Efficient Electrocatalysts For Overall Water Research Articles

Electronic-Structure Transformation of Platinum-Rich Nanowires as Efficient Electrocatalyst for Overall Water Splitting.

Platinum (Pt) has been widely used as cathodic electrocatalysts for the hydrogen evolution reaction (HER) but unfortunately neglected as an anodic electrocatalyst for the oxygen evolution reaction (OER) due to excessively strong bonding with oxygen species in water splitting electrolyzers. Herein we report that fine control over the electronic-structure and local-coordination environment of Pt-rich PtPbCu nanowires (NWs) by doping of iridium (Ir) lowers the overpotential of the OER and simultaneously suppresses the overoxidation of Pt in IrPtPbCu NWs during water electrolysis. In light of the one-dimensional morphology featured with atomically dispersed IrOx species and electronically modulated Pt-sites, the IrPtPbCu NWs exhibit an enhanced OER (175 mV at 10 mA cm-2) and HER (25 mV at 10 mA cm-2) electrocatalytic performance in acidic media and yield a high turnover frequency. For OER at the overpotential of 250 mV, the IrPtPbCu NWs show an enhanced mass activity of 1.51 A mg-1Pt+Ir (about 19 times higher) than Ir/C. For HER at the overpotential of 50 mV, NWs exhibit a remarkable mass activity of 1.35 A mg-1Pt+Ir, which is 2.6-fold relative to Pt/C. Experimental results and theoretical calculations corroborate that the doping of Ir in NWs has the capacity to suppress the formation of Ptx>4 derivates and ameliorate the adsorption free energy of reaction intermediates during the water electrolysis. This approach enabled the realization of a previously unobserved mechanism for anodic electrocatalysts.

Porous Prussian Blue Analogs Decorated Electrospun Carbon Nanofibers as Efficient Electrocatalyst for Overall Water Splitting

Metal-organic frameworks are becoming increasingly important in electrocatalysis as the hydrogen production sector grows. However, their electrocatalytic capability is limited by their inclination to agglomerate and the insufficient exposure of active sites. In this work, a three-step strategy was used to develop a bifunctional electrocatalyst with porous Prussian blue analogs supported on carbon nanofibers. The use of electrospun carbon nanofibers as conductive substrates can successfully address the problem of easy aggregation. Moreover, the etching procedure with tannic acid creates a porous structure that effectively regulates the electrical structure and exposes additional active sites. The resulting catalyst performs well in both the hydrogen evolution reaction and the oxygen evolution reaction, and also exhibits good stability in overall water splitting. The findings of this study present new concepts for the design and fabrication of metal-organic frameworks-based materials in the realm of electrocatalysis.

Synthesis of CoMoO4 Nanofibers by Electrospinning as Efficient Electrocatalyst for Overall Water Splitting.

To improve the traditional energy production and consumption of resources, the acceleration of the development of a clean and green assembly line is highly important. Hydrogen is considered one of the most ideal options. The method of production of hydrogen through water splitting constitutes the most attractive research. We synthesized CoMoO4 nanofibers by electrospinning along with post-heat treatment at different temperatures. CoMoO4 nanofibers show a superior activity for hydrogen evolution reaction (HER) and only demand an overpotential of 80 mV to achieve a current density of 10 mA cm-2. In particular, the CoMoO4 catalyst also delivers excellent performances of oxygen evolution reaction (OER) in 1 M KOH, which is a more complicated process that needs extra energy to launch. The CoMoO4 nanofibers also showed a superior stability in multiple CV cycles and maintained a catalytic activity for up to 80 h through chronopotentiometry tests. This is attributed mainly to a synergistic interaction between the different metallic elements that caused the activity of CoMoO4 beyond single oxides. This approach proved that bimetallic oxides are promising for energy production.

Component Engineering of Multiphase Nickel Sulfide-Based Bifunctional Electrocatalysts for Efficient Overall Water Splitting

The development of highly efficient and low-cost bifunctional electrocatalysts for water splitting has become increasingly attractive. So far, the strategies to optimize electrocatalytic performance have mainly focused on enhancing the active sites and regulating the surface structures through doping foreign metal or anions into the composites; however, the internal and external adjustments achieved by tuning the chemical composition and crystalline phases in a material in order to investigate the composition-dependent catalytic activity has generally remained limited. Here, through various in situ composition-dependent nickel sulfides grown while controlling the sulfidation degree, we achieve the precise regulation of nickel sulfides from a single-phase component to multiple-phase components (i.e., two-phase components and three-phase components), further comparing the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performances. Benefiting from the synergy of an analogous uniform nanoarray structure and excellent intrinsic activation, the as-obtained NixSy-5, with three-phase components, shows low overpotentials at 10 mA cm−2 for HER (148 mV) and OER (111 mV), as well as a low cell voltage of 1.48 V for overall water splitting in alkaline media, which are among the best results ever reported for overall water splitting.

