Catalysts For Overall Water Splitting Research Articles

Iron, Tungsten Dual-Doped Nickel Sulfide as Efficient Bifunctional Catalyst for Overall Water Splitting.

Developing low-cost and highly efficient bifunctional catalysts for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) is a challenging problem in electrochemical overall water splitting. Here, iron, tungsten dual-doped nickel sulfide catalyst (Fe/W-Ni3S2) is synthesized on the nickel foam, and it exhibits excellent OER and HER performance. As a result, the water electrolyze based on Fe/W-Ni3S2 bifunctional catalyst illustrates 10mAcm-2 at 1.69V (without iR-compensation) and highly durable overall water splitting over 100h tested under 500mAcm-2. Experimental results and DFT calculations indicate that the synergistic interaction between Fe doping and Ni vacancy induced by W leaching during the in situ oxidation process can maximize exposed OER active sites on the reconstructed NiOOH species for accelerating OER kinetics, while the Fe/W dual-doping optimizes the electronic structure of Fe/W-Ni3S2 and the binding strength of intermediates for boosting HER. This study unlocks the different promoting mechanisms of incorporating Fe and W for boosting the OER and HER activity of Ni3S2 for water splitting, which provides significant guidance for designing high-performance bifunctional catalysts for overall water splitting.

Self-assembly of NiFe-LDH@Ni3S2 sub-nanosheets catalyst for overall water splitting

The development of water splitting catalysts for generating high-purity hydrogen in large-scale is still facing challenges in terms of improving efficiency and stability. Herein, Ni3S2-coated NiFe layered double hydroxides sub-nanosheets with a hierarchical heterostructure (NiFe-LDH@Ni3S2) were prepared on nickel foam (NF) by a strategy of continuous hydrothermal synthesis. The introduction of S2− broke the hydrogen bonds between NiFe-LDH layers and separated into sub-nanosheets with a thickness of only about 1 nm, which enlarged the active areas of NiFe-LDH@Ni3S2/NF by a factor of 5.7. The coexisting charge channels Ni-O-Ni and Ni-S-Ni in the material enhanced the electrochemical activity, resulting in the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) overpotentials as low as 179 mV and 116 mV at 10 mA cm−2 in 1.0 M KOH. Moreover, after a 50-hour chronopotentiometry test at 50 mA cm−2, the overpotential for OER and HER decreased only 0.013 V and 0.059 V, respectively. Furthermore, under the conditions of simulating industrial hydrogen production with an electrolyte of 6.0 M KOH and a temperature of 75 °C, after a 140-hour test for durability, the current density decreased only 0.75% at the cell voltage of 1.70 V.

Oxygen-Deficient FeNbO4-x In-Situ Growth in Honey-Derived N-Doping Porous Carbon for Overall Water Splitting.

It is still a great challenge to reasonably design green, low cost, high activity and good stability catalysts for overall water splitting (OWS). Here, we introduce a novel catalyst with ferric niobate (FeNbO4) in-situ growing in honey-derived porous carbon of high specific surface area, and its catalytic activity is further enhanced by micro-regulation (oxygen vacancy and N-doping). From the experimental results and density functional theory (DFT) calculations, the oxygen vacancy in catalyst FeNbO4-x@NC regulates the local charge density of active site, thus increasing conductivity and optimizing hydrogen/oxygen species adsorption energy. FeNbO4 in-situ grows within N-doping honey-derived porous carbon, which can enhance active specific surface area exposure, strengthen gaseous substances escape rate, and accelerate electrons/ions transfer and electrolytes diffusion. Moreover, in-situ Raman also confirms O-species generation in oxygen evolution reaction (OER). As a result, the catalyst FeNbO4-x@NC shows good electrochemical performance in OER, HER and OWS.

