Efficient Oxygen Evolution Electrocatalysts Research Articles

Mo/Fe bimetallic pyrophosphates derived from Prussian blue analogues for rapid electrocatalytic oxygen evolution

Efficient and stable oxygen evolution electrocatalysts are indispensable for industrial applications of water splitting and hydrogen production. Herein, a simple and practical method was applied to fabricate (Mo, Fe)P2O7@NF electrocatalyst by directly growing Mo/Fe bimetallic pyrophosphate derived from Prussian blue analogues on three-dimensional porous current collector. In alkaline media, the developed material possesses good hydrophilic features and exhibits best-in-class oxygen evolution reaction (OER) performances. Surprisingly, the (Mo, Fe)P2O7@NF only requires overpotentials of 250 and 290 mV to deliver 100 and 600 mA cm−2 in 1 mol L−1 KOH, respectively. Furthermore, the (Mo, Fe)P2O7@NF shows outstanding performances in alkaline salty water and 1 mol L−1 high purity KOH. A worthwhile pathway is provided to combine bimetallic pyrophosphate with commercial Ni foam to form robust electrocatalysts for stable electrocatalytic OER, which has a positive impact on both hydrogen energy application and environmental restoration.

PANI coated NiMoOP nanoarrays as efficient electrocatalyst for oxygen evolution

To obtain high-efficiency and affordable electrocatalysts for water splitting application, constructing specific nanostructures is believed as an effective solution to pursue advanced structure characteristics for improved catalysis property. In this work, a shell-core structured catalyst of polyaniline coated hybrid Ni3Mo2P-MoO3 nanoarrays is designed for oxygen evolution. The polyaniline shell not only assures merit of high conductivity for accelerated charge transfer, but also benefits the catalysis stability. The coupling effect between nitrogen species of polyaniline shell and metals of core materials imparts improved intrinsic catalysis activity and more active sites. Hence, the present sample manifests excellent catalytic efficiency for alkali water oxidation, only needing low overpotentials of 290 and 412 mV at high current densities of 100 and 400 mA cm−2, respectively. The development of shell-core catalyst using polyaniline as shell material paves a way for activating other transition metal catalytic materials and supplies a basis for industrial water splitting applications.

Advances in Oxygen Evolution Electrocatalysts for Proton Exchange Membrane Water Electrolyzers

AbstractProton exchange membrane water electrolyzer (PEMWE) technology is of interest in the context of electrocatalytic hydrogen generation from renewable energies. It has the benefits of immediate response, higher proton conductivity, lower ohmic losses, and gas crossover rate. One key step toward to large‐scale application, is the development of highly efficient, durable, and compatible anodic oxygen evolution electrocatalysts in acidic media to decrease the usage of expensive and scarce precious metals. Within this scenario, an in‐depth understanding of oxygen evolution reaction mechanisms including the adsorption evolution mechanism and lattice oxygen evolution mechanism is first provided to aid development of innovative materials and elucidate the origin of catalyst degradation. Second, recent progress in the development of oxygen evolution electrocatalysts in acid media is reviewed with an emphasis on the underlying structure–performance relationships. Third, the current application status and research progress in PEMWEs along with representative examples are discussed. Last, the remaining challenges and promising insights are proposed to inspire future studies on the development of hydrogen production technology from renewable energy.

Biomass Chitosan-Deriving Co-Induced N-Doped Carbon Nanotubes to Support Mn 3 O 4 As Efficient Electrocatalysts for Oxygen Reduction and Oxygen Evolution

Biomass Chitosan-Deriving Co-Induced N-Doped Carbon Nanotubes to Support Mn 3 O 4 As Efficient Electrocatalysts for Oxygen Reduction and Oxygen Evolution

Steps towards highly-efficient water splitting and oxygen reduction using nanostructured β-Ni(OH)2.

