Herein, a series of aryl cyclopalladated catalysts containing different alkane chains were synthesized, and their self‐assembly films covalent binding to the silicon surface were fabricated and characterized with water drop contact angle, Raman, atomic force microscopy, scanning electron microscopy, and X‐ray photoelectron spectroscopy. The catalytic performances of these catalytic films were explored using Sonogashira cross‐coupling reaction as a template. One of these catalytic films exhibited a higher catalytic activity with a TON value of up to 68,333 h−1, which was 20 times higher than that of homogeneous catalyst due to the ordered arrangement of this catalyst on the silicon surface, and could be reused at least seven times. The catalytic mechanism was heterogeneous catalysis occurred at interface confirmed by hot filtration tests, poisoning tests, and ReactIR. The real active site was PdPd/PdO, and the synergistic effect between Pd and PdO in the active sites (PdPd/PdO) made the key initial oxidation step easily proceed, improving its catalytic activity. The loss of active sites and residues absorbed on the surface of catalytic film were the main reason for deactivation.

Novel organometallic catalyst for efficient valorization of lipids extracted from Prunus domestica kernel shell in sustainable fuel production

This study focuses on converting Plum Kernel Shell (PKS) waste biomass into biodiesel using a novel synthesized heterogeneous catalyst, contributing to the pursuit of renewable fuel from sustainable resources. Plum Kernel Shell (PKS) is waste biomass generated from plum fruit and available abundantly; utilizing it can help in many ways, such as overcoming environmental issues and promoting a circular economy. The precursor for the heterogeneous catalyst is derived from post-oil extraction waste biomass and further modified with metallic oxides (CuO and Mo) due to its acidic nature to enhance its efficacy for biodiesel production. Thorough characterization of the synthesized catalyst was conducted using analytical techniques such as XRD (X-ray diffraction), SEM (Scanning Electron Microscopy), EDS (Energy-Dispersive X-ray Spectroscopy), BET (Brunauer-Emmett-Teller), and XPS (X-ray Photoelectron Spectroscopy) to elucidate its nature and performance. The transesterification process was systematically optimized by varying parameters such as temperature, time, methanol-to-oil ratio, and catalyst loading. The optimized yield of 92.61 % of biodiesel resulted under ideal conditions, specifically at 65 °C, 150 min, 5 wt% catalyst loading, and an 18:1 M ratio. The biodiesel derived from PKS oil exhibited promising fuel properties encompassing cold flow properties, density, viscosity, cetane number, and flash point, validating its potential as a viable alternative fuel source. Furthermore, the synthesized novel catalyst demonstrated exceptional efficiency, retaining stability over five cycles without significant reduction in biodiesel yield. These findings underscore the viability of PKS biomass as a renewable and sustainable source for both catalyst synthesis and biodiesel production.

The Rhodium Analogue of Coenzyme B12 as an Anti‐Photoregulatory Ligand Inhibiting Bacterial CarH Photoreceptors

AbstractCoenzyme B12 (AdoCbl; 5′‐deoxy‐5′‐adenosylcobalamin), the quintessential biological organometallic radical catalyst, has a formerly unanticipated, yet extensive, role in photoregulation in bacteria. The light‐responsive cobalt‐corrin AdoCbl performs this nonenzymatic role by facilitating the assembly of CarH photoreceptors into DNA‐binding tetramers in the dark, suppressing gene expression. Conversely, exposure to light triggers the decomposition of this AdoCbl‐bound complex by a still elusive photochemical mechanism, activating gene expression. Here, we have examined AdoRhbl, the non‐natural rhodium analogue of AdoCbl, as a photostable isostructural surrogate for AdoCbl. We show that AdoRhbl closely emulates AdoCbl in its uptake by bacterial cells and structural functionality as a regulatory ligand for CarH tetramerization, DNA binding, and repressor activity. Remarkably, we find AdoRhbl is photostable even when bound “base‐off/His‐on” to CarH in vitro and in vivo. Thus, AdoRhbl, an antivitamin B12, also represents an unprecedented anti‐photoregulatory ligand, opening a pathway to precisely target biomimetic inhibition of AdoCbl‐based photoregulation, with new possibilities for selective antibacterial applications. Computational biomolecular analysis of AdoRhbl binding to CarH yields detailed structural insights into this complex, which suggest that the adenosyl group of photoexcited AdoCbl bound to CarH may specifically undergo a concerted non‐radical syn‐1,2‐elimination mechanism, an aspect not previously considered for this photoreceptor.

The Rhodium Analogue of Coenzyme B12 as an Anti-Photoregulatory Ligand Inhibiting Bacterial CarH Photoreceptors.

Coenzyme B12 (AdoCbl; 5'-deoxy-5'-adenosylcobalamin), the quintessential biological organometallic radical catalyst, has a formerly unanticipated, yet extensive, role in photoregulation in bacteria. The light-responsive cobalt-corrin AdoCbl performs this nonenzymatic role by facilitating the assembly of CarH photoreceptors into DNA-binding tetramers in the dark, suppressing gene expression. Conversely, exposure to light triggers the decomposition of this AdoCbl-bound complex by a still elusive photochemical mechanism, activating gene expression. Here, we have examined AdoRhbl, the non-natural rhodium analogue of AdoCbl, as a photostable isostructural surrogate for AdoCbl. We show that AdoRhbl closely emulates AdoCbl in its uptake by bacterial cells and structural functionality as a regulatory ligand for CarH tetramerization, DNA binding, and repressor activity. Remarkably, we find AdoRhbl is photostable even when bound "base-off/His-on" to CarH in vitro and in vivo. Thus, AdoRhbl, an antivitamin B12, also represents an unprecedented anti-photoregulatory ligand, opening a pathway to precisely target biomimetic inhibition of AdoCbl-based photoregulation, with new possibilities for selective antibacterial applications. Computational biomolecular analysis of AdoRhbl binding to CarH yields detailed structural insights into this complex, which suggest that the adenosyl group of photoexcited AdoCbl bound to CarH may specifically undergo a concerted non-radical syn-1,2-elimination mechanism, an aspect not previously considered for this photoreceptor.