In situ growth of highly wrinkled 3D volcano-like Fe3S4/Ni3S2/WO3/NiFe LDH/NF electrocatalyst for overall water splitting

The rational design of efficient, cost-effective, and durable electrocatalysts is crucial for the realization of hydrogen production through water splitting. The present study describes the synthesis of a novel three-dimensional (3D) volcano-like Fe3S4/Ni3S2/WO3/NiFe LDH/NF (Layered Double Hydroxides/Nickel Foam) electrocatalyst with a highly wrinkled structure through a two-step hydrothermal method. The as-synthesized electrocatalyst exhibits an exceptionally low overpotential of 77 mV for the hydrogen evolution reaction (HER) and 131 mV for the oxygen evolution reaction (OER) at a current density of 10 mA cm−2, owing to the unique morphology and strong electronic interactions between Fe3S4, Ni3S2 and WO3 heterostructures. The Fe3S4/Ni3S2/WO3/NiFe LDH/NF electrocatalyst demonstrates exceptional performance in overall water splitting when employed as both anode and cathode, achieving a current density of 10 mA cm−2 at an impressively low cell voltage of 1.5 V as well as exhibiting remarkable durability with little degradation over a period of 12 hours. This study presents a straightforward approach for the synthesis of highly efficient and durable non-noble metal catalysts for overall water splitting under hydrothermal conditions.

Coupling NiFe-MOF with antiperovskite nickel-based nitrides as efficient electrocatalysts for overall water splitting

The exploration of high-performance, durable and cost-effective catalysts for overall water splitting, including the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), has always been a vibrant topic in electrochemical water splitting techniques. Here we report a facile strategy for the synthesis of antiperovskite bimetallic nitrides (FeNNi3 and CuNNi3) and their NiFe-MOF morphology on nickel foams (NF) for HER and OER respectively in alkaline media. The NiFe-MOF and FeNNi3 nanoparticle exhibit strong coupling and synergistic effects, resulting in a solid integrated structure and fast electron transfer. The FeNNi3 towards HER shows an overpotential of 57 mV at 10 mA cm−2 in alkaline media, and its MOF morphology shows a low overpotential of 219 mV at 10 mA cm−2 towards OER. The alkaline electrolyzer of FeNNi3/NF || NiFe-MOF@FeNNi3/NF for overall water splitting demonstrates a low cell voltage of 1.49 V at 10 mA cm−2 with high cycling durability. This work investigates antiperovskite nitrides' capabilities for overall water splitting and provides guidance on designing high-performance catalytic materials.

Reversible surface reconstruction of bifunctional NiCu/FeNi2S4 heterostructure catalyst for overall water splitting

The synergistic effects of bifunctional catalysts in both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) must be better understood. Herein, the 3D hierarchical heterostructure consisting of NiCu surface layer assembled on the FeNi2S4 (or Ni-Fe layered-double-hydroxide, NiFe-LDH) is constructed on the nickel foam (NF) and the bifunctional catalytic effects of HER/OER are investigated in an alkaline solution. Although the high OER activity of NiFe-LDH and HER activity of NiCu/NF, NiCu/FeNi2S4 heterostructures is demonstrated by the small overpotentials of HER/OER (306 mV at a current density of 10 mA cm-2), in comparison with NiCu/NF (315 mV) and NiCu/NiFe-LDH (357 mV). An ultra-low cell voltage of 1.54 V is accomplished in overall water splitting. The high-performance bifunctional catalytic effects can be attributed to the synergistic effects of reversible surface reconstruction in the presence of S element, enabling the formation of the NiO/Ni interface at the low potential for HER and high oxidation states (Ni2+δ) at the high potential for OER. The results provide insights into the design of bifunctional electrocatalysts with high activity.

Special atmosphere annealed Co3O4 bifunctional catalysts with oxygen defects for high-efficient water splitting

Electrochemical water splitting is widely recognized as an economical and sustainable method for producing high-purity hydrogen using renewable energy sources. Herein, we prepared 3D urchin-like sphere structures of Co3O4 to serve as an excellent bifunctional catalyst for overall water splitting. Different Co3O4 samples were directly synthesized on Ni foam through hydrothermal and annealing processes under various atmospheric conditions, leading to the formation of oxygen vacancies with varying concentrations. Specifically, the Co3O4/NF-Ar/O2 demonstrates outstanding catalytic performance for both OER (η20 = 269 mV) and HER (η10 = 135 mV), while maintaining excellent durability in 1 M KOH. Electrolysis cells employing Co3O4/NF-Ar/O2 as both anode and cathode demonstrate a low cell voltage of 1.56 V to achieve 10 mV cm−2 in alkaline conditions. The excellent catalytic performance can be mainly attributed to the urchin-like nanostructure and the appropriate concentration of oxygen vacancies. This research provides further insights into the application of the method to induce oxygen vacancies in low-cost and high-efficiency transition metal oxides (TMOs)-based catalysts for electrochemical reaction.

