Oxygen Evolution Catalysts Research Articles

CdSe-Co3O4@TiO2 nanoflower-based photoelectrochemical platform probing visible light-driven virus detection.

The design and construction of a visible light-driven photoelectrochemical (PEC) device is describedbased on a CdSe-Co3O4@TiO2 nanoflower (NF). Moreover, an application to the ultrasensitive detection of viruses, such as hepatitis E virus (HEV), HEV-like particles (HEV-LPs), and SARS-CoV-2 spike protein in complicated lysate solution, is demonstrated. The photocurrent response output of a PEC device based on CdSe-Co3O4@TiO2 is enhanced compared with the individual components, TiO2 and CdSe-Co3O4. This can be attributed to the CdSe quantum dot (QD) sensitization effect and strong visible light absorption to improve overall system stability. A robust oxygen-evolving catalyst (Co3O4) coupled at the hole-trapping site (CdSe) extends the interfacial carrier lifetime, and the energy conversion efficiency was improved. The effective hybridization between the antibody and virus resulted in a linear relationship between the change in photocurrent density and the HEV-LP concentration ranging from 10fgmL-1 to 10ngmL-1, with a detection limit of 3.5fgmL-1. This CdSe-Co3O4@TiO2-based PEC device achieved considerable sensitivity, good specificity, and acceptable stability and demonstrated a significant ability to develop an upgraded device with affordable and portable biosensing capabilities.

Material Changes in Electrocatalysis: An In Situ/Operando Focus on the Dynamics of Cobalt‐Based Oxygen Reduction and Evolution Catalysts

AbstractThe shift towards cheaper, non‐platinum group metal electrocatalyst materials for clean energy technologies is coupled with challenges in maintaining long‐term performance. For practical purposes, electrocatalytic stability typically focuses on catalyst electrochemical performance over time. However, a deeper understanding of catalyst material property changes during operation is needed to enable material‐specific design strategies for long‐term stabilization. In the last several decades, improvements in material characterization techniques have made it possible to probe the composition, structure, and degradation products of catalysts in situ/operando. Herein we review the current understanding of in situ/operando material stability of Co‐based electrocatalysts for the oxygen evolution (OER) and reduction reactions (ORR) in acidic and alkaline environments. We focus on in situ/operando materials characterization of three categories of Co‐based OER/ORR catalysts: oxides and (oxy)hydroxides, mixed‐metal catalysts, and non‐oxide materials. This review aims to compile and compare the results from multiple studies and techniques to provide insight into the role that the starting material, pH, and applied potential have on the active surface and stability of Co‐based materials. We conclude by highlighting directions that have been underexplored with opportunities for continued research including improving in situ/operando characterization, methods to probe long‐term material changes, and the development of operando studies on full‐scale devices. Using Co‐based materials as a case study, this review shows the vital role that in situ/operando characterization must play in the future of improving electrocatalyst stability.

Preparation of 3D Fe-Co-Ni-OH/NiCoP electrode as a highly efficient electrocatalyst in the oxygen evolution reactions

Hydrogen production by water electrolysis is an established technology to develop green storing of solar energy. Designing non-precious metal catalysts with abundant active sites and long durability is a necessary requirement for the hydrogen production from electrolytic water. Herein, we successfully fabricated a novel, highly efficient and non-precious metal oxygen evolution nanocatalyst by dealloying and rapid corrosion method. The catalyst is based on a 3-dimensional NiCoP framework and the desired Fe-Co-Ni-OH material was grown in situ through rapid etching to form Fe-Co-Ni-OH/NiCoP composite electrode. Electrochemical tests showed that the composite exhibits excellent OER (oxygen evolution reaction) activity for the corrosion time of 1 min. At current densities higher than 180 mA/cm2, the OER performance was even comparable to the catalytic activity of the noble metal catalyst RuO2. After 1000 cycles of stability tests, it still shows excellent OER stability. These findings provide a new insight to develop novel and highly efficient oxygen evolution catalysts.

