Efficient Oxygen Evolution Electrocatalysts Research Articles

Single-Source-Precursor Derived Transition Metal Alloys Embedded in Nitrogen-Doped Porous Carbons as Efficient Oxygen Evolution Electrocatalysts.

Carbon supported metallic nanomaterials are of great interest due to their low-cost, high durability and promising functional performance. Herein, a highly active oxygen evolution reaction (OER) electrocatalyst comprised of defective carbon shell encapsulated metal (Fe, Co, Ni) nanoparticles and their alloys supported on in-situ formed N-doped graphene/carbon nanotube hybrid is synthesized from novel single-source-precursors (SSP). The precursors are synthesized by a facile one-pot reaction of tannic acid with polyethylenimine and different metal ions and subsequent pyrolysis of the SSP. Benefiting from the heteroatom doping of carbon and formation of well-encapsulated metal/alloy nanoparticles, the obtained FeNi@NC-900 catalyst possesses lowest overpotentials of 310 mV to achieve a current density of 10 mA cm-2 for OER with a small Tafel slope value of 45 mV dec-1 , indicating excellent catalytic performance due to the following features: (1) A synergistic electronic effect among metal alloy nanoparticles, nitrogen-doped carbon, and entangled carbon nanotubes; (2) penetration of electrolyte is promoted towards the active sites through the porous structure of the formed mesoporous carbon clusters; (3) the unique core-shell nanostructure of the hybrid material effectively curbs the degradation of electrocatalyst by protecting the alloy nanoparticles from harsh electrolyte. This work advances an inexpensive and facile method towards the development of transition metal-based hybrid material for potential energy storage and conversion.

Efficient bifunctional cerium-zeolite electrocatalysts for oxygen evolution and oxygen reduction reactions in alkaline media

Four cerium-zeolites were examined as low-cost bifunctional electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in an alkaline solution. Cerium-exchanged zeolites, synthetic 13X and natural clinoptilolite were employed as prepared and calcined (cal). Four samples (Ce-13X cal, Ce-13X, Ce-Cli cal, and Ce-Cli) were characterized by X-ray powder diffraction analysis (XRPD), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, fluorescence spectroscopy and Brunner-Emmet-Teller (BET) method. All four zeolites exhibited activity for the two studied reactions. Ce-13X cal gave the lowest onset potential accompanied by the highest OER current density. Furthermore, Ce-13X cal showed the most positive ORR onset potential value of 0.84 V and the most positive ORR half-wave potential of 0.75 V (ca. 50 mV more positive than value for the other three cerium-zeolite electrodes) accompanied by the lowest Tafel slope of 80 mV dec−1. Koutecky-Levich analysis indicated that ORR follows 2-electron pathway. Overall, Ce-13X cal showed the best OER/ORR performances in alkaline solution.

The influence of increased content of Ni(III) in NiFe LDH via Zn doping on electrochemical catalytic oxygen evolution reaction

Developing efficient oxygen evolution electrocatalysts always shows great importance in the field of electrolysis of water. In this work, Zn-doped NiFe LDH is synthesized via a facile hydrothermal reaction. A series of structural characterizations revealed that the doping of Zn into NiFe LDH lattice can cause lattice distortion, which facilitates the formation of active NiOOH layers. The Zn–NiFe LDH electrocatalyst shows excellent performance in electrocatalytic oxygen evolution reaction, even overbeat the state-of-art RuO2. In addition, the doping of Zn into NiFe LDH significantly enhances the electrocatalytic stability of NiFe LDH, with only a 32.7 mV increase in potential after 100 h continuous OER electrolysis in 1.0 M KOH. The Zn–NiFe LDH provides an ideal strategy for designing highly efficient OER electrocatalysts for real applications.

UCoO4/Co3O4 Heterojunction as a Low-Cost and Efficient Electrocatalyst for Oxygen Evolution.

