Co9S8-CuS-FeS trimetal sulfides for excellent oxygen evolution reaction electrocatalysis

Self-Supported NiCo2S4@Ce-NiFe LDH/CeO2 Nanoarrays for Electrochemical Water Splitting

The design of high-performance OER catalysts is crucial for efficient electrochemical water splitting (EWS). Herein, a NiCo2S4@Ce-NiFe LDH/CeO2 heterostructure nanoarray electrocatalyst with abundant oxygen defect sites is reported. The introduction of Ce species activates the lattice oxygen in the oxyhydroxides, inducing the transformation of the catalytic mechanism toward the lattice oxygen oxidation mechanism (LOM) pathway, bypassing the thermodynamic limitation of the adsorbate evolution mechanism (AEM), and strengthening the intrinsic activity of the material. Moreover, the reversible transitions between different oxidation states of Ce species and the high oxygen storage capacity of CeO2 regulate the adsorption behavior of the reaction intermediates, allowing it to be easier for the material to enrich the oxygen-containing intermediates, thereby improving the adsorption kinetics. Accordingly, NiCo2S4@Ce-NiFe LDH/CeO2 exhibits remarkable OER performance (η50 = 226 mV, η100 = 244 mV) and brilliant stability. Additionally, the presence of the CeO2 protective layer inhibits the impact of Cl- and other pollutants in seawater, which enables NiCo2S4@Ce-NiFe LDH/CeO2 to perform satisfactorily in seawater electrolysis, as well. This study offers a fresh perspective on the design of defect-rich OER catalysts.

Enhanced removal of tetrabromobisphenolA (TBBPA) from e-waste by Fe-S nanoparticles and Fe-S/CuS nanocomposite with response surface methodology (RSM)

TetrabromobisphenolA is a well-known member of the brominated flame retardant group and is widely used as a highly effective fire-retardant additive in electronic and electrical equipment. TBBPA is commonly found in various environmental sources and can be harmful to human health. This study presents a simple approach to preparing a magnetic nanocomposite, offering a straightforward method that results in consistent quality and low resource consumption. The nanocomposite has a high surface-to-volume ratio for the removal of tetrabromobisphenolA. Various characterization techniques, including XRD, FTIR, EDX, FESEM, VSM, TEM, and BET analyses were used to characterize the Fe-S nanoparticles and Fe-S/CuS. The results showed that Fe-S/CuS nanocomposite successfully removed over 97% of the initial TBBPA (15 mg L-1) under optimized conditions determined by RSM, such as a contact time of 15 min, pH of 7, Fe-S/CuS nanocomposite dosage of 0.69 g L-1, and salt concentration of 0.10%. The RSM analysis provided a second-order polynomial model with a confidence level of 93% (F = 29.58; p < 0.0001) to predict the TBBPA removal efficiency at various concentrations. In the adsorption kinetic studies, the second-order kinetic model provided the best fit for the experimental data. Additionally, Fe-S/CuS nanocomposite shows great potential for practical applications and environmental remediation efforts, making it a valuable asset for real-sample use in environmental settings.

Powering the Future by Iron Sulfide Type Material (FexSy) Based Electrochemical Materials for Water Splitting and Energy Storage Applications: A Review

Water electrolysis is among the recent alternatives for generating clean fuels (hydrogen). It is an efficient way to produce pure hydrogen at a rapid pace with no unwanted by-products. Effective and cheap water-splitting electrocatalysts with enhanced activity, specificity, and stability are currently widely studied. In this regard, noble metal-free transition metal-based catalysts are of high interest. Iron sulfide (FeS) is one of the essential electrocatalysts for water splitting because of its unique structural and electrochemical features. This article discusses the significance of FeS and its nanocomposites as efficient electrocatalysts for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), oxygen reduction reaction (ORR), and overall water splitting. FeS and its nanocomposites have been studied also for energy storage in the form of electrode materials in supercapacitors and lithium- (LIBs) and sodium-ion batteries (SIBs). The structural and electrochemical characteristics of FeS and its nanocomposites, as well as the synthesis processes, are discussed in this work. This discussion correlates these features with the requirements for electrocatalysts in overall water splitting and its associated reactions. As a result, this study provides a road map for researchers seeking economically viable, environmentally friendly, and efficient electrochemical materials in the fields of green energy production and storage.