An ultrathin flocculent Co9S8/Ni3S2 hybrid as high-performance bifunctional catalyst for overall water splitting

Modern industrial hydrogen production is a crucial solution to address the energy crisis. Therefore, the development of a cost-effective and highly efficient hydrolytic hydrogen production catalyst holds significant practical importance. In this study, we propose to synthesize an efficient bifunctional electrocatalyst of Co9S8/Ni3S2 grown on nickel foam (NF) by a one-step hydrothermal method, which has a large specific surface area due to its flocculated structure. Through electrochemical testing, the Co9S8/Ni3S2/NF electrode exhibits remarkable performance in both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Specifically, low overpotentials of 53.6, 90.2, and 209.2 mV are required to achieve current densities of 10, 20, and 100 mA/cm2 during HER, respectively. Similarly, for OER, the overpotentials are only 107.6, 150.6, and 350.4 mV. Additionally, the Co9S8/Ni3S2/NF electrode demonstrates a small Tafel slope of 68.7 mV/dec for HER and 91.8 mV/dec for OER, indicating efficient reaction kinetics. Notably, the electrode exhibits exceptional long-term stability. Moreover, in a self-assembled monolithic water splitting device with Co9S8/Ni3S2/NF electrodes as cathode and anode, a cell potential of 1.55 V is required to drive the overall water splitting process at a current density of 10 mA/cm2, and the reaction shows excellent stability with a loss of voltage of only 16.5 mV over a 10-hour period. This paper presents a simple and innovative approach for constructing bimetallic sulfides electrocatalysts.

Interfacial Electronic Modulation of Mo5N6/Ni3S2 Heterojunction Array Boosts Electrocatalytic Alkaline Overall Water Splitting

AbstractBifunctional electrocatalysts with excellent activity and durability are highly desirable for alkaline overall water splitting, yet remain a significant challenge. In this contribution, palm‐like Mo5N6/Ni3S2 heterojunction arrays anchored in conductive Ni foam (denoted as Mo5N6‐Ni3S2 HNPs/NF) are developed. Benefiting from the optimized electronic structure configuration, hierarchical branched structure and abundant heterogeneous interfaces, the as‐synthesized Mo5N6‐Ni3S2 HNPs/NF electrode exhibits remarkably stable bifunctional electrocatalytic activity in 1 m KOH solution. It only requires ultralow overpotentials of 59 and 190 mV to deliver a current density of 10 mA cm−2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1 m KOH solution, respectively. Importantly, the overall water splitting electrolyzer assembled by Mo5N6‐Ni3S2 HNPs/NF exhibits an exceptionally low cell voltage (1.48 V@10 mA cm−2) and outstanding durability, surpassing most of the reported Ni‐based bifunctional materials. Density functional theory (DFT) further confirms the heterostructure can optimize the Gibbs free energies of H and O‐containing intermediates (OH, O, OOH) during HER and OER processes, thereby accelerating the catalytic kinetics of electrochemical water splitting. The findings provide a new design strategy toward low‐cost and excellent catalysts for overall water splitting.

