Efficient Bifunctional Oxygen Electrocatalysts Research Articles

Rational design of ultrafine cobalt free electrospun nanofibers as efficient and durable binfunctional oxygen electrocatalysts for rechargeable zinc-air battery

Rational design of efficient and stable bifunctional oxygen electrocatalyst is of significant importance for research and progress of rechargeable zinc-air battery (ZAB). Herein, ultrafine cobalt free perovskite type oxide Sr2Fe1.5Mo0.5O6-δ nanofibers (SFM NF) and SFM nanoparticles (SFM NP) have been prepared via the electrospinning technique and combustion technique, respectively, and their electrochemical behaviors in the field of ZAB have been studied. Our study demonstrates that SFM NF catalyst has better bifunctional electrocatalytic activities and more durable charge–discharge cycling stability than SFM NP catalyst. When used as cathode catalysts for ZABs, SFM NF electrode exhibits a higher peak power density of 137 mW cm−2 than 107.9 mW cm−2 for SFM NP electrode. In addition, SFM NF electrode presents a lower galvanostatic charge–discharge voltage gap (ΔE) of 0.94 V than 1.13 V for SFM NP electrode when operated at 10 mA cm−2, which can be explained by the enhanced bifunctional electrocatalytic activities. More importantly, SFM NF electrode presents a significantly low ΔE degradation rate of 0.01 V/100 h during the 300-hour operation, indicating its excellent change-discharge stability. Our findings indicate that SFM NF catalyst is a greatly promising cathode candidate of efficient and durable rechargeable ZAB, and the electrospinning technique is an effective strategy to prepare efficient electrocatalysts for energy storage and conversion application.

NiMn-based metal-organic framework with optimized eg orbital occupancy as efficient bifunctional electrocatalyst for lithium-oxygen batteries

Rational design and synthesis of highly efficient bifunctional oxygen electrocatalysts is significant for rechargeable lithium-oxygen batteries (LOBs). In this work, a bimetal coupling strategy has been adopted to fabricate Ni/Mn bimetal-organic framework (Ni/Mn-MOF). The LOBs equipped with NiMn0.05-MOF electrocatalyst exhibit excellent performances with large specific capacity of 28,464 mAh/g and extraordinary stability of 524 cycles at 100 mA g−1. Combining with the experimental results and density functional theory (DFT) calculation, it is found that the doped Mn cations enable triggering the redistribution of 3d electron in Ni sites, adjusting eg orbital occupancy of Ni and strengthening the hybridization between Ni −3d and O −2p orbits due to the intense electron coupling between Ni and Mn ions, which greatly optimizes the inherent absorption capability of NiMn0.05-MOF for LiO2 intermediate and thus decreases the energy barriers of oxygen redox reactions.

In-situ construction of Ruddlesden-Popper/perovskite heterointerface induces efficient bifunctional oxygen electrocatalyst for rechargeable zinc-air batteries

• Hierarchical RP-PSNC/P-PNC nanofibers with core-shell structure are synthesized. • RP-PSNC/P-PNC displays efficient bifunctional catalytic activities. • The interfacial vacancies and hierarchical structure increase the catalytic activities. • RP-PSNC/P-PNC-based batteries exhibit excellent power density and durability. Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are the prerequisite reactions in rechargeable zinc-air batteries (ZABs), but their kinetics are usually slow. In order to develop energy-efficient ZABs, it is highly desirable to pursue bifunctional catalysts with the accelerated reaction kinetics and the reduced overpotentials. Transition metal oxides are expected as promising alternatives to replace noble metal-based catalysts, but their catalytic activities are still far from desirable. Herein, we propose a modified layer of Ruddlesden-Popper perovskite (Pr,Sr) 2 Ni 0.5 Co 0.5 O 4-δ (RP-PSNC) on the perovskite PrNi 0.5 Co 0.5 O 3-δ (P-PNC) nanofiber by a simple impregnation method, receiving a (Pr,Sr) 2 Ni 0.5 Co 0.5 O 4-δ / PrNi 0.5 Co 0.5 O 3-δ (RP-PSNC/P-PNC) heterostructured nanofibers. The RP-PSNC/P-PNC hybrid catalyst exhibits a small overpotential and an excellent stability due to the large number of vacancies in the two-phase interface. The RP-PSNC/P-PNC-based liquid rechargeable ZAB reaches a power density of 145 mW cm −2 , and 230 h of long-term cycle performance. When assembled into flexible ZABs, it can also reach a power density of 51 mW cm −2 and a stable open circuit voltage (∼1.35 V) for 44 h. These results indicate that the bifunctional electrocatalyst of heterostructured RP-PSNC/P-PNC provides a new path for the modification of perovskites through multi-phase catalysts system, and has great potential in rechargeable ZABs and other energy conversion devices.