The development of actinide materials has provided new strategies for the utilization of nuclear waste, such as depleted uranium, a mildly radioactive waste in the nuclear power industry, which could be a precious resource for many fields, especially water splitting. The catalytic performance of water splitting is limited by the slow kinetics of the oxygen evolution reaction (OER), and it is extremely challenging to design efficient OER catalysts that are highly stable and inexpensive. Here, we design and describe a series of U5-35%-Co3O4 electrocatalysts, which were synthesized using uranyl nitrate as a precursor via a simple and scalable method. Interestingly, when the U/Co molar ratio was 20%, a UCoO4/Co3O4 heterojunction formed with high catalytic efficiency and excellent long-term electrolytic stability. The UCoO4/Co3O4 heterojunction catalyst shows a lower overpotential (280 mV) at a current density of 10 mA cm-2, and the slope of Tafel is 43.8 mV decade-1 in a 0.1 M KOH alkaline solution. Soft X-ray absorption spectroscopy shows that the cooperative effect of UCoO4 and Co3O4 can improve the electrochemical activity of the material. This study produced an active U/Co-based catalyst for OER, which provides a simple, scalable, low-cost, and highly efficient catalyst for overall water splitting.

Porosification and Fe3+ Intercalation of Spent LiCoO2 as an Efficient Oxygen Evolution Electrocatalyst

Porosification and Fe³⁺ Intercalation of Spent LiCoO₂ as an Efficient Oxygen Evolution Electrocatalyst

MOF nanosheet array-derived NiS with Co, N-doped carbon layer: A highly efficient oxygen evolution electrocatalyst

The development of the hydrogen industry from electrolytic water is confined in great measure to the slow kinetics of oxygen evolution reaction (OER), which means the rational design of a stabilized and efficient OER electrode is the key. The construction of easily accessible hydroxide ion (OH−) adsorption sites can effectively accelerate the kinetics of the OER. Herein, the NiS/CoNC electrocatalysts, which can effectively adsorb OH− and exhibited excellent OER performance in an alkaline environment, were obtained by pyrolysis and sulfidation of NiCo-MOF nanosheets on nickel foam (NF). In particular, the optimized NiS/CoNC electrocatalyst achieved an overpotential of 46/106 mV at 10/100 mA cm−2 and Tafel slope of 57.41 mV dec−1, which is superior to most reported materials. The outstanding function of OER results from the NiOOH/CoOOH active component generated by surface reconstruction after activation of the NiS/CoNC catalyst and the excellent charge transfer capability of the NiS component. This work offers a scheme to construct the electrocatalysts derived from MOF with excellent OER performance.

Hollow urchin-like CoSe2 with high surface area as highly efficient electrocatalyst for oxygen evolution

• A novel hollow urchin-like CoSe 2 have been achieved using urchin-like Co(OH) 2 as template. • The annealed CoSe 2 with more active sites and ideal electronic structure can be used as highly efficient electrocatalyst for oxygen evolution. • This material only requires an overpotential value of 285 mV at the 10 mA·cm −2 current density. • This material shows excellent stability. CoSe 2 is considered as a terrific replacement for the noble metal oxides to accelerate the oxygen evolution reaction (OER). Herein, we develop a novel hollow urchin-like CoSe 2 using urchin-like Co(OH) 2 as template. The as-prepared CoSe 2 was treated at 300 °C. It displays low overpotential of 285 mV at the 10 mA·cm −2 current density, which is much lower than that of the treated flake CoSe 2 and untreated hollow urchin-like CoSe 2 . The cyclic voltammetry (CV) curves clearly demonstrated that the lager electrochemical active surface area of the CoSe 2 is attribute to the hollow urchin-like structure and the increase of the active site by heat treatment. Moreover, the heat treatment increases the number of antibonding orbitals of Co-Se, which is close to the ideal filling for OER. Therefore, the synergistic effect of the increased electrochemical active surface area and optimized electronic configuration enhances electrocatalytic activity of the catalyst. These results demonstrate the potential of hollow urchin-like CoSe 2 in the field of energy conversion and storage technologies, and open up a novel avenue to design of high surface area catalysts with excellent performance and durability as alternatives to the noble metal oxides.

Tuning the electronic structure of a metal–organic framework for an efficient oxygen evolution reaction by introducing minor atomically dispersed ruthenium

AbstractThe establishment of efficient oxygen evolution electrocatalysts is of great value but also challenging. Herein, a durable metal–organic framework (MOF) with minor atomically dispersed ruthenium and an optimized electronic structure is constructed as an efficient electrocatalyst. Significantly, the obtained NiRu0.08‐MOF with doping Ru only needs an overpotential of 187 mV at 10 mA cm−2 with a Tafel slop of 40 mV dec−1 in 0.1 M KOH for the oxygen evolution reaction, and can work continuously for more than 300 h. Ultrahigh Ru mass activity is achieved, reaching 56.7 A g−1Ru at an overpotential of 200 mV, which is 36 times higher than that of commercial RuO2. X‐ray adsorption spectroscopy and density function theory calculations reveal that atomically dispersed ruthenium on metal sites in MOFs is expected to optimize the electronic structure of nickel sites, thus improving the conductivity of the catalyst and optimizing the adsorption energy of intermediates, resulting in significant optimization of electrocatalytic performance. This study could provide a new avenue for the design of efficient and stable MOF electrocatalysts.

