Oxygen Evolution Catalysis Research Articles

NiCo-BDC derived Co3+ enriched NiCoxOy/NF nanosheets for oxygen evolution reaction

In recent years, transition metal catalysts due to their low price, excellent conductivity and high activity have been extensively studied in OER. It is worth noting that Co3+ plays a vital role in the process of oxygen evolution catalysis, because Co3+ ions are considered to be active sites. The development of catalysts with high Co3+ content has important application prospects for improving water oxidation efficiency. This paper uses a simple ligand-assisted synthesis method to promote the transformation of two-dimensional layered double hydroxides (LDHs) into two-dimensional metal organic frameworks (MOFs). MOF-OH/NF are quickly and easily prepared by electrooxidation, which exhibit superior OER properties, with a low overpotential of 260 mV and 420 mV for the oxygen evolution reaction (OER) at 100 mA cm−2 and 1000 mA cm−2. Moreover, the MOF-OH/NF has good stability in 1.0 M KOH electrolyte solution. This study provides a new idea for the design and synthesis of novel composite electrocatalysts.

α‐MnO2‐Sensitized SrCO3−Sr(OH)2 Supported on Two‐Dimensional Carbon Composites as Stable Electrode Material for Asymmetric Supercapacitor and Oxygen Evolution Catalysis

AbstractWe developed α‐MnO2‐sensitized SrCO3−Sr(OH)2 supported on amine functionalized reduced graphene oxide (rGO) nanosheets (denoted as MSSG) to understand the energy storage and the electrocatalytic properties. Three different nanocomposites with the tuned Mn precursors such as 0.625, 1.25 and 2.5 mmol, were prepared and denoted as MSSG‐1, MSSG‐2 and MSSG‐3, respectively and loaded on the electrode's surface. Among the nanocomposites loaded electrodes, MSSG‐1 loaded electrodes exhibit a maximum specific capacitance (Csp) of 792 F/g at 3.5 A/g current density and is morphologically stable even after 5000 cycles with a retention level of 95.9 %. With this outcome, the assembled asymmetric supercapacitor (AASC) device is mechanized effectively to power the light emitting diodes (LEDs) for 62 s continuously. In addition, the prepared electrode materials were examined for oxygen evolution reaction (OER) for enhanced electrocatalytic performance with low overpotential (346 mV at 10 mA cm−2 current density) and Tafel slope (97 mV Dec−1). In addition, the long‐term durability study represents a stable performance of the loaded electrode lasting up to 72 h. Notably, the mesoporous nanostructures at the electrode surface offer an effective synergistic effect between SrCO3−Sr(OH)2 supported on NH2‐functionalized rGO nanosheets (SSG) and α‐MnO2.

Effect of cobalt doping-regulated crystallinity in nickel-iron layered double hydroxide catalyzing oxygen evolution

The formation of a crystalline-amorphous (c-a) interface by modulating the crystallinity of the material is a promising strategy for oxygen evolution reaction (OER). Therefore, a similar element substitution approach is reported in this study to regulate the catalyst’s crystallinity. Adjustment of the cobalt content in NiFe layered double hydroxide (LDH) by the solvothermal method enables the control of c-a interfacial site of the material. In 1 M KOH, the as-obtained Co1.98-NiFe LDH exhibited a low overpotential of 236 mV to achieve 20 mA cm−2. It also showed excellent stability, operating steadily at high current densities for 96 h without significant degradation in 1 M KOH or alkaline artificial and natural seawater electrolytes. Therefore, the OER activity of the catalysts was improved while ensuring structural stability. We believe that this method will provide new insights and perspectives for the development of highly efficient and stable OER catalysts.

A tin‐incorporated multi‐phase perovskite nanocomposite for efficiently catalyzing oxygen evolution reaction

The rational design of effective and specific catalysts for oxygen evolution reaction (OER) is of vital importance for the implementation of electrochemical water oxidation as a sustainable route to produce hydrogen. Perovskite oxides have attracted considerable interests in view of the highly tunable structural, electronic, and catalytic properties associated with their compositions. Herein, an efficient Sn-incorporated nominal perovskite nanocomposite, SrCo0.7Sn0.3O3−δ (SCS), derived from a facile one-pot self-assembly process, is designed as an outstanding electrocatalyst to catalyze OER in alkaline conditions. Benefiting from the unique structure, increased active oxygen intermediates, and favorable electrical conductivity, the optimized SCS exhibits superior OER electrocatalytic performance, including low overpotential of only 309 mV at 10 mA cm−2, fast kinetics with a small Tafel slope of 56 mV dec−1, and 72-fold improvement in mass activity and 108-fold enhancement in specific activity relative to the pristine SrCoO3−δ catalyst. The SCS catalyst also demonstrates excellent OER durability with negligible potential fluctuation for 30 hours continuous operation. This work highlights a promising strategy to develop high-performance perovskite nanocomposites to perform efficient OER electrocatalysis.