β-Ni(OH)2 nanoplatelets are prepared by a hydrothermal procedure and characterized by scanning and transmission electron microscopy, X-ray diffraction analysis, Raman spectroscopy, and X-ray photoelectron spectroscopy. The material is demonstrated to be an efficient electrocatalyst for oxygen reduction, oxygen evolution, and hydrogen evolution reactions in alkaline media. β-Ni(OH)2 shows an overpotential of 498 mV to reach 10 mA cm−2 towards oxygen evolution, with a Tafel slope of 149 mV dec−1 (decreasing to 99 mV dec−1 at 75 °C), along with superior stability as evidenced by chronoamperometric measurements. Similarly, a low overpotential of −333 mV to reach 10 mA cm−2 (decreasing to only −65 mV at 75 °C) toward hydrogen evolution with a Tafel slope of −230 mV dec−1 is observed. Finally, β-Ni(OH)2 exhibits a noteworthy performance for the ORR, as evidenced by a low Tafel slope of −78 mV dec−1 and a number of exchanged electrons of 4.01 (indicating direct 4e−-oxygen reduction), whereas there are only a few previous reports on modest ORR activity of pure Ni(OH)2.

Fe–Co–Ni trimetallic organic framework chrysanthemum-like nanoflowers: efficient and durable oxygen evolution electrocatalysts

The preparation process of a trimetallic FCN-BTC MOF and its OER catalytic performance compared with the noble metal catalyst RuO2.

Cu/Co/CoS2 embedded in S,N-doped carbon as highly efficient oxygen reduction and evolution electrocatalyst for rechargeable zinc–air batteries

The synergistic interaction induced by multiphase interfaces between Cu, Co, CoS2 and S,N–C leads to excellent bifunctional oxygen reduction and evolution reaction activity and durability.

Fe-Ni co-doping strategy in perovskite for developing an efficient oxygen evolution electrocatalyst

The high reaction barrier of the oxygen evolution reaction (OER) has always been the bottleneck of the water decomposition reaction, so low-cost, high-performance and stable catalysts are urgently needed currently. Herein, we designed an effective OER electrocatalyst BaCo0.6Fe0.2Ni0.2O3−δ (BCFN) by a codoping strategy. The overpotential of BCFN at a current density of 10 mA/cm2 reaches 310 mV, and possesses a Tafel slope of 50.2 mV/dec. The catalytic capability of BCFN is much stronger than that of Fe-doped BaCo0.8Fe0.2O3−δ (360 mV), Ni-doped BaCo0.8Ni0.2O3−δ (375 mV), and benchmark IrO2 with excellent performance (329 mV). At the same time, BCFN is also a fairly stable alkaline OER catalyst. After 500-cycle scans, BCFN still shows high catalytic activity without significant decrease in catalytic performance. Electrochemical experiments show that BCFN has the fastest reaction kinetics and the lowest charge transfer resistance among the materials in this work. In addition, a large amount of highly oxidative oxygen O22−/O− and hydroxyl groups OH− on the surface of BCFN are conducive to the occurrence of OER, thereby increasing the reaction rate. This work provides a universal strategy to develop high-performance electrocatalysts for electrochemical energy conversion technology.

Fullerene nanorods supported cobalt nickel sulfide composite as efficient electrocatalyst for oxygen evolution

New types of clean and renewable energy conversion and storage technologies such as water electrolysis, fuel cells and metal-air batteries have brought new hopes for solving the world's increasingly serious energy shortage and pollution problems. These electrochemical technologies include important electrode reactions, such as hydrogen evolution reaction (HER), and oxygen evolution reaction (OER). However, the slow kinetics of OER has become a bottleneck restricting the overall efficiency of water splitting. The state-of-the-art OER catalysts are mainly based on Pt, Ir, and Ru in commercial applications today, which are expensive and lack of reserves. Therefore, researchers are working hard to develop highly active and stable non-noble metal compounds as alternatives. In this work, we constructed a novel hybrid nanostructure with ultra-small cobalt nickel sulfide nanoparticles decorated on PVP-modified solvent-free fullerene nanorod (sf-FNR-PVP/CoNi2S4). Benefiting from the efficient charge transfer from CoNi2S4 to FNR matrix, the hybrid material exhibited enhanced OER activity during the electrocatalytic reaction. Impressively, the Tafel slope of sf-FNR-PVP/CoNi2S4 was 82 mV dec−1, and the charge transfer resistance is 74.2 Ω, much better than that of CoNi2S4. Besides, the sf-FNR-PVP/CoNi2S4 exhibited robust electrocatalytic durability. This work provides new opportunity for fullerenes in the field of energy conversion and storage.