Two Electrocatalytic Selenoarsenates with Manganese Complex Cations as Counterions

The discovery of new organic hybrid chalcogenidometalates is of great importance for structural chemistry and functional material. Here, new types of organic hybrid selenoarsenates [Mn(dien)2]2[AsII4Se6] (1, dien = diethylenetriamine) and [Mn(dien)2]2[Mn(AsIIISe3)2] (2) have been solvothermally synthesized by the reaction of K3AsO3, Se, and MnCl2·xH2O (x = 0, 2) in dien solution at 120 °C. 1 presents a hitherto unknown [AsII4Se6]4- anion with low-valent As2+ ion, which comprises a centrosymmetric six-membered [AsII4Se2] ring in chair-like conformation, while 2 contains a new type of heterometallic selenoarsenate(III) [Mn(AsIIISe3)2]4- constructed by the connection of one tetrahedral [MnSe4] and two rare noncondensed [AsIIISe3]3- anions. 1 and 2 were first combined with nickel nanoparticle (Ni) and the nickel foam (NF) for fabricating the 1/Ni/NF and 2/Ni/NF electrodes, which exhibited excellent oxygen evolution reaction electrocatalytic property with a low overpotential of 248 mV for 1 and 219 mV for 2 at 10 mA cm-2 in alkaline media.

Synergistic CuCoS-PANI materials for binder-free electrodes in asymmetric supercapacitors and oxygen evolution

In advanced electronics, supercapacitors (SCs) have received a lot of attention. Nevertheless, it has been shown that different electrode designs that are based on metal sulfides are prone to oxidation, instability, and poor conductance, which severely limits their practical application. We present a very stable, free-standing copper-cobalt sulfide doped with polyaniline as an electrode coated on nickel foam (CuCoS/PANI). The lightweight nickel foam encourages current collection as well as serving as a flexible support. The CuCoS-PANI electrode had a substantially greater 1659 C g-1 capacity at 1.0 A g-1. The asymmetric supercapacitor (ASC) can provide an impressive 54 W h kg-1 energy density while maintaining 1150 W kg-1 power. Additionally, when employed as an electrocatalyst in the oxygen evolution reaction, CuCoS/PANI exhibited a 200 mV overpotential and 55 mV dec-1 Tafel slope, demonstrating its effectiveness in facilitating the reaction.

A Review of Transition Metal Boride, Carbide, Pnictide, and Chalcogenide Water Oxidation Electrocatalysts

Transition metal borides, carbides, pnictides, and chalcogenides (X-ides) have emerged as a class of materials for the oxygen evolution reaction (OER). Because of their high earth abundance, electrical conductivity, and OER performance, these electrocatalysts have the potential to enable the practical application of green energy conversion and storage. Under OER potentials, X-ide electrocatalysts demonstrate various degrees of oxidation resistance due to their differences in chemical composition, crystal structure, and morphology. Depending on their resistance to oxidation, these catalysts will fall into one of three post-OER electrocatalyst categories: fully oxidized oxide/(oxy)hydroxide material, partially oxidized core@shell structure, and unoxidized material. In the past ten years (from 2013 to 2022), over 890 peer-reviewed research papers have focused on X-ide OER electrocatalysts. Previous review papers have provided limited conclusions and have omitted the significance of "catalytically active sites/species/phases" in X-ide OER electrocatalysts. In this review, a comprehensive summary of (i) experimental parameters (e.g., substrates, electrocatalyst loading amounts, geometric overpotentials, Tafel slopes, etc.) and (ii) electrochemical stability tests and post-analyses in X-ide OER electrocatalyst publications from 2013 to 2022 is provided. Both mono and polyanion X-ides are discussed and classified with respect to their material transformation during the OER. Special analytical techniques employed to study X-ide reconstruction are also evaluated. Additionally, future challenges and questions yet to be answered are provided in each section. This review aims to provide researchers with a toolkit to approach X-ide OER electrocatalyst research and to showcase necessary avenues for future investigation.

Skeleton-coated CoCu-Based bimetal hollow nanoprisms as High-Performance electrocatalysts for oxygen evolution reaction

CoSx materials with high catalytic activity are considered as promising HER electrocatalysts, but their inherent low electrical conductivity and easy loss of active sites have greatly limited their applications in OER electrocatalysis. Herein, we present a convenient method to synthesize Co-Cu hollow nanoprisms after wrapping and calcining with trithiocyanuric acid (C3H3N3S3) (denoted N-Co-Cu-S-x HNs). The results showed that Cu doping modified the charge density of Co center, leading to the enhancement of the intrinsic activity of the Co3S4 active center, meanwhile wrapping trithiocyanuric acid on the surfaces and calcinating to form N-containing C skeleton as a flexible substrate to encapsulate the catalysts, which effectively protected the active sites inside the catalysts. Notably, the OER catalyst that was optimized by adjusting the metal ratio and controlling the trithiocyanuric acid incorporation exhibited a low overpotential of 306 mV under a current density of 10 mA cm-2 and showed a superior durability of more than 27 h. This work may provide some insights into the preparation of oxygen evolution reaction catalysts with excellent performance through doping transition metals and protecting the internal active sites strategies.