Tuning the interfacial electronic transitions of bi-dimensional nanocomposites (pGO/ZnO) towards photocatalytic degradation and energy application.

The two-dimensional carbonaceous nanocomposites tend to have extreme capacitance and catalysis activity because of their surface tunability of oxygenated moieties aiding in photocatalytic degradation. Herewith, we performed microwave-assisted alkaline treatment of graphene oxide sheets to attain defective sites on the graphitic surface by altering microwave parameters. The synergism of zinc oxide (ZnO) on the graphitic surface impacts electronic transitions paving paths for vacant oxygen sites to promote photocatalytic degradation and catalytic activity. The photocatalytic efficiency of the synthesized material for the degradation of rhodamine B (RhB) because of its susceptibility in industrial effluents, and the degradation rate was estimated to be around 87.5% within a short span of 30min by utilizing UV irradiation. Concomitantly, the pGO/ZnO coated substrate exhibits a specific capacity of 561.7 mAh/g and incredible coulombic efficiency illustrating pseudocapacitive nature. Furthermore, on subjecting the composite modified electrode to oxygen evolution catalysis due to the vacant sites located at the lattice edges attributing to the d-d coulombic interaction within the local electron clouds possessing a low overpotential of 205mV with a Tafel slope of 84 mV/dec. This modest approach boosts an eco-friendly composite to develop photocatalytic degradability and bifunctional catalytic activity for futuristic necessity.

Preparation and electrocatalytic performance of N-doped hierarchical porous carbon loaded with Fe/Fe5C2 nanoparticles

The development of efficient non-precious-metal catalysts for oxygen reduction reaction (ORR) is greatly important for accelerating the commercial application of fuel cells. Herein, polystyrene (PS) nanospheres are used as templates for the growth of zeolitic imidazolate framework (ZIF) complex precursors with variable molar ratios of Fe3+ to Zn2+ in situ. Through carbonization at a high temperature, the hierarchical porous carbon (HPC) materials with different proportions (xFeyZn-HPC, x + y = 100) have been prepared. The typical product 5Fe95Zn-HPC is composed of nitrogen (N)-doped hierarchical porous carbon loaded with Fe/Fe5C2 nanoparticles obtained at optimal molar ratio. As an electrocatalyst, the 5Fe95Zn-HPC shows a positive onset potential of 0.92 V (vs. RHE), half-wave potential of 0.77 V (vs. RHE) and limiting current density of 5.60 mA cm−2 at 0.055 V (vs. RHE). The hydrogen peroxide yield is less than 4.2%, and the electron transfer numbers are between 3.91 and 3.99 at 0.055 V~1.055 V in the catalytic ORR, which indicate that the reaction is dominated by four-electron reduction. The 5Fe95Zn-HPC has higher stability and methyl alcohol resistance in alkaline and acidic solutions. The above results indicate the excellent catalytic ORR performance of the 5Fe95Zn-HPC, almost as the commercial Pt/C. Additionally, 5Fe95Zn-HPC has the capacity to catalyze oxygen evolution reaction (OER) and adsorb methylene blue pollutants. Therefore, this work provides a practical method to design the hierarchical porous carbon-based material with outstanding multi-functions.