Calculation screening of Janus WSSe monolayer modified with single platinum group metal atom as efficient bifunctional oxygen electrocatalysts

Developing cost-effective bifunctional electrocatalysts is eagerly desirable for electrochemical energy applications. Herein, using the first-principles computations, the structural, electronic, magnetic, oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic properties of single platinum group metal (PGM) atom modified Janus WSSe monolayer systems are comprehensively investigated. The results reveal that the single PGM atom can be stably supported on the W top position of S side and effectively regulate the structural and electronic characteristics of Janus WSSe monolayer. Pd- and Pt-WSSe are effectively screened from the PGM-WSSe systems with the outstanding bifunctional catalytic activity elucidated, especially the Pd-WSSe exhibits even smaller overpotentials (ηORR ≈ 0.39 and ηOER ≈ 0.49 V). The mechanisms of prominent bifunctional catalytic activity of Pd- and Pt-WSSe are summarized including their moderate binding strength with O2 molecule, superior electrical conductivity, high intrinsic electric field and the d orbital occupancy of Pd and Pt atoms. Thus, the effective strategy to reduce the dosage of PGMs in PGM single atom catalysts (SACs) and to boost the bifunctional catalytic performance of Janus WSSe monolayer could be achieved, which would be useful to promote the exploration of novel bifunctional electrocatalysts.

Metal organic framework derived perovskite/spinel heterojunction as efficient bifunctional oxygen electrocatalyst for rechargeable and flexible Zn-air batteries

Interface engineering strategy has been developed to design efficient catalysts for boosting electrocatalytic performance in past few decades. Herein, heterojunctions of PrCoO3/Co3O4 nanocages (PCO/Co3O4 NCs) with atomic-level engineered interfaces and rich oxygen vacancies are proposed for Zn-air batteries. The synthesized product shows exceptional bifunctional activity and robust stability towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The enhanced catalytic capacity is primary attributed to the synergistic effect of PCO/Co3O4, evidenced by the experimental results and theoretical calculations. More importantly, the PCO/Co3O4 NCs assembled liquid Zn-air battery exhibits a power density of 182 mW cm−2 and a long-term operation of 185 h. When assembled into solid-state cable type battery, this newly designed catalyst also reaches a stable open circuit voltage (1.359 V) and a peak power density of 85 mW cm−3. Our findings provide essential guidelines of engineering heterostructured electrocatalysts for future wearable electronic devices.

CoS2/N,S co-doped mesoporous carbon with 3D micro-nano crosslinked structure as efficient bifunctional oxygen electrocatalysts for zinc-air batteries

This work describes a bifunctional oxygen catalyst made of cobalt disulfide encapsulated in N,S co-doped mesoporous carbon with a novel three-dimensional micro-nano crosslinking structure. The proposed composite materials exhibit promising oxygen electrocatalytic activity and stability. The composite assembled rechargeable zinc-air battery can achieve a high power density of 208.9 mW/cm2, and can be stably cycled for more than 160 h. Additionally, the all-solid zinc-air battery assembled with the electrocatalyst also performs admirably. The micro-nano crosslinking and high porosity structure, as well as the large number of active sites generated by the synergy of N,S doping and the close interface between carbon matrix and CoS2, contribute to the composite's exceptional electrochemical performance. This study's rational strategy lays the path for the development of other high-performance bifunctional electrocatalysts.