Construction of Co2 P-Ni3 S2 /NF Heterogeneous Structural Hollow Nanowires as Bifunctional Electrocatalysts for Efficient Overall Water Splitting.

Designing efficient and stable transition metal-based catalysts for electrocatalytic water splitting is vital for the development of hydrogen production. Herein, a facile synthetic strategy is developed to fabricate transition metal-based heterogeneous structural Co2 P-Ni3 S2 hollow nanowires supported on nickel foam (Co2 P-Ni3 S2 /NF). Owing to the multiple active sites provided by transition metal compounds, large surface area of the unique hollow nanowire morphology, and the synergistic effect of Co2 P-Ni3 S2 heterostructure interfaces, Co2 P-Ni3 S2 /NF requires ultralow overpotentials of 110, 164mV for HER and 331.7, 358.3mV for OER at large current densities of 100, 500mA cm-2 in alkaline medium, respectively. Importantly, the two-electrode electrolyzer assembled by Co2 P-Ni3 S2 /NF displays a cell voltage of 1.54V at 10mA cm-2 and operates stably over 24h at 100mA cm-2 , which performs better than reported transition metal-based bifunctional electrocatalysts. This work presents a successful fabrication of transition metal-based bifunctional HER/OER electrocatalysts at large-current density and brings new inspiration for developing applicable energy conversion materials.

Fe-Doped NiSe Porous Nanosheets as Bifunctional Electrocatalysts for Efficient Overall Water Splitting

Fe-Doped NiSe Porous Nanosheets as Bifunctional Electrocatalysts for Efficient Overall Water Splitting

Ru-FeNi Alloy Heterojunctions on Lignin-derived Carbon as Bifunctional Electrocatalysts for Efficient Overall Water Splitting.

Rational design of efficient, stable, and inexpensive bifunctional electrocatalysts for oxygen evolution reactions (OER) and hydrogen evolution reactions (HER) is a key challenge to realize green hydrogen production via electrolytic water splitting. Herein, Ru nanoparticles and FeNi alloy heterojunction catalyst (Ru-FeNi@NLC) encapsulated via lignin-derived carbon was prepared by self-assembly precipitation and in situ pyrolysis. The designed catalyst displays excellent performance at 10 mA cm-2 with low overpotentials of 36 mV for HER and 198 mV for OER, and only needs 1.48 V for overall water splitting. Results and DFT calculations show the unique N-doped lignin-derived carbon layer and Ru-FeNi heterojunction contribute to optimized electronic structure for enhancing electron transfer, balanced free energy of reactants and intermediates in the sorption/desorption process, and significantly reduced reaction energy barrier for the HER and OER rate-determining steps, thus improved reaction kinetics. This work provides a new in situ pyrolysis doping strategy based on renewable biomass for the construction of highly active, stable and cost-effective catalysts.

Ru−FeNi Alloy Heterojunctions on Lignin‐derived Carbon as Bifunctional Electrocatalysts for Efficient Overall Water Splitting

AbstractRational design of efficient, stable, and inexpensive bifunctional electrocatalysts for oxygen evolution reactions (OER) and hydrogen evolution reactions (HER) is a key challenge to realize green hydrogen production via electrolytic water splitting. Herein, Ru nanoparticles and FeNi alloy heterojunction catalyst (Ru−FeNi@NLC) encapsulated via lignin‐derived carbon was prepared by self‐assembly precipitation and in situ pyrolysis. The designed catalyst displays excellent performance at 10 mA cm−2 with low overpotentials of 36 mV for HER and 198 mV for OER, and only needs 1.48 V for overall water splitting. Results and DFT calculations show the unique N‐doped lignin‐derived carbon layer and Ru−FeNi heterojunction contribute to optimized electronic structure for enhancing electron transfer, balanced free energy of reactants and intermediates in the sorption/desorption process, and significantly reduced reaction energy barrier for the HER and OER rate‐determining steps, thus improved reaction kinetics. This work provides a new in situ pyrolysis doping strategy based on renewable biomass for the construction of highly active, stable and cost‐effective catalysts.

