ORR Overpotential Research Articles

Self-templated formation of ZnNC microtube with high oxygen reduction reaction overpotential for Zn-based catalyst

The synthesis of hollow morphologies without employing templates and addressing the high overpotential of the oxygen reduction reaction in Zn-N4-C-based materials poses a significant challenge. In this study, we present a straightforward yet robust approach based on a self-templated metal-organic framework (MOF-based) to synthesize ZnNC microtubes and explore the reason behind its high oxygen reduction (ORR) overpotential through density functional theory (DFT) calculation. ZnNC microtubes, benefiting from the abundant Zn-N4 active sites, hierarchical porosity, and a reasonable degree of graphitization, exhibited superior ORR activity and methanol tolerance compared to the traditional precious Pt/C catalyst. On the other hand, DFT calculation shows that Zn exhibits a d10 electronic configuration and diamagnetic nature in Zn-N4 moieties confirmed by the partial density of state (PDOS), hence the main reason behind the high ORR overpotential. This study provides a novel roadmap for further engineering efforts to achieve an ideal ORR catalyst in Zn-based materials.

The defect chemistry and machine learning study 5d transition metal doped on graphitic carbon nitride for bifunctional oxygen electrocatalyst with low overpotential

Searching for highly efficient bifunctional oxygen evolution reaction/oxygen reduction reaction (OER/ORR) electrocatalysts for sustainable and renewable clean energy is vital. However, these electrocatalyst designs remain cost-prohibitive for both experimental and computational studies. This paper systematically investigates 5d transition metal (5d TM) doped into graphitic carbon nitride (g-C3N3) as potential bifunctional OER/ORR electrocatalysts by considering the defect charge states through the defect chemistry study. Our formation energies results show that 33 kinds of 5d TM doped g-C3N3 have better stabilities in the different charge states. Among them, IrN×@C54N53 (Ir occupation N), IrN•@C54N53, PtN×@C54N53 (Pt occupation N), and Iri•@C54N54 (Ir interstitial sites) exhibit lower overpotentials. They are great candidates for bifunctional OER/ORR electrocatalysts. This is because adjusting the charge states of 5d-TM@g-C3N3 can tune the interaction strength of the oxygenated intermediates. Furthermore, machine learning shows that the charge transfer of TM atoms (Qe) and total magnetic moment (μB0) are the two most essential descriptors for OER and ORR overpotential, respectively. The charged defect adjusting of the bifunctional OER/ORR activity would develop the potential electrocatalysts for energy conversion applications.

First Principles Study of the Structure-Performance Relation of Pristine Wn+1Cn and Oxygen-Functionalized Wn+1CnO2 MXenes as Cathode Catalysts for Li-O2 Batteries.

Li-O2 batteries are considered a highly promising energy storage solution. However, their practical implementation is hindered by the sluggish kinetics of the oxygen reduction (ORR) and oxygen evolution (OER) reactions at cathodes during discharging and charging, respectively. In this work, we investigated the catalytic performance of Wn+1Cn and Wn+1CnO2 MXenes (n = 1, 2, and 3) as cathodes for Li-O2 batteries using first principles calculations. Both Wn+1Cn and Wn+1CnO2 MXenes show high conductivity, and their conductivity is further enhanced with increasing atomic layers, as reflected by the elevated density of states at the Fermi level. The oxygen functionalization can change the electronic properties of WC MXenes from the electrophilic W surface of Wn+1Cn to the nucleophilic O surface of Wn+1CnO2, which is beneficial for the activation of the Li-O bond, and thus promotes the Li+ deintercalation during the charge-discharge process. On both Wn+1Cn and Wn+1CnO2, the rate-determining step (RDS) of ORR is the formation of the (Li2O)2* product, while the RDS of OER is the LiO2* decomposition. The overpotentials of ORR and OER are positively linearly correlated with the adsorption energy of the RDS LixO2* intermediates. By lowering the energy band center, the oxygen functionalization and increasing atomic layers can effectively reduce the adsorption strength of the LixO2* intermediates, thereby reducing the ORR and OER overpotentials. The W4C3O2 MXene shows immense potential as a cathode catalyst for Li-O2 batteries due to its outstanding conductivity and super-low ORR, OER, and total overpotentials (0.25, 0.38, and 0.63 V).

Enhancing oxygen reduction and evolution reactions on multi-metal N-doped graphene catalysts through catalytic activity and selectivity tuning

Metal-nitrogen-carbon (M-N-C) catalysts exhibit promising electrocatalytic properties for oxygen reduction and evolution reactions (ORR/OER) and are potential substitutes for precious metal catalysts. However, the underlying reaction mechanisms are still debated. To investigate the connection between atomic microstructures and catalytic performance, this study employs density functional theory (DFT) calculations to analyze 10 different M-N-C catalysts with varying metal atom types and ratios (Fe, Co, and Ni) on three active centers. The activities of all active sites are computed, showing notable variations in ORR/OER performance among different sites. For homonuclear M-N-C catalysts, the ORR overpotentials of Fe, Co, and Ni are 0.69, 0.26, and 1.03 V, respectively. These values change to 0.79, 0.31, and 1.00 V, respectively, for the heteronuclear M-N-C catalysts with trimetallic active centers when the reaction occurs at the Fe, Co, and Ni site. Similar trends are observed for the OER of both homonuclear and heteronuclear M-N-C catalysts in molecular models. Among Fe, Co, and Ni atoms, the Co site exhibits the most favorable ORR/OER bifunctional activity. This study provides valuable insights into selecting catalytic active sites and understanding the structure-performance relationship of M-N-C structures at a microscopic level.