Tuning Electronic Structure and Composition of FeNi Nanoalloys for Enhanced Oxygen Evolution Electrocatalysis via a General Synthesis Strategy

Developing low-cost and efficient oxygen evolution electrocatalysts is key to decarbonization. A facile, surfactant-free, and gram-level biomass-assisted fast heating and cooling synthesis method is reported for synthesizing a series of carbon-encapsulated dense and uniform FeNi nanoalloys with a single-phase face-centered-cubic solid-solution crystalline structure and an average particle size of sub-5nm. This method also enables precise control of both size and composition. Electrochemical measurements show that among Fex Ni(1- x ) nanoalloys, Fe0.5 Ni0.5 has the best performance. Density functional theory calculations support the experimental findings and reveal that the optimally positioned d-band center of O-covered Fe0.5 Ni0.5 renders a half-filled antibonding state, resulting in moderate binding energies of key reaction intermediates. By increasing the total metal content from 25 to 60 wt%, the 60% Fe0.5 Ni0.5 /40% C shows an extraordinarily low overpotential of 219mV at 10 mA cm-2 with a small Tafel slope of 23.2 mV dec-1 for the oxygen evolution reaction, which are much lower than most other FeNi-based electrocatalysts and even the state-of-the-art RuO2 . It also shows robust durability in an alkaline environment for at least 50h. The gram-level fast heating and cooling synthesis method is extendable to a wide range of binary, ternary, quaternary nanoalloys, as well as quinary and denary high-entropy-alloy nanoparticles.

Application of Co/Co9S8@N, S doped porous carbon composites prepared by ball milling for zinc-air battery

• Metal sulfides were prepared by a unique strategy to achieve sulfidation and double doping with ammonium bisulfate. • The amount of ammonium bisulfate has a great effect on the synthesis of Co/Co 9 S 8 @N, S-PC. • Co/Co 9 S 8 @N, S-PC-N exhibits a unique porous morphology and optimized structure and composition. • Co/Co 9 S 8 @N, S-PC-N possesses outstanding exhibits the performance of double-effect oxygen catalysis. With the advantage of high electrocatalytic activity, cobalt sulfides has become an efficient electrocatalyst for oxygen evolution and oxygen reduction reaction (OER/ORR). Selecting an appropriate strategy to construct a optimal structure for cobalt sulfides to explore the potential of their application in zinc-air battery is one of the meaningful topics. Here we propose a facile strategy to synthesize Co/Co 9 S 8 @N, S doped porous carbon composite material with mesoporous structure by ball milling. The Co/Co 9 S 8 @N, S doped porous carbon composite material exhibits excellent dual function catalytic activity for OER and ORR. Also, the material exhibits excellent power density and cycle stability when applied to the electrode catalytic material of normal zinc-air battery. Among them, the optimal sample present better power density than Pt-Ru-C mixed catalyst used in the normal zinc-air battery, and the limit value is 202.5 mW cm -2 . Connecting two solid-state zinc-air batteries in series can meet the normal operation of 53 LED light-emitting diodes. This work can provide a powerful reference for the further development of cobalt sulfides in oxygen electrocatalysis and zinc-air battery.

Doping vacancy synergy engineering: Ce-doped FeNi-Sx micro-succulent ameliorating electrocatalytic oxygen evolution performance

The co-control strategy of doping and vacancy has proved to be an effective and flexible approach in the development of efficient catalysts because of the synergistic regulation of electronic structure and active site number. Here, we synthesized an electrocatalyst with a special micromorphology of succulent plants. In addition, the doping of the rare earth element Ce with a large ionic radius in NiFe bimetallic sulfides is accompanied by a large number of vacancies. Ion doping synergistic with vacancy engineering improves the electrochemical intrinsic performance in the OER process and has enhanced electron transfer ability and electrochemical specific surface area, thus exhibiting high electrocatalytic OER performance, small Tafel slopes, ultralow overpotential of 294 mV at 100 mA cm−2 and 276 mV at 50 mA cm−2 and robust operating durability. Combined with DFT calculations, the role of Ce ions in the NiFe bimetallic sulfide system was revealed. This work not only provides a strategy for designing ion doping to enhance vacancy concentration but also constructs an efficient and stable oxygen evolution electrocatalyst system, which provides an alternative path for designing efficient electric and photocatalysts.