Ultrafast Regenerating Spent LiCoO2 Lithium‐Ion Batteries into Bifunctional Electrodes for Rechargeable Zn‐Air Batteries

AbstractThe ever‐increasing use of lithium‐ion batteries (LIB) results in piles of spent batteries, which threats the environment and the supply chain of strategic metals. Developing sustainable recycling strategies for the cathode of spent LIB can bring about promising environmental and economic benefits. In this work, we present an ultrafast high temperature shock process for regenerating typical LiCoO2 (LCO) spent cathodes into the carbon layer/Co3O4 composite (C/CO). The nanosized Co3O4 provides large active sties exposure, while the graphitized carbon layer can potentially enhance the electronic conductivity towards oxygen evolution and oxygen reduction (OER and ORR) catalysis. Benefiting from the enhanced active sties exposure, electronic conductivity, and the synergistic effect between the two domains, the C/CO composite shows efficient bifunctional (OER and ORR) electrocatalytic properties. The OER overpotential (at 10 mA cm−2) and ORR on‐set potential reach 245 mV and 0.90 V, respectively. Moreover, the aqueous rechargeable Zn‐air batteries using C/CO composite as air cathodes display high specific capacity (698 mAh g−1), power density (131 mW cm−2), and as well as cycling stability. This work provides a waste to treasure way that is eco‐friendly, low‐cost, and ultrafast for regenerating the spent LIB for further applications in energy storage systems.

A simultaneous phosphorization and carbonization strategy to synthesize a defective Co2P/doped-CNTs composite for bifunctional oxygen electrocatalysis

Integration of heteroatom doped carbon material and metal phosphide is an ideal strategy for bifunctional oxygen reduction and evolution catalysis. In this work, heteroatoms doped carbon nanotubes, together with cobalt phosphide (Co2P/doped-CNTs) are prepared with a simultaneous phosphorization and carbonization strategy. It is revealed that the in-situ generated Co2P weakens the catalytic graphitization effect of metallic Co during the carbonization process, thus bringing about large numbers of defects, which is conducive to generating more pyridinic-N species in the carbon nanotube. As a result, the ORR-active pyridinic-N species and the OER-active Co2P are enriched in the carbon nanotube after the introduction of phosphorus, therefore providing dual active sites. The resultant Co2P/doped-CNTs catalyst shows outstanding ORR and OER performances, which are comparable to those of the commercial counterparts. The bifunctional activity makes Co2P/doped-CNTs an effective air–cathode catalyst for the rechargeable zinc-air batteries, showing a high power density and prominent cycling stability. This work abandons the traditional post-treatment phosphating method and realizes the integration of simplicity, safety and high efficiency.

Effects of cation vacancies at tetrahedral sites in cobalt spinel oxides on oxygen evolution catalysis

The dissolution of substituted Zn2+ ions in Co–Al spinel oxides leads to cation vacancies at the tetrahedral sites, promoting the adsorption process of OH− ions for charge compensation and enhancing the activity for oxygen evolution catalysis.

Catalytic oxygen evolution from hydrogen peroxide by trans-[Co(en)2Cl2]@InBTB metal-organic framework catalytic system.

The diethylammonium counter-cations of the [Et2NH2]3[In3(BTB)4] metal–organic framework (InBTB MOF, BTB = 1,3,5-benzenetribenzoate) with an anionic framework can be effectively exchanged with cationic trans-[Co(en)2Cl2]+ complex ions through a simple cation-exchange process. The heterogenized trans-[Co(en)2Cl2]+-encapsulated InBTB MOF (trans-[Co(en)2Cl2]@InBTB) catalytic system maintained the activity of the captured trans-[Co(en)2Cl2]+ complex ion for hydrogen peroxide decomposition in aqueous solution under mild reaction conditions. The captured trans-[Co(en)2Cl2]+ complex also exhibited trans–cis isomerization to produce either cis-[Co(en)2Cl2]@InBTB or cis-[Co(en)2(H2O)Cl]@InBTB based on IR spectroscopic investigation. The trans-[Co(en)2Cl2]@InBTB catalytic system showed high recyclability for oxygen evolution from hydrogen peroxide. The catalytic ability of trans-[Co(en)2Cl2]@InBTB was maintained up to seven times of recycling.

High-frequency ultrasonic pyrolysis of 200 nm ultrafine Fe-doped NiO hollow spheres for efficient oxygen evolution catalysis

High-frequency ultrasonic pyrolysis (3 MHz) was developed to prepare ultrafine Fe-doped NiO porous hollow spheres ∼200 nm. The material showed a low overpotential of 288 mV for a current density of 10 mA cm−2 as oxygen evolution reaction catalyst.

Dynamic coordination transformation of active sites in single-atom MoS2 catalysts for boosted oxygen evolution catalysis

Design and synthesis [TMO6] of a doped MoS2 (TMO6@MoS2, TM = Mn, Fe and Co) single-atom catalyst to achieve high OER catalytic activity through an unprecedented dynamic coordination transformation from [TMO6] to [TMO3].