Ultrafast nanomanufacturing via high-temperature shock of La0.6Sr0.4CoO3 catalysts for overall water splitting

Electrochemical water splitting, as an effective sustainable and eco-friendly energy conversion strategy, can produce high-purity hydrogen (H2) and oxygen (O2) via hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, altering the nonrenewable fossil fuels. Here, La0.6Sr0.4CoO3 perovskite oxide nanoparticles with an orthorhombic phase were synthesized within 2 min in a one-step reaction, using a rapid and efficient high-temperature shock (HTS) method. Impressively, the as-prepared La0.6Sr0.4CoO3 with orthorhombic phase (HTS-2) exhibited better OER and HER performance than the hexagonal phase counterpart prepared using the traditional muffle furnace calcination method. The electrocatalytic performance enhancement of orthorhombic La0.6Sr0.4CoO3 can be attributed to the novel orthorhombic structure, such as confined strontium segregation, a higher percentage of highly oxidative oxygen species, and more active sites on the surface. This facile and rapid synthesis technique shows great potential for the rational design and crystal phase engineering of nanocatalysts.

Tuneable and coral-like NiCoP for enhanced oxygen and hydrogen evolution reaction

Meticulous tuning of nonprecious catalysts for overall water splitting is highly challenging but it is one of the most promising routes toward the future hydrogen economy. Here, we present a highly active, robust and earth abundant NiCoP electrocatalyst with a tuning capacity to excel in both oxygen and hydrogen evolution reactions. The composition of Ni and Co has been varied in a facile two-step method to produce coral-like NiCoP. The variant Ni0.25Co0.75 P has shown remarkable OER activity with overpotential as low as 240 mV at 10 mA/cm2 current density and Tafel slope of 68 mV dec−1 in alkaline medium. On the other hand, Ni0.75Co0.25P exhibited commendable HER performance with an overpotential of 120 mV and a Tafel slope of 123 mV dec−1 in an acid medium. Long-term durability and minimal loading of the catalyst ascertain the significance of the present catalyst. Moreover, our theoretical study finds that NiCoP provides a much higher electron density of d-states near the Fermi level compared to the individual metal phosphide and the low-index surface (100) of composite phosphide has a moderate level of desorption energy of oxygen and hydrogen compared to that of NiP2 & CoP corroborating the superiority of NiCoP in OER/HER performance.

Molybdenum-doped Co3S4 nanoarrays as outstanding catalysts for overall water splitting

Developing cobalt-based electrocatalysts that can replace precious metals is significant for hydrogen production in water splitting, however, this is still a complex and demanding task.

FeS Nanosheets Assembled with 1T-MoS2 Nanoflowers on Iron Foam for Efficient Overall Water Splitting

The exploration of highly efficient noble metal-free catalysts for overall water splitting is crucial for industrial application. In this work, FeS nanosheets/1T-MoS2 nanoflowers on conductive iron foam (IF) was prepared...

MnOx-decorated MOF-derived nickel-cobalt bimetallic phosphide nanosheet arrays for overall water splitting.

Exploring non-noble metal dual-functional electrocatalysts with high activity and stability for water splitting is highly desirable. In this study, using zeolitic imidazolate framework-L (ZIF-L) nanoarrays as the precursor, manganese oxide-decorated porous nickel-cobalt phosphide nanosheet arrays have been prepared on nickel foam (denoted as MnOx/NiCoP/NF) through cation etching, phosphorization and electrodeposition, which are utilized as an efficient dual-functional electrocatalyst for overall water splitting. The hierarchical porous nanosheet arrays provide abundant active sites for the electrochemical process, while the MnOx modification induces strong interfacial interaction, benefiting charge transfer. Thus, the MnOx/NiCoP/NF exhibits excellent electrocatalytic activity toward the hydrogen evolution reaction (HER, overpotential of 93 mV at 10 mA cm-2), oxygen evolution reaction (OER, overpotential of 240 mV at 10 mA cm-2) and overall water splitting (cell voltage of 1.59 V at 10 mA cm-2). Furthermore, it shows superior stability during continuous overall water splitting for 200 h. This work provides a simple and effective approach for developing efficient non-noble metal dual-functional catalysts for overall water splitting.

Nb2AlC MAX Nanosheets Supported Ru Nanocrystals as Efficient Catalysts for Boosting pH-Universal Hydrogen Production.