In situ generated Cu-Co-Zn trimetallic sulfide nanoflowers on copper foam: a highly efficient OER electrocatalyst

The electrocatalytic oxygen evolution reaction (OER) is an integral part and a stepping stone to various electrochemical technologies in the field of electrochemical energy conversion. The development of OER catalysts with low-cost materials, industry-related activity and long-term durability is highly needed, but remains challenging at this stage. In this paper, Cu ions in a copper foam (CF) substrate were replaced with Cu(OH)₂ grown on CF to participate in the subsequent reaction, and then a subsequent two-step hydrothermal method was used to obtain the nanoflower-like Cu-Co-Zn trimetallic sulfide (named CuCoZn-S-3) catalyst, whose unique flower structure ensures that the catalyst surface exhibits a larger electrochemical active area, so as to expose plentiful active sites. The synergism between metals regulates the electron environment and accelerates the charge transfer rate, greatly improving the electrocatalytic activity of the catalyst. The prepared CuCoZn-S-3 exhibits excellent OER performance under alkaline conditions. It requires overpotentials of only 175 mV and 242 mV to drive current densities of 10 mA cm^-2 and 100 mA cm^-2, respectively. The Tafel slope of CuCoZn-S-3 is 62.3 mV dec^-1. This study may provide a viable strategy for the rational preparation of low-cost and efficient OER electrocatalysts in alkaline medium.

Electrochemical tuning of a Cu3P/Ni2P hybrid for a promoted hydrogen evolution reaction

Developing novel and high performance electrocatalysts for use in hydrogen evolution reactions (HER) as substitutes for noble metal based electrocatalysts is imperative and, so far, has been a challenge. Herein, a self-supported Cu₃P/Ni₂P hybrid on nickel foam (Cu₃P/Ni₂P@NF) is prepared by a simple galvanic replacement reaction coupled with phosphorization. Subsequently, Cu₃P/Ni₂P@NF is modified by conducting cyclic voltammetry scans in 0.5 M H₂SO₄ solution. Interestingly, after electrochemical tuning, the as-prepared Cu₃P/Ni₂P@NF exhibits significantly enhanced HER activity. Particularly, the resultant Cu₃P/Ni₂P@NF catalyst after 4000 cycles exhibits superior catalytic activity and long-term stability for HER with an overpotential of only 67 mV at the current density of 10 mA cm^-2, and a low Tafel slope of 43.9 mV dec^-1. The improved HER performance is attributed to the increased intrinsic activity of the Cu₃P/Ni₂P@NF with its optimized crystal and electronic structure, as well as an increased number of accessible active sites due to surface dissolution and recrystallization induced by electrochemical modification.

Bimetallic copper nickel sulfide electrocatalyst by one step chemical bath deposition for efficient and stable overall water splitting applications

Transition metal sulfides have been intensively investigated as an effective catalyst for overall water splitting application due to their inexorable bifunctional oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activity. However, the chalcogenides are oxidised during the OER process and hence limit the stability of the electrocatalyst. The synthesized materials should have a higher oxidation state corresponding to the active species in order to improve the stability. In this study, we have employed a one-step chemical bath deposition (CBD) route to synthesis bimetallic copper nickel sulfide (CuNiS) electrocatalyst. We have accomplished a superior OER electrocatalytic activity with a lower overpotential of 337 mV at 10 mA/cm² current density and a small Tafel slope of 43 mV/dec. Also, we have achieved an excellent HER activity with a very low overpotential of 99 mV at 10 mA/cm² and a Tafel slope of 63 mV/dec. The constructed electrolyzer attained a lower cell voltage of only 1.55 V to reach the current density of 10 mA/cm²_. The stability test carried at a high current density of 200 mA/cm² for 50 h showed less than 5% increase in Ni³⁺ active species at the surface ensure the stable performance nature. Thus, this work provides a promising methodology for the synthesis of bimetallic sulfides for enhanced electrocatalytic water splitting with exceptional reliability.

Constructing ultrathin FeS/FeOxH@Fe nano-sheets for highly efficient oxygen evolution reaction

Exploring earth-abundant catalysts with ultra-high activity and durability are the decisive challenges for oxygen evolution reaction. This work prepared the FeS/FeO_xH@Fe nanosheets as the efficient and stable electrocatalysts of oxygen evolution reaction (OER) through a simple one-step co-deposition method. The FeS/FeO_xH@Fe exhibited small overpotentials of 245, 376 and 482 mV at the current density of 10, 500 and 1000 mA cm^-2 without iR-compensations in 1.0 M KOH solution, respectively. Constructing amorphous structure and the interface between amorphous and crystal can obviously improve the conductivity of FeO_xH, which is beneficial to the improvement of catalytic performance. This work may provide an effective and controlled strategy to design highly active OER catalysts with an interface structure between amorphous and crystal by a well-designed co-deposition.