Interfacial engineering of heterostructured Fe-Ni3S2/Ni(OH)2 nanosheets with tailored d-band center for enhanced oxygen evolution catalysis.

Hydrogen production by electrochemical water splitting suffers from high kinetic barriers in the anodic oxygen evolution reaction (OER), which limits the overall efficiency. Herein, we report a structural and electronic engineering strategy by integrating self-standing Fe-doped Ni3S2 (denoted by Fe-Ni3S2) nanosheet arrays with Ni(OH)2 subunits to form heterostructured Fe-Ni3S2/Ni(OH)2 on a Ni Foam substrate. The strong electronic interaction between the Fe-Ni3S2 and Ni(OH)2 constituents contributes abundant catalytic sites and ensures high electron transfer. Moreover, the combined experimental and theoretical study revealed that the coupling of Ni(OH)2 onto the Fe-Ni3S2 is favorable for lowering the activation energy of water oxidation for favorable OER kinetics and upshifting the Ni d-band center to facilitate the adsorption of O-containing intermediates. Consequently, the optimized Fe-Ni3S2/Ni(OH)2 hybrid catalyst exhibits excellent OER performance in alkaline electrolytes with an ultralow overpotential of 202 mV at 10 mA cm-2, a small Tafel slope of 50.6 mV dec-1, and long-term durability under high current density (0.25 A cm-2) for up to 60 h without significant deactivation. Moreover, a two-electrode Fe-Ni3S2/Ni(OH)2||Pt/C electrolyzer requires only a low voltage of 1.54 V at 10 mA cm-2 for overall water splitting. This study emphasizes the importance of interface and surface engineering in achieving highly efficient electrocatalysts.

Highly efficient oxygen evolution catalysis achieved by NiFe oxyhydroxide clusters anchored on carbon black

The NiFe-oxyhydroxide/C OER catalyst is prepared through the hydrolysis of nickel and iron salts in the presence of carbon black. It exhibits an overpotential of 269.6 mV at 10 mA cm−2 and a mass activity of 593.1 A g−1 at an overpotential of 320 mV.

Electrochemical deposition of amorphous cobalt oxides for oxygen evolution catalysis.

The oxygen evolution reaction (OER) is crucial in water splitting for hydrogen production. However, its high over-potential and sluggish kinetics cause an additional energy loss and hinder its practical application. The cobalt spinel oxide Co3O4 exhibits a high catalytic activity for the OER in alkaline solutions. However, the activity requires further enhancement to meet the industrial demand for hydrogen production. This paper presents an electrochemical deposition method to obtain cobalt oxides with a controllable crystallinity on carbon paper (CP). Usually, cobalt oxides grown on CP have a Co3O4 spinel oxide structure. The self-supported Co3O4/CP exhibited a considerable catalytic activity for the OER. When a VS2 layer grown on the CP beforehand by a hydrothermal method was used as substrate, the deposited cobalt oxides were in an amorphous state, denoted as CoOx/VS2/CP, which exhibited a higher OER activity and better stability than those of Co3O4/CP. The enhancement in the catalytic activity was attributed to the mixture formation of different types of cobalt species, including Co3O4, CoO, Co(OH)2, and metallic Co, because of the reduction by VS2. We also clarify the significance of the crystallinity of cobalt oxides in the improvement in the OER activity. This process can also be applied to the direct formation of other types of self-supported oxide electrodes for OER catalysis.

Fluidized Nanoparticles Catalyzed Oxygen Evolution Reaction: Enhanced Stability, Kinetics and Electrocatalytic Activity

Fluidized Nanoparticles Catalyzed Oxygen Evolution Reaction: Enhanced Stability, Kinetics and Electrocatalytic Activity

Glycine-nitrate derived cobalt-doped BiPO4: An efficient OER catalyst for alkaline electrochemical cells