Efficient NiFe-based oxygen evolution electrocatalysts and origin of their distinct activity

Efficient oxygen evolution reaction (OER) electrocatalyst is essential for water electrolysis. Herein, high-performance NiFe-based layered double hydroxides (LDH), phosphide and sulfide OER pre-catalysts were fabricated and their distinct activity was unveiled. The as-prepared NixFe1−xS exhibits ultralow OER overpotential of 122 mV at 10 mA cm−2 in 1 M KOH. The alkali-electrolyzer using NixFe1−xS electrodes achieve superior performance exhibiting a voltage of 1.46 V at 10 mA cm−2. Experimental analysis reveals that, during OER, Fe dissolution into electrolyte occurs for NiFe LDH and NixFe1−xP, which were both converted into NiOOH, well explaining their similar activity. Interestingly, Fe dissolution is significantly mitigated in NixFe1−xS, forming partially oxidized Fe2O3/FeOOH species. Theoretical calculations confirmed that Fe2O3/FeOOH is responsible for the enhanced OER energetics of NixFe1−xS. These observations provide new insights on the distinct activity of NiFe-based electrocatalysts, guiding their rational design as well.

NiCuCoS3 chalcogenide as an efficient electrocatalyst for hydrogen and oxygen evolution

Herein, a newly developed non-noble metal water splitting catalyst based on NiCuCoS3 was reported. Water splitting catalysts are largely developed with noble-based transition metals to lower the energy requirement for the overall water splitting reactions. However, the high cost of precious metal-based catalyst necessitated ongoing search for cheap and efficient oxygen and hydrogen evolution reaction catalysts. NiCuCoS3 were prepared by solventless solid state method and was well characterized by several techniques including field emission scanning electron microscopy (FESEM), X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), Fourier Transform infrared red spectroscopy (FTIR), energy dispersive X-ray spectroscopy (XEDS). The as-prepared NiCuCoS3 was applied for water splitting activities with satisfactory performance. The onset for the oxygen evolution reaction (OER) in 1 M KOH was noticed at the electrode potential E = 1.78 V/RHE (vs. the reversible hydrogen electrode corresponding to an overpotential η = 0.55 V, with a current density of 10 mA cm−2 obtained at E = 1.92 V/RHE (η = 0.69 V). Similarly, the hydrogen evolution reaction (HER) occurred at an onset of E = −0.58 V/RHE, with a current density of 10 mA/cm2 obtained at E = 0.60 V/RHE (with η equal to E vs. RHE for the HER). Likewise, OER and HER had Tafel slopes (130 mV/dec and −116 mV/dec respectively). The developed catalyst also showed high stability as established by linear sweep voltammetry, chronoamperometry and chronopotentiometry. This approach is seen as the right track of making water electrolysis for hydrogen energy feasible through provision of low-energy requirement for electrolytic process.

Co/CoP Heterojunction on Hierarchically Ordered Porous Carbon as a Highly Efficient Electrocatalyst for Hydrogen and Oxygen Evolution

AbstractDesigning non‐precious electrocatalysts to synergistically achieve a facilitated mass/electron transfer and exposure of abundant active sites is highly desired but remains a significant challenge. Herein, a composite electrocatalyst consisting of highly dispersed Co/CoP heterojunction embedded within a hierarchically ordered macroporous‐mesoporous‐microporous carbon matrix (Co/CoP@HOMC) is rationally designed through the pyrolysis of polystyrene sphere‐templated zeolite imidazolate framework‐67 (ZIF‐67) assemblies. The combined experimental and theoretical calculations reveal that Co/CoP interfaces not only provide richly exposed active sites but also optimize hydrogen/water absorption free energy via electronic coupling, while the interconnected macroporous structure enables a superior mass transfer to all accessible active sites. As a result, the as‐developed Co/CoP@HOMC composites exhibit outstanding catalytic activity with overpotentials of only 120 and 260 mV at 10 mA cm−2 for the hydrogen evolution reaction and oxygen evolution reaction in 1.0 m KOH, respectively. Moreover, an alkaline electrolyzer constructed by Co/CoP@HOMC requires an ultralow cell voltage of 1.54 V to achieve 10 mA cm−2, outperforming that of the Pt@C||IrO2@C couple (1.64 V).