Novel WS2 /Fe0.95 S1.05 Hierarchical Nanosphere as a Highly Efficient Electrocatalyst for Hydrogen Evolution Reaction

Fe_0.95 S_1.05 with high reactivity and stability was incorporated into WS₂ nanosheets via a one-step solvothermal method for the first time. The resulted hybrid catalyst has much higher catalytic activity than WS₂ and Fe_0.95 S_1.05 alone, and the optimal WS₂ /Fe_0.95 S_1.05 hybrid catalyst was found by adjusting the feed ratio. The addition of Fe_0.95 S_1.05 was proven to be able to enhance the hydrogen evolution reaction (HER) activity of WS₂ , and vice versa. At the same time, it was found that the catalytic effect of the hybrid catalyst was the best when the feed ratio was W : Fe=2 : 1. In other words, we confirmed that there is a synergistic effect between W- and Fe-based sulfide hybrid catalysts, and validated that the reason for the improved HER performance is the strong interaction between the two in the middle sulfur. WS₂ /Fe_0.95 S_1.05 -2 hybrid catalyst leads to enhanced HER activity, which shows a low overpotential of ∼0.172 V at 10 mA cm^-2 , low Tafel slope of ∼53.47 mV/decade. This study supplies innovative synthesis of a highly active WS₂ /Fe_0.95 S_1.05 hybrid catalyst for HER.

FeCoNi Sulfides Derived From In situ Sulfurization of Precursor Oxides as Oxygen Evolution Reaction Catalyst

It is highly promising to design and develop efficient and economical electrocatalysts for oxygen evolution reaction (OER) in alkaline solution. In this work, we prepare FeCoNi sulfide composites (including FeS, Co₃S₄, and Ni₃S₄) derived from in situ sulfurization of precursor oxides on carbon cloth (CC), which are used to become an OER catalyst. Such catalyst shows excellent OER performance, low overpotential, small Tafel slope, and high electrochemical stability, and it is a promising electrocatalyst for OER in alkaline media.

A Low-Temperature Molecular Precursor Approach to Copper-Based Nano-Sized Digenite Mineral for Efficient Electrocatalytic Oxygen Evolution Reaction

In the urge of designing noble metal-free and sustainable electrocatalysts for oxygen evolution reaction (OER), herein, a mineral Digenite Cu9 S5 has been prepared from a molecular copper(I) precursor, [{(PyHS)2 CuI (PyHS)}2 ](OTf)2 (1), and utilized as an anode material in electrocatalytic OER for the first time. A hot injection of 1 yielded a pure phase and highly crystalline Cu9 S5 , which was then electrophoretically deposited (EPD) on a highly conducting nickel foam (NF) substrate. When assessed as an electrode for OER, the Cu9 S5 /NF displayed an overpotential of merely 298±3 mV at a current density of 10 mA cm-2 in alkaline media. The overpotential recorded here supersedes the value obtained for the best reported Cu-based as well as the benchmark precious-metal-based RuO2 and IrO2 electrocatalysts. In addition, the choronoamperometric OER indicated the superior stability of Cu9 S5 /NF, rendering its suitability as the sustainable anode material for practical feasibility. The excellent catalytic activity of Cu9 S5 can be attributed to the formation of a crystalline CuO overlayer on the conductive Cu9 S5 that behaves as active species to facilitate OER. This study delivers a distinct molecular precursor approach to produce highly active copper-based catalysts that could be used as an efficient and durable OER electro(pre)catalysts relying on non-precious metals.

Synthesis of one dimensional Cu2S nanorods using a self-grown sacrificial template for the electrocatalytic oxygen evolution reaction (OER)

The oxygen evolution reaction (OER) is critical in electrochemical water splitting and requires an efficient, sustainable, and cheap catalyst for successful practical applications.

In situ fabrication of dynamic self-optimizing Ni3S2 nanosheets as an efficient catalyst for the oxygen evolution reaction

Ni₃S₂ nanosheets exhibit enhanced oxygen evolution reaction performance by self-optimizing their surface composition.

A novel FeS–NiS hybrid nanoarray: an efficient and durable electrocatalyst for alkaline water oxidation

A novel FeS–NiS/TM nanosheet array was developed for alkaline OER; this catalyst only requires an overpotential of 260 mV to afford a current density of 10 mA cm⁻² in 1.0 M KOH.