Ni-Activated and Ni-P-Activated Porous Titanium Carbide Ceramic Electrodes as Efficient Electrocatalysts for Overall Water Splitting.

Developing electrocatalysts based on transition-metal carbides that can be utilized for commercial water splitting is a challenging endeavor. To address this challenge, we employed a novel approach that merged phase-inversion tape-casting and sintering, subsequently implementing a simple and efficient electrodeposition process, to synthesize Ni-activated and Ni-P-activated titanium carbide (Ni/TiC, Ni-P/TiC) ceramic electrodes as water splitting catalytic cathodes and anodes. These self-supported Ni/TiC and Ni-P/TiC electrodes are binder-free with abundant finger-like pores, which contribute to the formation of highly conductive skeleton and more exposed active sites for direct water splitting. These catalysts exhibit outstanding performance, superior to many reported bifunctional nickel-based catalysts supported on other substrates. Moreover, the exceptional electrocatalytic performance of the Ni/TiC and Ni-P/TiC catalysts is attributed to the synergistic effect between Ni oxides (phosphides) and TiC, as revealed by density functional theory (DFT) calculations. This self-template strategy paves the way for fabricating industrially applicable electrodes to generate hydrogen and oxygen through water splitting.

Collaborative Interface Optimization Strategy Guided Ultrafine RuCo and MXene Heterostructure Electrocatalysts for Efficient Overall Water Splitting.

Developing highly active and robust electrocatalysts for the hydrogen/oxygen evolution reaction (HER/OER) is crucial for the large-scale utilization of green hydrogen. In this study, a collaborative interface optimization guided strategy was employed to prepare a metal-organic framework (MOF) derived heterostructure electrocatalyst (MXene@RuCo NPs). The obtained electrocatalyst requires overpotentials of only 20 mV for the HER and 253 mV for the OER to deliver a current density of 10 mA/cm2 in alkaline media, respectively, and it also exhibits great performance at high current density. Experiments and theoretical calculations reveal that the doped Ru introduces second active sites and decreases the diameter of nanoparticles, which greatly enhances the number of active sites. More importantly, the MXene/RuCo NPs heterogeneous interfaces in the catalysts exhibit great synergistic effects, decreasing the work function of the catalyst and improving the charge transfer rate, thus reducing the energy barrier of the catalytic reaction. This work represents a promising strategy for the development of MOF-derived highly active catalysts to achieve efficient energy conversion in industrial applications.

2D Ni‐Naphthalene‐2,6‐Dicarboxylic Acid Metal‐Organic Framework as Electrocatalysts for Efficient Overall Water Splitting

Two‐dimensional metal‐organic frameworks (MOFs) are regarded as promising electrocatalysts because of their high surface area and tunable compositions. Herein, a novel nickel‐based 2D MOF for efficient oxygen evolution reaction (OER) has been developed. Ni‐NDC MOF nanosheets (NDC = naphthalene‐2,6‐dicarboxylic acid) are successfully synthesized on a nickel foam (NF) through a surfactant‐assisted one‐step hydrothermal method. The resulting Ni‐NDC@NF possessing a high electrochemically active surface area of 3.06 mF cm−2 exhibits excellent OER performance with a low overpotential of 249 mV at 10 mA cm−2, a small Tafel slope of 74 mV dec−1, 100% faradaic efficiency, and long‐term stability of 24 h at least. For the application of a bifunctional catalyst, NiMo alloy is electrodeposited on the Ni‐NDC@NF to enhance hydrogen evolution reaction activity. The overall water splitting in a two‐electrode configuration of NiMo/Ni‐NDC@NF electrodes as both anode and cathode require only a 1.56 V for 20 mA cm−2. The photovoltaic‐electrocatalysis system powered by the tandem solar cell represents a high solar‐to‐hydrogen efficiency of ≈22%. This work will contribute to inspiring the design of novel MOF composite catalysts using vertically aligned 2D MOF nanosheet architecture, thereby enlarging the potential of MOFs on next‐generation electrocatalysts and energy devices.

MoS2/NiFeS2 heterostructure as a highly efficient electrocatalyst for overall water splitting at high current densities

MoS2/NiFeS2 heterostructure as a highly efficient electrocatalyst for overall water splitting at high current densities

Hydrogen-Bond Regulation of the Microenvironment of Ni(II)-Porphyrin Bifunctional Electrocatalysts for Efficient Overall Water Splitting.