Assembly of Fe7S8 and Co9S8 nanosheets coupled with Cu(OH)2 nanorods as highly efficient oxygen evolution catalyst

Traditional fossil fuels can be replaced with hydrogen, and electrolysis of water is thought to be one of the most efficient ways to produce hydrogen that is also pollution-free. The oxygen evolution reaction (OER), which is thought to be the bottleneck of the entire water decomposition, is a result of the intricate electrochemical mechanism and the slow kinetic process. In this paper, Cu(OH)2 forerunners with nanorods structure were combined on copper froth by straightforward submersion technique. Then, in a standard three-electrode system Fe7S8 and Co9S8 nanosheets with 3D structures were assembled on Cu(OH)2 precursors by electrodeposition. At an alkaline environment of 1 M KOH, Cu(OH)2/CF requires an overpotential of only 235 mV when the current density reaches 10 mA cm−2, which is lower than that of other reported catalysts. In addition, Fe7S8–Co9S8@Cu(OH)2/CF also showed excellent OER performance after long-term stability test, because bimetallic synergism can adjust the electronic structure of the catalyst and optimize its electrical conductivity. A feasible method for the design of a highly efficient oxygen evolution catalyst based on copper foam is reported in this paper.

Anion engineering in LiCoO2 for highly efficient oxygen electrocatalysis and rechargeable Zn-air batteries

Rational design of bifunctional catalysts for oxygen evolution and reduction reaction (OER and ORR) is vital to the development of Zn-air batteries (ZABs). Herein, we propose a facile strategy of anion engineering to improve the bifunctionality of layered LiCoO2 (LCO) for ZABs. Partial substitution of fluorine for oxygen can not only induce the formation of oxygen vacancies but also modulate the electronic structure of Co, thereby accelerating oxygen electrocatalysis kinetics. The potential gap (ΔE) between the OER potential at 10 mA cm−2 and ORR potential at −3 mA cm−2 of LiCoO1.8F0.2 (LCOF0.2) catalyst (0.986 V) is significantly lower than that of pristine LCO catalyst (1.162 V), indicating a higher bifunctional activity. As an application, a peak power density of the ZABs using LCOF0.2 as the air electrode is 193 mW cm−2, which is 1.53-fold higher than that of the LCO-based ZABs. This study demonstrates the feasibility of F doping to improve the bifunctional electrocatalytic performance of LiCoO2.

Anion Exchange Membrane Water Electrolysis Based on Nickel Ferrite Catalysts

AbstractA nickel ferrite was prepared by a liquid‐phase method and used as an oxygen evolution catalyst in an anion exchange membrane electrolyser. A complete physicochemical characterization of the catalyst was performed through X‐ray diffraction (XRD), Transmission electron microscopy (TEM) and X‐ray photoelectron spectroscopy (XPS). Then, the nickel ferrite was deposited by spray coating technique onto a Fumasep® FAA3‐50 anion‐exchange membrane to realize a catalyst‐coated membrane (CCM), and tested in a 5 cm2 single cell setup in the so‐called zero‐gap configuration. At 60 °C and 2.2 V, a current density of 3 A/cm2 was reached, which is higher than that obtained with NiO and IrO2 commercial catalysts. Moreover, a chronoamperometric test of 120 h highlighted the good stability of the synthesized catalyst.

Phenyl‐Free Polynorbornenes for Potential Anion Exchange Ionomers for Fuel Cells and Electrolyzers

AbstractIonomers in the catalyst layer play a critical role in the performance of fuel cells and electrolyzers. Phenyl adsorption on hydrogen oxidation catalysts and electrochemical oxidation of phenyl moieties on oxygen evolution catalysts are detrimental to the alkaline devices’ performance. Here the adsorption energy of phenyl‐containing ionomers is compared to provide the rationale for implementing phenyl‐free ionomers. Density functional theory calculations indicated that the norbornane fragment has minimal adsorption energy on Pt(111) due to the absence of aromatic π electrons. A soluble quaternized polynorbornene ionomer is prepared by vinyl addition polymerization, and it exhibits high performance in both fuel cells and electrolyzers, proving the advantage of the phenyl‐free structure. This study establishes the phenyl adsorption energy‐electrode performance relationship, highlighting the importance of material interactions between the catalysts and ionomers.