Electrodeposited Cobalt Stannide: A Highly Efficient Oxygen Evolution Reaction Catalyst

The oxygen evolution reaction is the most kinetically hindered process in water electrolysis. Thus, oxygen evolution catalysts are required to improve the reaction kinetics. Precious metal catalysts are highly active, but the raw materials are scarce and costly. Thus, catalysts based on earth-abundant elements have drawn attention, and high performance, low-cost, and practial catalysts have been reported. Of the precious-metal-free commercial electrocatalysts, cobalt oxides are among the most important, and their catalytic properties can be improved by incorporating other elements. In this paper, we report that electrodeposited cobalt stannide (CoSn2) is a highly efficient oxygen evolution electrocatalyst, showing long-term electrochemical stability under alkaline conditions. Under optimal conditions, the catalyst operates at overpotentials of 250 and 300 mV at current densities of 1 and 10 mA cm−2, respectively, and has a Tafel slope of 64 mV dec−1. Furthermore, the prepared CoSn2 shows good electrochemical stability, and the overpotential for catalytic current densities of 1 and 10 mA cm−2 remained stable during electrolysis for 110 h. The results indicate that the as-prepared CoSn2 shows oxygen evolution reaction activity comparable to P- and Se-containing cobalt-based benchmark catalysts and suggest that electrodeposited CoSn2 is an attractive noble-metal-free catalyst for water oxidation.

Direct One-Step Growth of Bimetallic Ni2Mo3N on Ni Foam as an Efficient Oxygen Evolution Electrocatalyst.

A simple and economical synthetic route for direct one-step growth of bimetallic Ni2Mo3N nanoparticles on Ni foam substrate (Ni2Mo3N/NF) and its catalytic performance during an oxygen evolution reaction (OER) are reported. The Ni2Mo3N/NF catalyst was obtained by annealing a mixture of a Mo precursor, Ni foam, and urea at 600 °C under N2 flow using one-pot synthesis. Moreover, the Ni2Mo3N/NF exhibited high OER activity with low overpotential values (336.38 mV at 50 mA cm−2 and 392.49 mV at 100 mA cm−2) and good stability for 5 h in Fe-purified alkaline electrolyte. The Ni2Mo3N nanoparticle surfaces converted into amorphous surface oxide species during the OER, which might be attributed to the OER activity.

Endohedral Fe3C decorated multi-walled CNTs as an efficient electrocatalyst for oxygen evolution

The design and fabrication of high-performance and low-cost electrocatalysts for the oxygen evolution reaction (OER) are highly desirable towards the next-generation energy storage and conversion technologies. Carbon nanotubes (CNTs), the typical non-precious metal-based catalyst, have drawn significant attentions in electrochemical OER, whereas their low catalytic performance and cumbersome synthesis route seriously prohibit the scalable applications in OER. In this study, a facile and economical strategy (namely, the simple one-step pyrolysis of Fe(C5H5)2) was dedicatedly exploited for successfully producing CNTs encapsulated with Fe3C nanoparticles (NPs). It is found that encapsulated Fe3C NPs significantly enhance the alkaline OER activity and the stability of CNTs. Our experimental investigations indicate the active sites of this Fe3C@CNTs electrocatalyst for OER are the oxygen-containing functional groups bonding to the surface of CNTs. The interaction between Fe3C NPs and CNTs boosts the OER activity and the stability of CNTs. In sum, the simple and low-cost synthetic strategy of Fe3C@CNTs combined with its excellent catalytic performances prompts it promising for future practical OER.

