Catalysts For Overall Water Splitting Research Articles

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.

Experimental and DFT study of the MoO2@Fe2O3 catalyst for overall water splitting in acidic and alkaline electrolytes

HER: overpotential for HER, OER: overpotential for OER; Rs: solution resistance, Rct: charge transfer resistance. The comparison of various parameters of the MoO2@Fe2O3 electrode in KOH and H2SO4 electrolytes.

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.

Bimetallic atom-improved Ni3S2 bifunctional electrocatalysts for efficient hydrogen evolution reaction and overall water splitting performance

An efficient bifunctional Ni3S2–Fe–Ni electrocatalyst was prepared by two-step methods. DFT calculations indicate that the adsorption energy of the catalyst for overall water-splitting was modulated due to the introduction of Fe and Ni atoms.

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.

Fe Cluster Modified Co9 S8 Heterojunction: Highly Efficient Photoelectrocatalyst for Overall Water Splitting and Flexible Zinc-Air Batteries.

Designing bifunctional low-cost photo-assisted electrocatalysts for converting solar and electric energy into hydrogen energy remains a huge challenge. Herein, a heterojunction (Fe cluster modified Co9 S8 loaded on carbon nanotubes, Co9 S8 -Fe@CNT)for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is demonstrated. Benefiting from the good electronic conductivity and spatial confinement of the carbon skeleton, as well as the electronic structure regulation of the Fe cluster, Co9 S8 -Fe@CNT exhibits excellent catalytic performance with a low overpotential of 150mV for OER and 135mV for HER at 10mAcm-2 . Upon light irradiation, holes and electrons are generated in the valence band and conduction band of the Co9 S8 , respectively. Part of the charges are transferred to the interface to facilitate the catalytic reaction, while the remaining are transferred by the electrode. When working as a bifunctional catalyst for overall water splitting, the performance can reach 1.33V at under light conditions, which is significantly better than 1.52V in a dark environment. Theoretical calculations revealed lowered Gibbs free energy (∆GH *) of the heterojunction with the effect of Fe modification of Co9 S8 . This work sheds a new light in designing novel photoelectrochemical materials to convert solar and electric energy into chemical energy.

Phosphidation treatment of surfactant-tuned iron polyphthalocyanine grown in situ on nickel foam: An efficient bifunctional catalyst for overall water splitting

Developing robust electrocatalysts for overall water splitting is vital for industrial hydrogen production on a large scale. Herein, we obtain a bifunctional electrocatalyst NF@FePPc-s/p (where s represents surfactant and p stands for the phosphidation treatment) by phosphorization of surfactant (F127)-tuned iron polyphthalocyanine (FePPc) grown in situ on the nickel foam (NF) substrate. The as-obtained NF@FePPc-s/p exhibits the golden needle mushroom-like morphology, which is conducive to fully exposing the active sites and boosting the electron-transfer kinetics at the reaction interface. The physicochemical characterization and electrochemical measurements demonstrate that the active Fe2P and Ni2P phases formed during the phosphidation treatment are intrinsically active catalytic sites for hydrogen evolution reaction (HER), and the FeOOH formed from phase transformation of Fe2P during the oxygen evolution reaction (OER) process contributes a lot to enhancement of the OER activity. Furthermore, the electronic interaction between Fe and Ni further improves the electrocatalytic performances for both reactions. The optimized NF@FePPc-s/p catalyst exhibits remarkable OER (293 mV@100 mA cm−2) and HER (190 mV@100 mA cm−2) activities in 1.0 M KOH electrolyte. The water electrolyzer assembled with the NF@FePPc-s/p as the cathode and anode electrodes, respectively, only requires a low cell voltage of 1.743 V to obtain the current density of 100 mA cm−2 for overall water splitting, outperforming the precious NF@RuO2–Pt/C based electrolyzer (1.852 V).