Oxygen evolution catalyst containing CoNi nanoalloy and carbon nanotube maximized the electrochemical surface area and intrinsic activity

To improve green-energy technology involving metal–air batteries, developing an efficient electrocatalyst for the oxygen evolution reaction (OER) and unveiling the factors that influence OER performance are crucial. Herein, we pyrolyzed the zeolitic imidazole framework to synthesize an N-doped carbon-based catalyst with a carbon nanotube (CNT) and the bimetallic CoNi nanoalloy. In addition, we optimized the size of CoNi particles and the formation of CNTs by controlling the reduction temperature (CoNi–CNT/NC-x; x is the reduction temperature). CoNi–CNT/NC-900 had the smallest CoNi nanoalloy particles, and CNTs were formed in CoNi–CNT/NC-600, -700, and −800 but not in −900. This infers that the ultrasmall CoNi nanoalloy particles and the formation of CNTs on their surface may come down to increasing the OER activity. Accordingly, the CoNi–CNT/NC-800 catalyst exhibited the highest OER performance (Ej10 = 1.53 V). This study proposes the rational design of an optimized catalyst with simple reduction condition control.

Dual-doping Fe-Ni oxide for ultrahigh performance seawater oxidation by high-concentration electrolytes

Inhibiting the chlorine evolution reaction (CER) is of great significance for the design and development of oxygen evolution catalysts with high current density for seawater electrolysis. The KOH concentration plays a very important role in controlling the potential of chlorine evolution in seawater electrolysis. However, the effect of its concentration, especially the high one (for example, >1 M), on the OER activity of different catalysts has not been studied so far. Here, we found that the KOH concentration has different linear effects on the OER activity for different catalysts, and we first propose a novel concept named concentration activity coefficient (CAC) to express the linear relationship between the OER activity of the catalyst and the KOH concentration in seawater electrolysis. Based on CAC, we report a Co S-NiFe2O4 catalyst with ultrahigh oxygen evolution activity in the 3 M KOH + seawater. This is due to the strong electronic interaction between Co and S-NiFe2O4. At current densities of 500 mA cm−2 and 1000 mA cm−2, the overpotentials of Co S-NiFe2O4 are 270 mV, and 287 mV, respectively, which are much lower than those of the existing electrocatalysts. More promising, the new catalysts also showed a splendid Tafel slope of 18.8 mV dec−1 and a long catalytic lifetime in concentrated alkaline electrolyte. Our findings provide a better understanding of the correlation between the KOH concentration and the OER activity and open new avenues for design and development of electrocatalysts for the next generation of high OER activity in seawater electrolysis.

Advances in Spin Catalysts for Oxygen Evolution and Reduction Reactions.

Searching for high effective catalysts has been an endless effort to improve the efficiency of green energy harvesting and degradation of pollutants. In the past decades, tremendous strategies are explored to achieve high effective catalysts, and various theoretical understandings are proposed for the improved activity. As the catalytic reaction occurs at the surface or edge, the unsaturated ions may lead to the fluctuation of spin. Meanwhile, transition metals in catalysts have diverse spin states and may yield the spin effects. Therefore, the role of spin or magnetic moment should be carefully examined. In this review, the recent development of spin catalysts is discussed to give an insightful view on the origins for the improved catalytic activity. First, a brief introduction on the applications and advances in spin-related catalytic phenomena, is given, and then the fundamental principles of spin catalysts and magnetic fields-radical reactions are introduced in the second part. The spin-related catalytic performance reported in oxygen evolution/reduction reaction (OER/ORR) is systematically discussed in the third part, and general rules are summarized accordingly. Finally, the challenges and perspectives are given. This review may provide an insightful understanding of the microscopic mechanisms of catalytic phenomena and guide the design of spin-related catalysts.