Defect-Rich Fe-Doped CoP Nanosheets as Efficient Oxygen Evolution Electrocatalysts

Defect-Rich Fe-Doped CoP Nanosheets as Efficient Oxygen Evolution Electrocatalysts

Co0.85Se nanoparticles armored by N-doped carbon layer with electronic structure regulation functions: An efficient oxygen evolution electrocatalyst

In this work, with the assistance of polymeric nonionic surfactant Pluronic F127, 2D nanosheets glycerol cobalt self-assembled into the ball-flower structure composites (CoG@F127). Then, CoG@F127 is coated by polydopamine (PDA) to form CoG@F127@PDA. After the calcination with Se powder, CoG@F127@PDA is transformed into the ball-flower hierarchical structure Co0.85Se-NC/C, in which Co0.85Se nanoparticles are coated with nitrogen doped carbon (NC). The Co0.85Se nanoparticles anchored on the NC can avoid the aggregation, maintain structure stability and expose more electrocatalytic active sites for oxygen evolution reaction (OER). Specially, Co0.85Se-NC/C-750 shows a small Tafel slope of 47.2 mV dec-1 in 1.0 M KOH that is even lower than IrO2 and most of the reported Co-based catalysts. Besides, the theoretical calculations by density functional theory (DFT) suggest that NC could tailor the electronic structure of Co0.85Se, leading to optimized free energy change (ΔG) of the speed-controlled step and density of states (DOS).

Double doping of V and F on Co3O4 nanoneedles as efficient electrocatalyst for oxygen evolution

Rationally designing high-activity catalyst for oxygen evolution reaction (OER) is of primary importance due to its sluggish kinetic process in water splitting. Herein, we report a metallic (V) and nonmetallic (F) double doping in Co3O4 with nanoneedles structure, which is synthesized through facile oil bath and annealing. Electrochemical measurements show that the Co3O4 dopped with fluorine and vanadium (F0.2-V-Co3O4-350) only needs a low overpotential of 320 mV to afford a current density of 10 mA cm−2, which is superior to commercial RuO2. The excellent electrocatalytic performance can be attributed to double doping of vanadium and fluorine which have strong electron absorption effect to optimize the density of electrons in Co3O4. Besides, nanoneedles structure can enlarge exposure of active sites. And its great durability is evaluated through 2000 cycles CV test. Furthermore, the optimal ratio of fluorine to vanadium and different annealing temperatures of the target catalyst are explored reasonably.

Efficient Oxygen Evolution Electrocatalyst by Incorporation of Nickel into Nanoscale Dicobalt Boride

AbstractRecently, transition metal borides attracted increased attention as electrocatalysts for the oxygen evolution reaction. Here, we show how the incorporation of nickel into nanoscale dicobalt boride results in an improvement of the activity and stability of the catalyst in alkaline electrolytes. The borides are obtained by a one‐step solution synthesis, calcined, and characterized by X‐ray diffraction and scanning electron microscopy. For(Co1‐xNix)2B (x=0, 0.1, 0.2, 0.3, 0.4, and 0.5), (Co0.9Ni0.1)2B shows the best performance with an overpotential of η=371 mV at 10 mA cm−2 in 1 M KOH. Normalization to the electrochemical surface area shows a clear dependence on the activity with rising nickel content. X‐ray photoelectron spectroscopy reveals that the catalyst is modified under reaction conditions and indicates that CoOOH and Ni(OH)2 are formed as active surface species. Flame atomic absorption spectroscopy (F‐AAS) measurements show that no cobalt is dissolved during the electrochemical investigations, but the nickel concentration is increased on the surface of the catalyst as follows from XPS measurements after the electrochemical investigation.

Metal-Supported Perovskite as an Efficient Bifunctional Electrocatalyst for Oxygen Reduction and Evolution: Substrate Effect

Due to increased energy demand and environmental concerns, sustainable energy systems such as electrolyzers and Li-air batteries have attracted significant interest. However, it is imperative to develop an efficient inexpensive catalyst for the underlying reactions, namely oxygen reduction (ORR) and evolution (OER) reactions, to overcome their sluggish kinetics. In our previous work, a combination of silver and Co3O4 particles showed high bifunctional activity. Herein, we extend the study to investigate how the electrocatalytic activity is dependent on the oxide composition and the type of the underlaying substrate. A significant enhancement in OER performance is realized at perovskite-supported silver or gold electrodes with activity decreasing in the order Ag≥Au>GC. This is attributed mainly to a synergistic interaction between the oxide and metal support and the enhanced conductivity. The ORR activity observed at oxides loaded on Ag and Au bulk electrode is similar, however they exhibit about 450 mV lower overpotential than on GC. The improved activity at oxides/metal substrate renders this approach promising for O2-electrodes design.