Crystalline/Amorphous Mo-Ni(OH)2/FexNiy(OH)3x+2y hierarchical nanotubes as efficient electrocatalyst for overall water splitting

The development of efficient bifunctional catalysts for overall water splitting is highly desirable and essential for the advancement of hydrogen technology. In this work, Mo-Ni(OH)2/FexNiy(OH)3x+2y with hierarchical nanotube structure is constructed on flexible carbon cloth (CC) through simple electrochemical deposition and hydrothermal method. The hollow tube-structure is in favor of both exposing active sites and enhancing mass transfer capability. Moreover, the doping of Mo can enhance the electronic conductivity of heterostructures. The interfacial interaction between amorphous and crystal can enhance effectively the charge transfer kinetics across the interface. Therefore, Mo-Ni(OH)2/FexNiy(OH)3x+2y can achieve a low overpotential of 57 mV for hydrogen evolution reaction (HER) and 229 mV for oxygen evolution reaction (OER) at 10 mA·cm−2. In addition, Mo-Ni(OH)2/FexNiy(OH)3x+2y needs a potential of only 1.54 V at 10 mA·cm−2 for overall water splitting, and retains for a long period of time (60 h) reliable. The work will provide a valuable approach to the construction of highly efficient electrocatalysts for overall water splitting.

Low‐Iridium‐Content IrIn2 Intermetallics with an Unconventional Face‐Centered Orthorhombic Phase for Efficient Overall Water Splitting

AbstractIridium (Ir) is an efficient catalyst for overall water splitting, yet its widespread utilization is hampered by the substantial cost and limited stability. Alloying Ir with heteroatoms can optimize the electronic structure of the catalyst and reduce the required amount of Ir. Compared to solid solution alloys, Ir‐based intermetallic compounds (IMCs) with ordered and stronger Ir‐heteroatom bonds exhibit superior catalytic activity and durability. Hence, adjusting the crystal structure of Ir‐based IMCs is expected to further optimize the configurations of catalytic active sites with minimal usage of Ir. Here, IrIn2 IMCs with unconventional face‐centered orthorhombic structure are synthesized by a high‐temperature annealing reduction method, in which the atomic percentage of Ir is only 33%. The calculation results show that the d‐band center of IrIn2 is shifted upward compared to metallic Ir, resulting in enhanced adsorption with intermediates. Meanwhile, the formation of ordered Ir─In bonds improves the charge transfer effectively and makes the IrIn2 IMCs resistant to atom migration and dissolution during the electrochemical reactions. For overall water splitting, the cell voltage required to achieve 10 mA cm−2 is as low as 1.51 V under acidic condition. And IrIn2 IMCs exhibit excellent durability, with no degradation in performance >55 h.

Interface and morphology engineering of Ru-FeCoP hollow nanocages as alkaline electrocatalyst for overall water splitting

Interface and Morphology engineering strategies of electrocatalysts are of great importance to promote water splitting performance, although still facing many challenges. In this work, we present a facile method for preparing Ru-anchored hollow FeCoP nanocages electrocatalyst with ultrathin sheets. The hollow structure composed of ultrathin nanosheets and rich heterogeneous interfaces benefit the as-synthesized catalyst to exhibit small overpotentials of 310 mV and 94 mV at the current density of 10 mA·cm−2 for oxygen evolution reaction and hydrogen evolution reaction, respectively. When Ru-FeCoP nanocages were employed as the bifunctional catalyst for overall water splitting, the potential of 1.65 V was obtained to reach the current density of 10 mA·cm−2. The experimental results confirmed that the formation of hierarchical hollow structure facilitated the exposure of active sites and enhanced the electrocatalytic activity. Meanwhile, XPS and DFT data also reveal that the presence of heterogeneous interfaces changed the electronic structure, optimized the absorption of the intermediates, significantly reduced the energy barrier of water dissociation and promoted the release of H2. This work offers an effective route for rational design of low-loading noble metal-anchored metal phosphide with the hierarchical hollow structure and rich interfaces towards overall water splitting.

Constructing defect-rich S-doped NiMoO4/Ni3S2 2D/2D heterostructures as highly efficient and stable bifunctional electrocatalysts for overall water splitting

The development of economical, efficient, and durable bifunctional catalyst for overall water splitting is an attractive and challenging task. Herein, a novel defect-rich 2D/2D heterostructure is constructed by vertically growing S-doped NiMoO4 (NiMoO4-S) nanosheets on nickel sulfide (Ni3S2) nanosheet arrays supported on nickel foam (NF) using a two-step hydrothermal method. Benefiting from the hierarchical sheet-on-sheet heterogeneous nanostructure and abundant oxygen vacancies for more active sites, efficient electronic/mass transfer, and fast gas release, the synthesized NiMoO4-S/Ni3S2/NF electrode exhibits excellent electrocatalytic performance for HER (η10 mA cm−2 = 107 mV) and OER (η50 mA cm−2 = 285 mV). The alkaline water electrolyzer with NiMoO4-S/Ni3S2/NF as the positive and negative electrodes can provide a current density of 10 mA cm−2 with the potential of 1.52 V, which is below that of the commercial Pt||RuO2/NF system or many other reported systems. More importantly, the alkaline water electrolyzer offers a current density of 100 mA cm−2 at 1.85 V with outstanding durability of over 50 h. This research points to a promising route in designing transition metal-based bifunctional electrocatalysts for large-scale energy conversion applications.