Perovskite Catalysts for Oxygen Evolution and Reduction Reactions in Zinc-Air Batteries

The Zinc-air battery (ZAB) has become a hot research topic for nearly a decade due to its high energy densities. As an important category of catalysts for ZAB, perovskites have attracted extensive interests because of their environmentally friendly properties, cheapness, and excellent electrocatalytic performances. This review article discusses the mechanistic analyses regarding the progress of perovskites for ZAB. In addition, electrode manipulation methods of perovskites for battery device are also emphasized. Finally, perspectives are given on the limitations of the current perovskite catalysts for ZABs. We hope that this review will provide new clues for promoting perovskites as catalysts for many energy-storage and conversion applications in the future.

Solid phase synthesis Ni3N and N-CNT synergetic corn-like multifunctional electrocatalyst

Nickel nitride (Ni3N) based catalysts have been studied extensively as oxygen evolution and hydrogen evolution reaction (OER/HER) catalysts because of good stability in alkaline solution. However, relatively poor electrical conductivity of Ni3N seriously restricted electron transfer from the Ni3N nanoparticles surfaces to inner substrates for highly efficient water splitting. In this work, solid phase synthesis strategy is implemented to prepare Ni3N/N-CNT composite. Ni3N/N-CNT shows impressive onset potential (0.81 V) and half wave (0.70 V) in oxygen reduction reaction (ORR), respectively. The higher limiting diffusion current of Ni3N/N-CNT shows the faster ORR kinetics. Ni3N was anchored on N-CNT, which displayed an outstanding OER and HER performance. The low OER overpotential (0.40 V) indicated that the Ni3N nanoparticles on N-CNT has significant enhancement of the OER activity. Significantly, Ni3N/N-CNT displays an excellent HER activity with preferable current density and low overpotential of 259 mV at 10 mA cm−2. The excellent multifunctional catalytic property is due to the electronic interaction between Ni3N and N-CNT which is beneficial for the mass and electron transfer. The conclusion broadens our understanding for exploit multifunctional catalysts.

NiFe Layered Double Hydroxide Electrocatalyst Prepared via an Electrochemical Deposition Method for the Oxygen Evolution Reaction

Herein, we aimed to obtain NiFe layered double hydroxide (LDH) with a controlled phase and surface morphology as a highly active and stable oxygen evolution catalyst via the electrochemical deposition method, which was thermodynamically stable for the oxygen evolution reaction (OER) in an alkaline medium. The NiFe-LDH sample was analyzed by sophisticated instruments and tested as an electrocatalyst on Toray carbon (TC). The NiFe-LDH electrocatalyst showed an excellent performance with lower overpotential of 0.27 V at 35 mA cm−2 and higher density of 125 mA cm−2 for OER in the 1 M KOH electrolyte solution. Moreover, the prepared catalyst exhibited unpredictable long-time stability for 700 h. From our knowledge, NiFe-LDH is a robust highly stable electrocatalyst compared to the recent reports.

Carbon fiber supported Co/Co3O4-embedded N-doped carbon microparticles for efficient overall seawater splitting and oxygen reduction

Due to low cost and abundance, direct seawater splitting to produce hydrogen is an encouraging strategy to alleviate the consumption of fossil energy, while also avoiding freshwater stress. However, when natural seawater is utilized as the electrolyte, the catalysts on the cathode and anode of water splitting should not only have high activity to promote energy efficiency, but also have good stability and durability to resist the corrosion of chloride ions. Herein, a hierarchical carbon-based catalyst for hydrogen and oxygen evolution, ZIF-67/CF-1, was prepared by annealing a composite of ZIF-67 and carbon fiber (CF). It exhibits good electrocatalytic activity and stability for overall splitting in natural seawater and neutral PBS solution. Impressively, when an electrolyzer consisting of ZIF-67/CF-1||ZIF-67/CF-1 is applied to overall seawater splitting, the current density of 10 mA/cm2 is achieved with a drive voltage of 2.46 V, which is only 0.28 V higher than precious metal-based electrolyzer (Pt/C||IrO2). Meanwhile, ZIF-67/CF-1 shows outstanding catalytic ability for oxygen reduction (E1/2 = 0.84 V, Tafel slope = 66.9 mV/dec), also demonstrating its application potential in rechargeable batteries and fuel cells.