The investigation of cost effective and earth abundant electro-catalyst to catalyze oxygen evolution reaction (OER) is highly desirable for the development of future sustainable energy. Herein, a facile one step glycine-nitrate decomposition method has been proposed to synthesize crystalline un-doped and cobalt doped BiPO4. The prepared un-doped and cobalt doped BiPO4 have been evaluated as potential electro-catalysts for OER. The XRD, XPS and ICP-OES results reveal that BiPO4 undergo surface reconstruction during OER and thereby converted into Bi2O3. Thus, the in situ formed Bi2O3 is the real active catalyst to catalyze OER where 5% cobalt doped BiPO4 exhibits excellent OER activity in terms of low overpotential of 328 mV and 394 mV to afford the current density of 10 and 50 mA cm−2 respectively, which is much lower than that of the un-doped BiPO4 (480 mV). Besides, the polarization curves of 5% cobalt doped BiPO4 shows negligible difference in overpotential even after 20 h of continuous electrolysis, demonstrating excellent stability in alkaline KOH. This work demonstrates intrinsic electro-catalytic activity of phosphate based electro-catalyst can be improved by doping with suitable transition metal and through surface reconstruction.

Porous carbon cubes decorated with cobalt nanoparticles for oxygen evolution catalysis in Zn‐air batteries

For commercialization of zinc-air batteries, it is important to replace expensive noble metal catalysts with inexpensive carbonaceous materials. Herein, an efficient oxygen evolution reaction (OER) catalyst composed of a unique porous tunnel carbon cube and cobalt nanoparticles ([email protected]) was fabricated to facilitate oxygen diffusion and create electron conduction networks. As an OER catalyst for zinc-air batteries (ZABs), the resulting [email protected] demonstrate enhanced OER activity, similar to that of the benchmark RuO2. In OER performance, [email protected] exhibits the excellent mass activity of 49.9 mA mg−1 at overpotential (η) of 0.47 V and the high current density of 91.5 mA cm−2 at 1.75 V (vs RHE), compared to commercial RuO2 catalysts. The use of [email protected] as the OER catalyst for ZAB maintains stable charge overpotential with as little as 0.05 V variation during 250 cycles, which extends the stable discharge-charge cycle performance compared to RuO2. This work highlights a facile approach to fabricate OER catalysts without noble metals for enabling stable charge state and long life ZABs.

3D Urchin-like Hierarchical Black TiO2 Hollow Nanospheres: A Highly Active and Stable Electrocatalyst for Water Oxidation in Alkaline and Neutral Media

Highly proficient, earth-abundant, long-term stable bifunctional electrocatalysts are very much desired for overall water splitting reactions. The present paper describes one such stable bifunctional electrocatalyst, 3D hollow nanostructured hierarchical hydrogenated TiO2 (H-TiO2) prepared by low-temperature treatment. The H-TiO2 electrocatalyst can catalyze oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) with a low overpotential of 270 and 128 mV at 10 mA cm–2 in alkaline media. Moreover, it exhibits an unusual catalytic activity in neutral electrolyte as well. The corresponding lower Tafel values indicate faster reaction kinetics on the H-TiO2 surfaces. When H-TiO2 is implemented as both the anode and cathode in a two-electrode system for overall water splitting in alkaline and neutral media, it only needs 1.57 and 2.11 V to reach a current density of 10 mA cm–2 and displays good durability for 12 h. The results suggest that Ti3+ and abundant oxygen vacancies in H-TiO2 favor HER and OER, which might originate from the enhanced electrical conductivity and rapid charge transfer rate due to the controlled interplay of the favoring factors. Thus, the present research work demonstrates a promising strategy for developing a highly efficient, stable, and carbon-free substitute for noble metal-based electrocatalysts for the overall water splitting in alkaline and neutral media.

Tailoring manganese oxide nanoplates enhances oxygen evolution catalysis in acid

Achieving active and stable oxygen evolution reaction (OER) in acid media is highly promising towards cost-effective and sustainable proton exchange membrane (PEM) electrolyzers, especially driven by the two-dimensional (2D) nanostructured catalysts. Here, we report a single-phase manganese tetroxide nanoplates (R20-Mn) by simply rapid annealing of manganese chloride tetrahydrate in air as an efficient and durable electrocatalyst for acidic OER. Agreeing well with the theoretical calculations of significantly reduced overpotentials compared with commercial RuO2 catalyst, R20-Mn delivers an exceptionally intrinsic activity, achieving ultralow overpotentials of 210 mV at a current density of 10 mA cm−2 for OER under acidic media. Therefore, this work provides an important complement to design 2D single-phase transition metal oxides catalysts with prominent activity in acidic water electrolysis.