Boosting Oxygen Electrocatalysis by Combining Iron Nanoparticles with Single Atoms

The development of high-performance non-noble metal-based oxygen electrocatalysts is crucial for the practical application of zinc–air batteries. Most of them suffer from low intrinsic activity and poor stability, failing to meet the needs of practical applications. Here, we report an efficient and durable bifunctional oxygen electrocatalyst of Fe@Fe-SAC composite (SAC stands for single atoms on carbon). A facile and ease-to-scale-up process synthesizes it. Fe single-atom and Fe nanoparticles are anchored on nitrogen-doped porous carbon, with the latter encapsulated by the graphitic shell. It exhibits appealing activity and durability in a basic electrolyte, requiring a half-wave potential of 0.805 V for oxygen reduction reaction (ORR) and an overpotential of only 348 mV to deliver a current density of 10 mA cm−2 for oxygen evolution reaction (OER). Both activities are comparable to the corresponding benchmarking electrocatalyst of Pt/C for ORR and IrO2 for OER. The superior activities are attributed to the strong electronic interaction between metal single-atom and nanoparticles. The favorable stability is ascribed to the physical encapsulation of carbon coatings on nanoparticles. This work presents a feasible scheme for designing and large-scale preparation of high-performance non-noble metal-based bifunctional oxygen electrocatalysts.

Carbon dots bridge NiO and Mn2O3 as highly efficient bifunctional oxygen electrocatalysts for rechargeable zinc-air batteries

The development of high-efficiency, low-cost and durable bifunctional oxygen electrocatalysts is of great significance for the large-scale application of rechargeable zinc-air batteries. Herein, the carbon dots bridging nickel oxide and manganese trioxide through the oxygen-containing group of carbon dots (NiO-Mn2O3-CDs) for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is proposed. The optimal NiO-Mn2O3-CDs yields remarkable electrocatalytic activity with low overpotential (298 mV) to derive the 10 mA·cm−2 for OER and a high half wave potential (0.84 V vs. RHE) for ORR. The outstanding performances are attributed to the CDs covalently bridging Ni and Mn atoms, which reprogram the electronic structure of active sites and enhance charge transfer. Consequently, the rechargeable zinc-air battery test with NiO-Mn2O3-CDs as the air cathode deliver the excellent performances, including a high open voltage (1.51 V), a maximum power density (287 mW∙cm−2 @ 0.35 A∙cm−2) and robust cycling life, outperforming the commercial Pt/C + IrO2. This work presents an efficient strategy to construct the highly active and stability bifunctional air cathodes for electrochemical energy devices.

Engineering iron-group bimetallic nanotubes as efficient bifunctional oxygen electrocatalysts for flexible Zn–air batteries

Air cathode performance is essential for rechargeable zinc–air batteries (ZABs). In this study, we develop a self-templated synthesis technique for fabricating bimetallic alloys (FeNi3), bimetallic nitrides (FeNi3N) and heterostructured FeNi3/FeNi3N hollow nanotubes. Owing to its structural and compositional advantages, FeNi3/FeNi3N exhibits remarkable bifunctional oxygen electrocatalytic performance with an extremely small potential gap of 0.68 ​V between the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Theoretical calculations reveal reduced Gibbs free energy for the rate-limiting O–O bond formation during OER due to the self-adaptive surface reconfiguration, which induces a synergistic effect between Fe(Ni)OOH developed in situ on the surface and the inner FeNi3/FeNi3N. ZAB fabricated using the FeNi3/FeNi3N catalyst shows high power density, small charge/discharge voltage gap and excellent cycling stability. In addition to its excellent battery performance, the corresponding quasi-solid-state ZAB shows robust flexibility and integrability. The synthesis method is extended to prepare a CoFe/CoFeN oxygen electrocatalyst, demonstrating its applicability to other iron-group elements.