Accurately regulating the microenvironment around active sites is an important approach for boosting the overall water splitting performance of bifunctional electrocatalysts,whichcan drive both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) in the same electrolyte. Herein, pseudo-pyridine-substituted Ni(II)-porphyrins (o-NiTPyP, m-NiTPyP, and p-NiTPyP) with pseudo-pyridine N-atoms located at the ortho-, meta-, or para-position are prepared and used as model catalysts for alkaline water splitting. Experimental and theoretical results reveal that the pseudo-pyridine N-atom positions can regulate the microenvironment around the active sites and the adsorption free energy of H-donating substances by affecting the H-bonding interaction and the NNiN bond angles of active sites, and thus those pseudo-pyridine-substituted Ni(II)-porphyrins deliver better electrocatalytic activity than the Ni(II)-tetraphenylporphyrin (NiTPP) without pseudo-pyridine N-atoms. Among them, m-NiTPyP on carbon nanotubes delivers the lowest overpotentials of 267 and 138mV at 10mA cm-2 for the OER and HER, respectively. Specifically, m-NiTPyP as bifunctional electrocatalyst in an alkaline electrolyzer requires only 1.62V to drive efficient overall water splitting at 10mA cm-2 while remaining durable. This work proposes a new H-bond-regulating approach of the microenvironment of electrocatalysts for effectively boosting the overall water splitting activity and deeply understanding its related mechanism.

MoS2/NiSe2/rGO Multiple-Interfaced Sandwich-like Nanostructures as Efficient Electrocatalysts for Overall Water Splitting

Constructing a heterogeneous interface using different components is one of the effective measures to achieve the bifunctionality of nanocatalysts, while synergistic interactions between multiple interfaces can further optimize the performance of single-interface nanocatalysts. The non-precious metal nanocatalysts MoS2/NiSe2/reduced graphene oxide (rGO) bilayer sandwich-like nanostructure with multiple well-defined interfaces is prepared by a simple hydrothermal method. MoS2 and rGO are layered nanostructures with clear boundaries, and the NiSe2 nanoparticles with uniform size are sandwiched between both layered nanostructures. This multiple-interfaced sandwich-like nanostructure is prominent in catalytic water splitting with low overpotential for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) and almost no degradation in performance after a 20 h long-term reaction. In order to simulate the actual overall water splitting process, the prepared nanostructures are assembled into MoS2/NiSe2/rGO||MoS2/NiSe2/rGO modified two-electrode system, whose overpotential is only 1.52 mV, even exceeded that of noble metal nanocatalyst (Pt/C||RuO2~1.63 mV). This work provides a feasible idea for constructing multi-interface bifunctional electrocatalysts using nanoparticle-doped bilayer-like nanostructures.

Heterogeneous Fe-Doped NiCoP-MoO3 Efficient Electrocatalysts for Overall Water Splitting.

Transition metal phosphides with excellent performance are one of the effective alternatives to noble metal catalysts in overall water splitting. In this paper, the Fe-NiCoP-MoO3 composite was prepared by a facile synthesis as the bifunctional electrocatalyst. Fe-NiCoP-MoO3 achieves an operating current density of 10 mA/cm2 at a low overpotential of 65 mV for hydrogen evolution reaction and drives an operating current density of 50 mA/cm2 at only 293 mV for oxygen evolution reaction. Significantly, Fe-NiCoP-MoO3 was employed as the anode and cathode for overall water splitting, which only requires a cell voltage of 1.586 V to reach 10 mA/cm2 as well as shows excellent stability. The electrocatalytic activity of Fe-NiCoP-MoO3 exceeds most of the recently reported typical bifunctional electrocatalysts. This may be due to the coupling effect between the polymetallic phosphides. In addition, heterogeneous catalysts generally expose more active sites than homogeneous catalysts. In addition, replacing MoO3 with WO3 and VO3 can also improve the performance of Fe-NiCoP. This work provides an idea for the modification of phosphides.

Structural and Electronic Modulation of Iron-Based Bimetallic Metal-Organic Framework Bifunctional Electrocatalysts for Efficient Overall Water Splitting in Alkaline and Seawater Environment.