Novel FeNi-FeCo-C composite nanofibers: Highly efficient electrocatalysts for oxygen evolution from water splitting

The development of a facile strategy to fabricate inexpensive and efficient nonnoble metal-based alloys to replace their traditionally costly noble-metal counterparts for electrocatalytic water splitting holds great appeal. Here, we report novel FeNi-FeCo-C composite nanofibers (FeNi-FeCo-C CNFs), which was prepared simply by electrospinning a precursor solution containing Fe, Ni and Co nitrates together with polyacrylonitrile powders and subsequent thermal treatment. The optimal FeNi-FeCo-C CNFs prepared with 10 wt% polyacrylonitrile at a thermal treatment temperature of 800 °C show excellent electrocatalytic performance for oxygen evolution in a 1 mol·L−1 KOH aqueous solution with a relatively small overpotential of 262 mV at 10 mA cm−2, a low Tafel slope of 47.2 mV dec−1, and excellent cycling stability. The present strategy will provide new insight for the design and fabrication of electrocatalysts for water splitting.

DFT-assisted rational design of CoMxP/CC (M = Fe, Mn, and Ni) as efficient electrocatalyst for wide pH range hydrogen evolution and oxygen evolution

DFT-assisted rational design of CoMxP/CC (M = Fe, Mn, and Ni) as efficient electrocatalyst for wide pH range hydrogen evolution and oxygen evolution

Design of metal‐substituted tungsten diboride as an efficient bifunctional electrocatalyst for hydrogen and oxygen evolution

Design of metal‐substituted tungsten diboride as an efficient bifunctional electrocatalyst for hydrogen and oxygen evolution

Porous Ni3S2-Co9S8 Carbon Aerogels Derived from Carrageenan/NiCo-MOF Hydrogels as an Efficient Electrocatalyst for Oxygen Evolution in Rechargeable Zn-Air Batteries.

Herein, we fabricate N-doped porous Ni3S2-Co9S8/carbon aerogels (Ni3S2-Co9S8/NCAs) using carrageenan/NiCo-metal-organic framework (MOF) hydrogels as the precursor via the high-temperature carbonization route with excellent electrocatalytic properties for the oxygen evolution reaction (OER). The electrochemical measurements indicate that the Ni3S2-Co9S8/NCA as a quintessential electrocatalyst exhibits excellent OER performance, which has outperformed most transition metal sulfide (TMS) catalysts in alkaline environments, as attested with a lower overpotential of 337 mV at 10 mA cm-2 and a smaller Tafel slope of 77 mV dec-1. Meanwhile, a Zn-air battery based on Ni3S2-Co9S8/NCA + Pt/C achieves a large power density of up to 256 mW cm-2 (and 193 mW cm-2), small charge/discharge voltage gap, and good cycling stability, notably better than the conventional RuO2 + Pt/C-based Zn-air batteries. These excellent electrocatalytic properties are mainly attributed to the distinct hierarchical porous structure and interfacial synergy between the Ni3S2 and Co9S8 nanoparticle structure with rich defects, facilitating the mass transport and high graphitization degree beneficial for electron mobility. It is envisioned that the research provides a novel approach for the exploration of marine biomass as an electrocatalyst.

Synergistically boosting the elementary reactions over multiheterogeneous ordered macroporous Mo2C/NC‐Ru for highly efficient alkaline hydrogen evolution