MAX phase combines both ceramic and metallic properties, which exhibits widespread application prospects. 2D MAX nanosheets have more abundant surface-active sites, being anticipated to improve the performance of surface-related applications. Herein, for the first time, 2D Nb2AlC nanosheets (NSs) as novel supports anchored with Ru catalysts for overall water splitting are developed. The optimized catalyst of Ru@Nb2AlC NSs exhibit Pt-comparable kinetics and superior catalytic activity toward hydrogen evolution reaction (HER) (low overpotentials of 61 and 169mV at 10 and 100mAcm-2, respectively) with excellent durability (5000 cycles or 80h) in alkaline media. In particular, Ru@Nb2AlC NSs achieve a mass activity of ≈4.8 times larger than the commercial Pt/C (20wt.%) catalyst. The post-oxidation resultant catalyst of RuO2@Nb2AlC NSs also exhibit boosting HER and oxygen evolution reaction activities and ≈100% Faraday efficiency for overall water splitting with a cell voltage of 1.61V to achieve 10mAcm-2. Therefore, the novel category of 2D MAX supports anchored with Ru nanocrystals offers a novel strategy for designing a wide range of MAX-supported metal catalysts for the renewable energy field.

Nanoarchitectonics of amorphous Fe–Ni–B nanosheets for high throughput overall water splitting reaction

Amorphous and defect rich Fe–Ni–B alloy nanosheets are developed which can efficiently catalyzes both the hydrogen and oxygen evolution reaction (HER, OER) at low overpotentials, making it an excellent bifunctional catalyst for overall water splitting (OWS) in 1.0 M and 30 wt% KOH electrolytes. The Fe1.0Ni1.0B||Fe1.0Ni1.0B electrode couple based electrolyzer can generates an exceptionally high current density of 1100 mA cm−2 and it offers 1.53 V cell voltage against 1.60 V for the crystalline counterpart for OWS at 10 mA cm−2, which are much lower than those of commercial Pt/C||IrO2. It also demonstrates long cycling stability of 6000 cycles and durability of 70 h, a high exchange current density, mass activity and Faradaic efficiency. The experimental and density functional theory (DFT) studies illustrate the coordination environment of the catalyst and showed corroboratively that modulation of electronic structure due to the amorphous and rich defect nature.

Immobilizing Bimetallic RuCo Nanoalloys on Few-Layered MXene as a Robust Bifunctional Electrocatalyst for Overall Water Splitting.

Doping Co atoms into Ru lattices can tune the electronic structure of active sites, and the conductive MXene can adjust the electrical conductivity of catalysts, which are both favorable for improving the electrocatalytic activity of the catalyst for water splitting. Here, ruthenium-cobalt bimetallic nanoalloys coupled with exfoliated Ti3 C2 Tx MXene (RuCo-Ti3 C2 Tx ) have been constructed by ice-templated and thermal activation. Due to the strong interaction between the RuCo nanoalloys and conductive MXene, RuCo-Ti3 C2 Tx not only exhibits an excellent hydrogen evolution reaction (HER) performance with a low overpotential and Tafel slope (60 mV, 34.8 mV dec-1 in 0.5 M H2 SO4 and 52 mV, 38.7 mV dec-1 in 1 M KOH), but also good oxygen evolution reaction (OER) performance in an alkaline electrolyte (266 mV, 111.1 mV dec-1 in 1 M KOH). The assembled RuCo-Ti3 C2 Tx ||RuCo-Ti3 C2 Tx electrolyzer requires a lower potential (1.56 V) than does the Pt/C||RuO2 electrolyzer at 10 mA cm-2 . A boosted catalytic HER activity from immobilizing the RuCo nanoalloys on MXene was unveiled by density functional theory calculations. This study provides a feasible and efficient strategy for developing MXene-based catalysts for overall water splitting.