Bifunctional Catalytic Activity of Solvothermally Synthesized CeO2 Nanosphere/NiO Nanoflake Nanocomposites

The design and development of bifunctional electrocatalysts that can catalyze both the oxygen evolution reaction and oxygen reduction reaction (OER/ORR) is a burning issue for energy conversion and storage technologies. Herein, we demonstrate the bifunctional activity of CeO2 nanospheres embedded in NiO nanoflakes. The CeO2/NiO nanocomposites are synthesized solvothermally by varying their molar ratios. Among the synthesized nanocomposites, CeO2/NiO-2 exhibits an outstanding OER/ORR activity compared to those of individual counterparts and other compositions and outperforms the benchmark ORR catalyst Pt/C and the OER catalyst IrO2 in terms of stability. The CeO2/NiO-2 nanocomposite shows the low onset potential of 1.47 and 0.8 V (vs reversible hydrogen electrode) for OER and ORR, respectively. Moreover, a low potential difference (i.e., ΔE) of 0.86 V between the potential for 10 mA cm–2 OER current density and the ORR half-wave potential for CeO2/NiO-2 makes it an efficient bifunctional oxygen electrocatalyst. The excellent bifunctional activity of the nanocomposite is ascribed to the electronic synergy between CeO2 and NiO, which leads to the formation of an increased number of oxygen vacancy defects as well as more accessible active sites at an optimum molar ratio of CeO2 and NiO. The unique morphology of CeO2 nanospheres embedded in NiO nanoflakes facilitates the exposure of surface-active sites with the bifunctional nature of the catalyst. The practical applicability of the CeO2/NiO-2 nanocomposite is demonstrated with a Zn–air battery, which delivers 1.41 V open-circuit voltage and 105.0 mW cm–2 peak power density. It has long-term cycling stability for 22 h with negligible voltaic efficiency loss.

Salt-Templated Nanoarchitectonics of CoSe2-NC Nanosheets as an Efficient Bifunctional Oxygen Electrocatalyst for Water Splitting.

Recently, the extensive research of efficient bifunctional electrocatalysts (oxygen evolution reaction (OER) and hydrogen evolution reaction (HER)) on water splitting has drawn increasing attention. Herein, a salt-template strategy is prepared to synthesize nitrogen-doped carbon nanosheets encapsulated with dispersed CoSe2 nanoparticles (CoSe2-NC NSs), while the thickness of CoSe2-NC NSs is only about 3.6 nm. Profiting from the ultrathin morphology, large surface area, and promising electrical conductivity, the CoSe2-NC NSs exhibited excellent electrocatalytic of 10 mA·cm−2 current density at small overpotentials of 247 mV for OER and 75 mV for HER. Not only does the nitrogen-doped carbon matrix effectively avoid self-aggregation of CoSe2 nanoparticles, but it also prevents the corrosion of CoSe2 from electrolytes and shows favorable durability after long-term stability tests. Furthermore, an overall water-splitting system delivers a current density of 10 mA·cm−2 at a voltage of 1.54 V with resultants being both the cathode and anode catalyst in alkaline solutions. This work provides a new way to synthesize efficient and nonprecious bifunctional electrocatalysts for water splitting.

A Pyrolysis-Free Method Toward Large-Scale Synthesis of Ultra-Highly Efficient Bifunctional Oxygen Electrocatalyst for Zinc-Air Flow Batteries.

The transition-metal nitrogen-carbon (M-N-C) catalysts, as one of the optimal bifunctional oxygen catalysts, are vital for cathodic oxygen electrode of Zn-based air flow batteries (ZAFBs). However, chemical complexity of M-N-C catalysts prepared via the traditional pyrolytic process increases the difficulties of precise control toward configuration and repeatability, especially in large-scale synthesis. Herein, a bifunctional oxygen catalyst via a pyrolysis-free approach based on closed π-conjugated covalent organic polymers (COPs, microwave synthesis) is developed, which inherits the advantage of the well-defined configuration in an atomic manner. Profited from distinct catalytic centers and strong electronic coupling at the interface between COP and layered double hydroxides, the as-synthesized catalyst not only more easily permits large quantity production (>1kg per batch), but also maintains an ultrahigh bifunctional activity and a long cycle stability even after scale synthesis (ΔE [Ej10 - E1/2 ] = 591mV; energy efficiency drops by only 2.02% after 1200 cycles), which overwhelmingly exceeds the benchmark Pt/C+IrO2 and the state-of-the-art pyrolytic bifunctional M-N-C oxygen catalysts.