AbstractSimultaneously enhancing the reaction kinetics, mass transport, and gas release during alkaline hydrogen evolution reaction (HER) is critical to minimizing the reaction polarization resistance, but remains a big challenge. Through rational design of a hierarchical multiheterogeneous three‐dimensionally (3D) ordered macroporous Mo2C‐embedded nitrogen‐doped carbon with ultrafine Ru nanoclusters anchored on its surface (OMS Mo2C/NC‐Ru), we realize both electronic and morphologic engineering of the catalyst to maximize the electrocatalysis performance. The formed Ru‐NC heterostructure shows regulative electronic states and optimized adsorption energy with the intermediate H*, and the Mo2C‐NC heterostructure accelerates the Volmer reaction due to the strong water dissociation ability as confirmed by theoretical calculations. Consequently, superior HER activity in alkaline solution with an extremely low overpotential of 15.5 mV at 10 mA cm−2 with the mass activity more than 17 times higher than that of the benchmark Pt/C, an ultrasmall Tafel slope of 22.7 mV dec−1, and excellent electrocatalytic durability were achieved, attributing to the enhanced mass transport and favorable gas release process endowed from the unique OMS Mo2C/NC‐Ru structure. By oxidizing OMS Mo2C/NC‐Ru into OMS MoO3‐RuO2 catalyst, it can also be applied as efficient oxygen evolution electrocatalyst, enabling the construction of a quasi‐symmetric electrolyzer for overall water splitting. Such a device's performance surpassed the state‐of‐the‐art Pt/C || RuO2 electrolyzer. This study provides instructive guidance for designing 3D‐ordered macroporous multicomponent catalysts for efficient catalytic applications.

Metal-Functionalized Hydrogels as Efficient Oxygen Evolution Electrocatalysts.

Conductive polymer hydrogels have large surface areas and electrical conductivities. Their properties can be further tailored by functionalizing them with metals and nonmetals. However, the potential applications of metal-functionalized hydrogels for electrocatalysis have rarely been investigated. In this work, we report the synthesis of transition-metal-functionalized polyaniline-phytic acid (PANI-PA) hydrogels that show efficient electrocatalytic activities for the oxygen evolution reaction (OER). Among the many transition metals studied, Fe is accommodated by the hydrogel the most due to the favorable affinity of the PA groups in the hydrogel for Fe. Meanwhile, those containing both Fe and Co are found to be the most effective electrocatalysts for OER. The most optimized such hydrogel, NF@Hgel-Fe0.3Co0.1, which is made using a solution that has a 3:1 ratio of Fe and Co, needs an overpotential of only 280 mV to catalyze OER in 1 M KOH solution with a current density of 10 mV cm-2. Furthermore, these metal-functionalized PANI-PA hydrogels can easily be loaded on the nickel foam or carbon cloth via a simple soak-and-dry method to generate free-standing electrodes. Overall, this work demonstrates a facile synthesis and fabrication of sustainable and efficient OER electrocatalysts and electrodes that are composed of easily processable hydrogels functionalized with earth-abundant transition metals.

Amorphous CoV Phosphate Nanosheets as Efficient Oxygen Evolution Electrocatalyst.

The oxygen evolution reaction (OER) is crucial for hydrogen production. However, OER with four-electron transfer requires electrocatalysts to speed up its sluggish kinetics in alkaline solutions. Herein, amorphous CoV phosphate (denoted as CoV-Pi) nanosheets synthesized by a straightforward one-step hydrothermal approach is reported, which provide a low overpotential of 320 mV at 10 mA cm-2 , a small Tafel slope down to 48.8 mV dec-1 and long-term durability over 80 h. The efficient activity is ascribed to the amorphous nanosheets structure, high electrochemically active surface area, enhanced surface wettability and the synergistic effect of the active metal atoms. This study significantly indicates that CoV-Pi is a promising alternative to replace expensive noble metal-based catalysts for electrochemical water splitting.

Lanthanum oxide rods as a novel and efficient bifunctional hydrogen and oxygen evolution electrocatalyst for overall water splitting

Novel and efficient catalytic materials with enhanced electrocatalytic properties are needed for hydrogen production from water through electrochemical water splitting. In this study, novel lanthanum oxide rods were prepared using a facile, soft chemical process. These lanthanum oxide rods were used for electrocatalytic hydrogen and oxygen evolution reactions. Electrochemical studies of the catalyst at 100 mA cm−2 indicated overpotentials of ∼340 and ∼405 mV for hydrogen and oxygen evolution reactions, respectively. In addition, the lanthanum oxide rods demonstrated good stability. Finally, lanthanum oxide rods were used as the cathode and anode to fabricate the electrolyzer in a two-electrode configuration. This electrolyzer required 1.6 V to drive 10 mA cm−2, and its performance did not change significantly during durability testing. To the best of our knowledge, this is the first study demonstrating the use of lanthanum oxide rods in electrocatalysis. The prepared lanthanum oxide rods have good electrocatalytic activity, and therefore, they are promising materials for the development of alkaline electrolyzers.

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.