Metal-organic frameworks (MOFs) are considered potential electrocatalysts for efficient water splitting. However, the structure-activity relationship of most MOFs is not systematically analyzed for electrocatalysis for anodes and cathodes. In this paper, we provide a strategy to modulate the electronic microstructure of iron-based bimetallic MOFs (MFe-BDC (M: Mg, Zn, Cd)) grown on the nickel foam (NF) as bifunctional electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The optimal bimetallic CdFe-BDC via modulating appropriate metal cations of IIA and IIB possesses excellent OER and HER performance with the lowest overpotentials of 290 mV at 100 mA cm-2 and 148 mV at 10 mA cm-2, respectively. The overall water splitting performance of the as-prepared CdFe-BDC requires 1.68 V to achieve a current density of 10 mA cm-2 in the real seawater media, and it exhibits the competitive H2 and O2 production rates of 6.4 and 3.1 μL s-1, respectively, in ambient alkaline conditions, suggesting its potential practical applications. Density functional theory (DFT) calculations demonstrate the relationship between microstructure and electrocatalytic performance of bimetallic MFe-BDC. This work emphasizes the significance of tailoring the electronic microstructure of bimetallic MOFs for efficient overall water splitting in alkaline and seawater environment.

FeCoNiB Nanoparticles Anchoring on Vertically Aligned B-Doped Graphene Array as an Efficient Electrocatalyst for Overall Water Splitting

Research on cost-effective and high-efficient catalysts for overall water splitting is urgent, and iron group metal borides (IMBs) are a promising candidate. Here, FeCoNiB nanoparticles anchoring on vertically aligned B-doped graphene array (FeCoNiB/BVG) by electroless plating are synthesized for overall water splitting, and FeCoNiB nanoparticles anchoring on other heteroatom-doped graphene substrates (FeCoNiB/XVG, X = N, P, S, O) are prepared for comparison. FeCoNiB/BVG exhibits the best performance with HER and OER overpotential of only 88 mV and 149 mV in 1.0 M KOH, respectively. And FeCoNiB/BVG has a very strong stability for 15 h and the Faraday efficiency of about 94%. The XPS results prove that the best performance of FeCoNiB/BVG is due to the synergistic effect between B in BVG and B in FeCoNiB. This work provides a reference for the rational design of non-noble metal-based electrocatalysts and promotes the application of non-noble metal-based electrocatalysts in the water electrolysis industry.

Electric-Field-Treated Ni/Co3O4 Film as High-Performance Bifunctional Electrocatalysts for Efficient Overall Water Splitting

HighlightsA novel physical approach is proposed to enhance the electrocatalytic performance by electric field.Under the action of electric field, some stable conductive filaments consisting of oxygen vacancies are formed in the Ni/Co3O4 film, which remarkably reduces the system resistivity.The electric-field-treated Ni/Co3O4 material exhibits significantly superior activity and stability as a bifunctional electrocatalyst for overall water splitting, and its performance exceeds the state-of-the-art electrocatalysts.Rational design of bifunctional electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) with excellent activity and stability is of great significance, since overall water splitting is a promising technology for sustainable conversion of clean energy. However, most electrocatalysts do not simultaneously possess optimal HER/OER activities and their electrical conductivities are intrinsically low, which limit the development of overall water splitting. In this paper, a strategy of electric field treatment is proposed and applied to Ni/Co3O4 film to develop a novel bifunctional electrocatalyst. After treated by electric field, the conductive channels consisting of oxygen vacancies are formed in the Co3O4 film, which remarkably reduces the resistance of the system by almost 2 × 104 times. Meanwhile, the surface Ni metal electrode is partially oxidized to nickel oxide, which enhances the catalytic activity. The electric-field-treated Ni/Co3O4 material exhibits super outstanding performance of HER, OER, and overall water splitting, and the catalytic activity is significantly superior to the state-of-the-art noble metal catalysts (Pt/C, RuO2, and RuO2 ǁ Pt/C couple). This work provides an effective and feasible method for the development of novel and efficient bifunctional electrocatalyst, which is also promising for wide use in the field of catalysis.

Hierarchical Core-Shell Structural Ni2p/Nimoo4@Cop/Fep2 Nanorods as Difunctional Electrocatalysts for Efficient Overall Water Splitting

Hierarchical Core-Shell Structural Ni2p/Nimoo4@Cop/Fep2 Nanorods as Difunctional Electrocatalysts for Efficient Overall Water Splitting

Engineering Heterostructure of Bimetallic Nickel-Silver Sulfide as an Efficient Electrocatalyst for Overall Water Splitting in Alkaline Media

Engineering Heterostructure of Bimetallic Nickel-Silver Sulfide as an Efficient Electrocatalyst for Overall Water Splitting in Alkaline Media