SnS2 Monolayer-Supported Transition Metal Atoms as Efficient Bifunctional Oxygen Electrocatalysts: A Theoretical Investigation

It is of significance to pursue eminent catalytic activity and nonprecious bifunctional electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), which is beneficial for renewable energy applications. Herein, the electrocatalytic performance of transition metal (TM) atoms supported on a SnS2 monolayer was investigated using first-principles methods based on density functional theory in the present work. Our results reveal that TM atoms supported on the surface of the SnS2 monolayer can effectively improve the catalytic performance of SnS2 for OER and ORR. Interestingly, the OER/ORR overpotentials of Ni/SnS2 and Pt/SnS2 are estimated to be 0.38/0.62 and 0.37/0.58 V, respectively, showing promising catalytic performance. Moreover, the volcano plots also evince that the efficient bifunctional electrocatalysts for OER/ORR are SnS2 monolayer-supported Ni or Pt atoms. This study will pave the way toward the synthesis of high-performance SnS2-based bifunctional oxygen electrocatalysts in future.

Ordered macroporous design of sacrificial Co/VN nano-heterojunction as bifunctional oxygen electrocatalyst for rechargeable zinc-air batteries

• •Ordered macroporous design of sacrificial Co/VN nano-heterojunction was developed. • •VN act as sacrificial OER promoter converting Co into active Co 3 O 4 /CoOOH species. • •The Co/VN electrode exhibits excellent performance in rechargeable zinc-air batteries. The development of efficient oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) bifunctional electrocatalysts is essential for rechargeable zinc-air batteries (ZABs). Herein, an ORR/OER bifunctional pre-catalyst consists of Co/VN heterojunction supported by N-doped carbon (NC) with three-dimensionally ordered macroporous (3DOM) architecture was fabricated. The VN was introduced as sacrificial promoter to facilitate the oxidization and self-reconstruction of Co into Co 3 O 4 and CoOOH during OER process, which acts as the real active OER component. On the other hand, the Co-decorated N-doped carbon is the active species for ORR reaction. Meanwhile, the 3DOM structure design also provides a large specific surface area and exposes rich active sites. Benefiting from those advantages, the Co/VN@NC exhibits good activity and stability towards ORR and OER reactions comparable with commercial catalysts. Moreover, density functional theory calculations confirmed that Co 3 O 4 and CoOOH exhibit higher adsorption energy for OH – and present an exothermic reaction in the OER process, which is beneficial to OER reaction. The ZABs using Co/VN@NC as bifunctional catalyst exhibits a high specific capacity of 775.68 mAh g −1 under 10 mA cm −2 and ultralong charge–discharge cycle life about 200 h at 20 mA cm −2 . This work provides a new strategy of using sacrificial heterojunction for the development of efficient and durable bifunctional oxygen electrocatalyst.

FePc nanoclusters modified NiCo layered double hydroxides in parallel with Ti3C2 MXene as a highly efficient and durable bifunctional oxygen electrocatalyst for zinc-air batteries

Boosting the bifunctional oxygen activity of layered double hydroxides (LDHs) is a frontier but challenging issue for metal-air batteries. Herein, an iron phthalocyanine (FePc) nanocluster modified NiCo LDH in parallel with Ti3C2 (FePc-NiCo-LDH/Ti3C2) two-dimensional multilayer structured bifunctional oxygen catalyst is engineered by growing NiCo-LDH in parallel with Ti3C2 followed with adsorbing FePc via electrostatic interaction approach. Thanks to the abundant retained Fe-Nx active sites, the FePc-NiCo-LDH/Ti3C2 catalyzes the oxygen reduction reaction (ORR) with a half-wave potential (E1/2) of 80 mV positive compared to Pt/C. Besides, the current density only drops 5% after 33,000 s of chronoamperometry test, confirming the robust ORR stability. On the other hand, there are electronic interactions formed between FePc nanocluster and NiCo-LDH/Ti3C2 which boosts the OER activity as demonstrated by the negatively shifted potential of 89 mV at 10 mA cm−2 versus RuO2. The overall ORR/OER activity makes FePc-NiCo-LDH/Ti3C2 ranking top among the most active analogous samples. The Zn-air battery (ZAB) assembled with FePc-NiCo-LDH/Ti3C2 as air electrode exhibits a peak power density of 148 mW cm−2 and can be charge-discharged continuously for 80 h. This direct engineering ORR/OER active center strategy offers a unique facile direction for the fabrication of oxygen electrode catalysts for renewable clean energy devices.