Removal and recycling of selenite anions by iron-doped cobalt-based metal organic frameworks for oxygen evolution reaction

As the main form exists in selenium-containing wastewater, selenite (SeO32-) is often produced by human activities and is exceedingly difficult to be removed from wastewater. In this study, five iron-doped (Fe-doped) cobalt-based metal organic frameworks (Co/Fe-MOF) with different metal ratios were prepared to remove SeO32- anions. The prepared Co/Fe-MOF were confirmed by characterization and their adsorption properties experiments. They have excellent SeO32- removal performance at pH of 3–8 with a maximum adsorption capacity of 283.11 mg g−1 of Co-MOF. After uptaking SeO32- by Co/Fe-MOF, the used Co/Fe-MOF (U-Co/Fe) contains CoSeO4 and Fe2(SeO4)3 and can be used as electrocatalytic oxygen evolution catalysts. Their oxygen/selenium vacancies can reduce the overpotential of the oxygen evolution reaction (OER). In 1.0 M KOH, U-Co0.90Fe0.10 displayed the lowest overpotential 326 mV at 10 mA cm−2. This study reveals the mechanism and resource upgrading process of SeO32- removal by Co/Fe-MOF and demonstrates that a small amount of Fe doping could improve the performance of OER.

IrPt Alloy Nanoparticles with Controllable Compositions as Catalysts for Electrochemical Oxygen and Hydrogen Evolution

When two metal precursors are reduced to form alloy nanoparticles (NPs), the final size usually varies by the composition because the reduction rate is different for each precursor. In this study, we report that the composition of IrPt alloy NPs can be easily controlled without affecting the size using an antisolvent crystallization-based method owing to the separation of the particle growth and precursor reduction steps. The synthesized IrPt alloy NPs displayed low overpotentials in both hydrogen evolution reaction (65 mV with a Tafel slope of 32.2 mV dec–1) and oxygen evolution reaction (240 mV with a Tafel slope of 77.9 mV dec–1) to deliver a current density of 10 mA cm–2 in H2SO4 (0.5 M), showing their enhanced electrocatalytic activities compared with the pure Pt and Ir catalysts.

Cobalt Sulfide Nanoparticles Encapsulated in Carbon Nanotube-Grafted Carbon Nanofibers as Catalysts for Oxygen Evolution

Cobalt Sulfide Nanoparticles Encapsulated in Carbon Nanotube-Grafted Carbon Nanofibers as Catalysts for Oxygen Evolution

Microscopic Bubble Accumulation: The Missing Factor in Evaluating Oxygen Evolution Catalyst Stability during Accelerated Stress Tests

Microscopic Bubble Accumulation: The Missing Factor in Evaluating Oxygen Evolution Catalyst Stability during Accelerated Stress Tests

Natural leaf-inspired solar water splitting system

We designed a monolithic artificial leaf that mimics a natural leaf; the artificial leaf has a crystalline silicon (c-Si) interdigitated back contact (collectively, c-Si IBC) structure. On the front-side of the artificial leaf, the c-Si module acts similar to chlorophyll in natural leaves, converting solar energy into photo-carriers. On the rear-side of the artificial leaf, a hydrogen and oxygen evolution catalyst converts the carriers into hydrogen; this occurs without blocking light, similar to the conversion of photo-carriers into chemical energy, which mostly occurs on the backside of natural leaves. The solar-to-hydrogen conversion efficiency of the c-Si IBC photoanode and artificial leaf was 10.1% and 8.4% respectively, which are higher than that of a natural leaf (0.1–1%).

Mixed Silver–Bismuth Oxides: A Robust Oxygen Evolution Catalyst Operating at Low pH and Elevated Temperatures

Mixed Silver–Bismuth Oxides: A Robust Oxygen Evolution Catalyst Operating at Low pH and Elevated Temperatures