Fe regulating Ni3S2/ZrCoFe-LDH@NF heterojunction catalysts for overall water splitting

With the continuous depletion of traditional energy sources, the development of sustainable energy sources has become one of the important tasks today. A two-step synthesis method was employed to construct Ni3S2/ZrCoFe-LDH@NF heterostructured electrocatalysts on nickel foam (NF) in situ. X-ray diffractometer, scanning electron microscope, transmission electron microscope, and X-ray electron spectroscopy were employed to characterize the Ni3S2/ZrCoFe-LDH@NF heterostructure, and the hydrogen-extraction reaction (HER), oxygen-extraction reaction (OER) and total hydrolysis properties of this electrocatalyst were tested in 1 mol·L−1 KOH electrolyte. It is shown that Ni3S2/ZrCoFe-LDH@NF is a lamellar stacked heterostructure with an overpotential of 330 mV and a Tafel slope of 90.9 mV·dec−1 at a current density of 100 mA·cm−2 in the OER reaction and 159.2 mV at a current density of 10 mA·cm−2 in the HER reaction. The Tafel slope is 96 mV·dec−1, and the catalyst exhibits good structural stability in the 100 h total hydrolysis stability test. The successful construction of this heterostructured electrocatalyst provides a good idea and research basis for the subsequent heterojunction and its application in electrocatalysis.

Atomically precise Au15Ag23 nanoclusters co-protected by alkynyl and bromine: Structure analysis and electrocatalytic application toward overall water splitting

We report the structure analysis and electrocatalytic application toward overall water splitting of atomically precise Au15Ag23(tBuC ≡ C)18Br6 nanoclusters (Au15Ag23 in short). Au15Ag23 possesses a triple-layered core-shell-shell metal core structure of Au6@Au6Ag23@Au3, with the core centre being a tetragonal bipyramidal Au6 structure unit, and the outer layer of one Ag atom linked with two alkynyl ligands to form a linear structural motif covering the surface of the metal nucleus. Au15Ag23 is a superatom with 14 free electrons and it displays a unique absorption profile. Remarkably, the Au15Ag23 catalyst exhibits excellent electrocatalytic properties in hydrogen evolution reaction (HER), manifested by a low overpotential of 125 mV at 10 mA cm−2 and a negligible current decrease for 16 h in 0.5 M H2SO4, while the Au15Ag23/NiFe-LDH catalyst demonstrates outstanding electrocatalytic performance in oxygen evolution reaction (OER), evidenced by an ultralow overpotential of 250 mV at 10 mA cm−2 and a ∼5% current decrease for 30 h in 1.0 M KOH. Such promoting effect is ascribed by the electron transfer from NiFe-LDH to the Au15Ag23 clusters, which results in generating high valent Fe species as active sites. When using the two catalysts for overall water splitting (OWS), only 1.51 V was required to achieve a current density of 10 mA cm−2, and it performed well in the 50 h's stability test. This study enriches the family member of alkynyl-protected AuAg bimetallic nanoclusters, and further highlights the dual functionalities (catalyzing HER and promoting OER) that metal nanoclusters can make contribution for electrochemical energy conversion and beyond.

A novel sea urchin like nanostructure as a bifunctional catalyst for overall water splitting

The aim of this study is to construct a high-activity platinum-anchored WO3 electrocatalyst and investigate the effect of platinum content on the catalytic performance. This strategy compared the electrocatalytic performance under acidic conditions by discussing the platinum content and significantly enhances the electrocatalytic activity through nanoscale structure creation and electronic synergies. Therefore, anchoring Pt atoms on WO3 nanoarrays is very important for boosting the activity and stability of electrocatalysis via a hydrothermal co-precipitation approach, Ptx/WO3@NF (x = 0.1 mmol∼0.3 mmol) named as Pt1/WO3, Pt2/WO3 and Pt3/WO3, which enhanced hydrogen evolution reaction(HER) and oxygen evolution reaction (OER) activities. The prepared Pt2/WO3@NF microspheres showed excellent electrocatalytic activity. When the current density was 10 mA cm−2, the HER overpotential was 77 mV, the OER overpotential was 126 mV, and the two-electrode water decomposition voltage was 1.4418 V. The bifunctional catalyst shows excellent stability, with virtually no decay in the curves after 100 h stability tests. In addition, nanosheet surface has abundant defects and interface structure, which can maintain excellent conductivity of catalyst and expose more active sites clarify the increased H2 adsorption for HER activity enhancement. The synthesis of a bifunctional electrocatalyst with both HER and OER properties, presents a novel and intriguing concept that contributes to the advancement of green hydrogen development.