A dual metal-organic framework strategy for synthesis of FeCo@NC bifunctional oxygen catalysts for clean energy application

Developing high efficient bifunctional oxygen electrocatalysts for clean energy applications like Zin-air battery (ZAB) is highly desired, because it would reduce the cost and speed up the practical application of ZAB. Here we use a dual metal–organic framework (MOF) synthesis strategy to prepare the N-doped carbon supported bimetallic FeCo nanoparticle catalysts (marked as [email protected]) by pyrolysis of ZnCo-ZIF/MIL-101(Fe) composite. The [email protected] exhibits remarkable electrocatalytic activity for ORR with half-wave potential of 0.89 V vs. the reversible hydrogen electrode (RHE) and robust durability for both ORR and OER (oxygen reduction reaction and oxygen evolution reaction), which is attributed to the generation of Fe0.26Co0.74 crystalline phase and mesopores due to the dual-MOF synthesis strategy. The rechargeable ZAB based on [email protected] air electrode shows a maximum energy density of 139.6mW·cm−2 and excellent cyclic stability over 130 h, significantly surpassing the Pt and Ir-based ZAB. The present work provides a useful dual-MOF synthesis strategy for preparing high-performance multifunctional catalysts for ORR, OER and hydrogen evolution reaction (HER).

Efficient Bifunctional Oxygen Electrocatalysts for Rechargeable Zinc–Air Battery: Fe3O4/N−C Nanoflowers Derived from Aromatic Polyamide

AbstractThe development of low‐cost, high‐activity bifunctional oxygen electrocatalysts for rechargeable zinc–air batteries is highly desired. Herein, N‐doped carbon nanoflower embedded Fe3O4 nanoparticles were prepared using a simple and scalable method. The obtained electrocatalyst exhibits excellent activity and stability toward both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), as well as a small potential gap of 0.72 V between the half‐wave potential of ORR and the onset potential of OER potential, which is superior to the most previously reported bifunctional ORR/OER catalysts. The corresponding zinc–air battery exhibits good charged/discharge cycle performance as well as excellent discharge property, with a power density of 136.8 mW cm−2 at 200 mA cm−2 outperforming commercial Pt/C (96.5mW cm−2). Experiment results and density functional theory demonstrate that the high catalysis activity is mainly caused by the surface oxygen vacancy of Fe3O4 nanoparticles. This study sheds new light on the ORR/OER bifunctional electrocatalyst design.

Engineering Co and Ru dual-metal atoms on nitrogen-doped carbon as highly efficient bifunctional oxygen electrocatalysts

Designing dual-metal atoms efficient bifunctional oxygen electrocatalyst by a one-step adsorption and a pyrolysis steps.

Supramolecular Complex Derived Carbon Nanotubes Decorated with Iron Single Atoms and Nanoclusters as Efficient Bifunctional Oxygen Electrocatalysts for Rechargeable Zn-Air Batteries

Supramolecular Complex Derived Carbon Nanotubes Decorated with Iron Single Atoms and Nanoclusters as Efficient Bifunctional Oxygen Electrocatalysts for Rechargeable Zn-Air Batteries

Ru nanoclusters confined on α/β cobalt hydroxide nanosheets as efficient bifunctional oxygen electrocatalysts for Zn–air batteries

Ru nanoclusters anchored on the α/β-Co(OH)2 nanostructures could yield bifunctional catalysts, which displayed high power density and long-cycling performance when used as the air electrode in practical Zn-air battery.