Access to Saturated Aza‐Heterocycles using the Borrowing Hydrogen Methodology

AbstractBorrowing hydrogen (BH) has reached a wide attention from the chemistry community as a new opportunity to construct efficiently C−N bond (as well as C−C or C−S bond). This straightforward strategy is usually supported by relevant organometallic catalysts, involved in the dehydrogenation‐reduction processes. This concept highlights specifically the application of the borrowing hydrogen to the preparation of saturated aza‐heterocycles (piperidines, pyrrolidines and piperazines) extensively present in high‐added value molecules of pharmaceutical industry over the last 40 years using homogenous catalysis in particular. A focus will be given to the appropriate metals (Ru, Ir and more recently earth‐abundant metals) used for this transformation. An extension to chiral induction in order to prepare enantiopure N‐heterocycles will be also reported.

Stereoselective Ring-opening Polymerization of S-Carboxyanhydrides Using Salen Aluminum Catalysts: A Route to High-Isotactic Functionalized Polythioesters.

Polythioesters are important sustainable polymers with broad applications. The ring-opening polymerization (ROP) of S-Carboxyanhydrides (SCAs) can afford polythioesters with functional groups that are typically difficult to prepare by ROP of thiolactones. Typical methods involving organocatalysts, like dimethylaminopyridine (DMAP) and triethylamine (Et3 N), have been plagued by uncontrolled polymerization, including epimerization for most SCAs resulting in the loss of isotacticity. Here, we report the use of salen aluminum catalysts for the selective ROP of various SCAs without epimerization, affording functionalized polythioester with high molecular weight up to 37.6 kDa and the highest Pm value up to 0.99. Notably, the ROP of TlaSCA (SCA prepared from thiolactic acid) generates the first example of a isotactic crystalline poly(thiolactic acid), which exhibited a distinct Tm value of 152.6 °C. Effective ligand tailoring governs the binding affinity between the sulfide chain-end and the metal center, thereby maintaining the activity of organometallic catalysts and reducing the occurrence of epimerization reactions.

Stereoselective Ring‐opening Polymerization of S‐Carboxyanhydrides Using Salen Aluminum Catalysts: A Route to High‐Isotactic Functionalized Polythioesters

AbstractPolythioesters are important sustainable polymers with broad applications. The ring‐opening polymerization (ROP) of S‐Carboxyanhydrides (SCAs) can afford polythioesters with functional groups that are typically difficult to prepare by ROP of thiolactones. Typical methods involving organocatalysts, like dimethylaminopyridine (DMAP) and triethylamine (Et3N), have been plagued by uncontrolled polymerization, including epimerization for most SCAs resulting in the loss of isotacticity. Here, we report the use of salen aluminum catalysts for the selective ROP of various SCAs without epimerization, affording functionalized polythioester with high molecular weight up to 37.6 kDa and the highest Pm value up to 0.99. Notably, the ROP of TlaSCA (SCA prepared from thiolactic acid) generates the first example of a isotactic crystalline poly(thiolactic acid), which exhibited a distinct Tm value of 152.6 °C. Effective ligand tailoring governs the binding affinity between the sulfide chain‐end and the metal center, thereby maintaining the activity of organometallic catalysts and reducing the occurrence of epimerization reactions.

Simmer-assisted in situ synthesis of an amorphous organometallic complex-doped NiFe catalyst with nanoflower architecture for efficient electrochemical overall water splitting

Developing efficient non-precious-metal-based bifunctional electrocatalysts for overall water splitting (OWS) is of great significance from both industrial and environmental perspectives. Herein, a novel flower-like architectured nanocomposite containing amorphous NiFe-hydroxide and NiFe-thiourea coordination complex, namely NiFe(OxHy)(TU)/NF, has been in situ synthesized on nickel foam by a simple simmer-assisted synthesis method. This nanomaterial demonstrates remarkable electrocatalytic performance and long-lasting durability for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Specifically, the overpotentials required to achieve a current density of 50 mA cm−2 for HER and OER are as low as 273 and 243 mV, respectively. Moreover, the OWS electrolyzer assembled using NiFe(OxHy)(TU)/NF as both anodic and cathodic electrodes operates efficiently with an exceptionally low cell voltage of 1.47 V and 1.72 V at a current density of 10 mA cm−2 and 50 mA cm−2, exhibiting negligible fluctuation over 55 hours. And this device can also be facilely driven by the photovoltaic cell. These excellent catalytic performances of NiFe(OxHy)(TU)/NF can be attributed to the electronic synergistic effects among multiple NiFe species like NiFe-hydroxide and NiFe-thiourea, as well as the abundant active sites induced by the nanoflower-like amorphous hierarchical structure. This study presents a practical and facile strategy for the synthesis of NiFe-based amorphous nanomaterial with robust OER and HER performances, thereby contributing to the advancement of multi-component bifunctional electrocatalysts.