Ruthenium‐Induced Activation of Molybdenum‐Cobalt Phosphide for High‐Efficiency Water Splitting

AbstractAdvancing green hydrogen production technologies relies heavily on the development of highly efficient and durable bifunctional catalysts for overall water splitting. Herein, this study reports the ruthenium‐modified hollow cubic molybdenum‐cobalt phosphide (Ru‐MoCoP) as exceptional performance electrocatalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Theoretical calculations and experimental results indicate that the incorporation of Ru not only serves as an efficient active site, but also adjusts the electronic structure and improves the reactivity of the original sites, as well as generates more phosphorus vacancies, which improves the electrical conductivity and exposes more active sites. Benefiting from the advantages triggered by the incorporation of Ru mentioned above, the Ru‐MoCoP delivers low overpotentials of 55 and 240 mV at 10 mA cm−2 for HER and OER, respectively. Furthermore, the electrolyzer assembled with Ru‐MoCoP achieves a current density of 50 mA cm−2 at 1.6 V and can be operated stably for 150 h. Notably, the assembled two‐electrode system can be powered by a single commercial AA battery, accompanied with evident gas bubble evolution. This research proposes a promising strategy for the development of highly efficient bifunctional phosphide catalysts, aiming to achieve efficient energy conversion in a wide range of industrial applications.

In situ synthesis of self-supported Ir/IrO2 heterostructures via Ar-H2 plasma as efficient bifunctional catalyst for overall water splitting in acidic media

Iridium oxide (IrO2) has been intensively investigated as an efficient and stable anode catalyst for the oxygen evolution reaction (OER) in water splitting system. However, the overall water splitting performance of IrO2 is rarely studied because of its strong adsorption of hydrogen intermediates during the hydrogen evolution reaction (HER) process. Herein, a facile Ar/H2 plasma reduction strategy is developed to activate the HER performance of self-supported IrO2 by constructing a novel metal/oxide heterostructure. The in-situ synthesized Ir/IrO2 composite possesses excellent electrical interconnection and abundant catalytic active sites. Meanwhile, dual active sites induced by the strong interface effect between metallic Ir and IrO2 could optimize the adsorption energy and reaction path for both HER and OER. The optimized Ir–IrO2/Ti@Ar–H2 exhibits remarkable activities with a small overpotential of 58 and 211 mV toward HER and OER, respectively. Besides, Ir–IrO2/Ti@Ar–H2||Ir–IrO2/Ti@Ar–H2 electrolyzer only requires an operational voltage of 1.48 V to afford a current density of 10 mA cm−2, much lower than that of commercial Pt/C||IrO2 (1.61 V).

Carbon dots-coupled with urchin-like tungsten-doped CoP as efficient bifunctional electrocatalysts for overall water splitting

Developing readily-available, highly-efficient and stable electrocatalysts for water splitting is a challenge. Herein, a novel non-precious metal catalyst via coupling the N-doped carbon dots (NCDs) with the W doped CoP that is assembled on Ni foam (Wy-CoP@NCDsx/NF) has been developed as the efficient bifunctional catalysts for overall water splitting. Specifically, the optimal W0.03-CoP@NCDs0.5/NF catalyst exhibits typical urchin shape under the regulation of the NCDs, showing abundant active sites. Meanwhile, the W-doping modulates the electronic structure and lowers the energy barrier of the catalyst. Moreover, the porous Ni foam as the catalyst supporter enables to expose catalyst more active sites and accelerate electron transfer. Beneficially, the optimal W0.03-CoP@NCDs0.5/NF only requires 136 mV and 305 mV overpotentials in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) to reach the current density of 100 mA·cm−2 in 1.0 M KOH, respectively. More importantly, the electrolyzer assembled by such W0.03-CoP@NCDs0.5/NF consumes a cell potential as low as 1.664 V to afford a large current density of 100 mA·cm−2 with remarkable stability, which offers great promise for practical applications.