Densely populated trimetallic single-atoms for durable low-temperature flexible zinc-air batteries

The fundamental challenge of trimetallic single-atoms catalysts stems from the difficulty in supporting the coexistence of different metals with their unique physicochemical features. Here, the trimetallic single-atoms electrocatalyst is constructed as a model system to explore electrocatalytic ORR/OER. The tri-metal (Fe, Co, and Ni) single-atoms loaded on nitrogen-carbon framework exhibits superior ORR/OER kinetics (E1/2 = 0.927 V, Ej=10 = 1.56 V). The flexible zinc-air batteries generate excellent power density and durability (62 mW cm−2 and 200 h at −15 °C, 291.2 mW cm−2 and 250 h at room temperature). Density functional calculations confirm that the trimetallic synergy effect outperform mono- and bimetallic effects, yielding adsorption strength close to 0. This paper describes an intuitionistic descriptor where ΔEOH* displays a volcano relationship with ORR overpotential, and establishes a generalized strategy for efficient bifunctional oxygen electrocatalyst while comprehensively understanding the structure-mechanism-activity relationship.

Theoretical study of catalytic performance of WN MXenes as cathodes for Li-O2 batteries: Effects of surface functionalization and atomic layers

Promising Li–O2 batteries suffer from high overpotentials of the oxygen evolution reaction (ηOER)/oxygen reduction reaction (ηORR) at cathodes during charging/discharging. Herein, the first-principles calculations were performed to investigate WN MXenes, including the pristine Wn+1Nn and oxygen − functionalized Wn+1NnO2 (n = 1, 2, and 3), as the potential cathode catalysts for Li − O2 batteries. Both Wn+1Nn and Wn+1NnO2 exhibit high electrical conductivity. Compared to the electrophilic W surfaces of Wn+1Nn, the nucleophilic O surfaces of Wn+1NnO2 can not only bind to Li of LixO2 to activate the Li − O bond, but also promote electron transfer to form Li+, which facilitates to the delithiation of LixO2 in the OER, thus lowering ηOER on Wn+1NnO2. Moreover, the O-functionalized surfaces can also reduce the adsorption energies of LixO2, thereby lowering ηORR and ηOER. On the other hand, reducing atomic layers of Wn+1Nn and Wn+1NnO2 can further lower ηORR and ηOER, because WN MXenes with fewer atomic layers have lower d-/p- band centers, which can weaken the adsorption of LixO2. The W2NO2 MXene not only has a high electrical conductivity but also exhibits ultra-low ORR, OER, and total overpotentials (0.12, 0.17, and 0.29 V), indicating it possesses an ultra-high catalytic performance as cathodes for Li-O2 batteries.

Designing Breathing Air-electrode and Enhancing the Oxygen Electrocatalysis by Thermoelectric Effect for Efficient Zn-air Batteries.

The sluggish kinetics and mutual interference of oxygen evolution and reduction reactions (OER and ORR) in the air electrode resulted in large charge/discharge overpotential and low energy efficiency of Zn-air batteries. In this work, we designed a breathing air-electrode configuration in Zn-air batteries using P-type Ca3Co4O9 and N-type CaMnO3 as charge and discharge thermoelectrocatalysts, respectively. The Seebeck voltages generated from thermoelectric effect of Ca3Co4O9 and CaMnO3 synergistically compensated the OER and ORR overpotentials. The carrier migration and accumulation on the cold surface of Ca3Co4O9 and CaMnO3 optimized the electronic structure of metallic sites and thus enhanced their intrinsic catalytic activity. The OER and ORR overpotentials were enhanced by 101 and 90 mV, respectively, at temperature gradient of 200 °C. The breathing Zn-air battery displayed a remarkable energy efficiency of 68.1%. This work provides an efficient avenue towards utilizing waste heat for improving the energy efficiency of Zn-air batteries.

Investigation of bifunctionality of FePc-functionalized graphene for enhanced ORR/OER activity

Iron phthalocyanine monolayer supported on a graphene substrate (GFePc) is a promising Pt-free oxygen reduction reaction catalyst. The electronic properties of GFePc can be tuned via the ligand exchange of FePc, substate doping, and defect incorporation into the graphene substrate. Boron and nitrogen were chosen as substrate dopants due to their comparability to carbon in size. Two of the most common graphene defects, single and double (585) vacancies, were chosen to represent defects that can naturally occur on the graphene substrate. Tetra-substituted phthalocyanines (carboxy-, nitro-, and amino-) and hexadeca-substituted phthalocyanines (chloro‑, fluoro-, and amino-) were tested due to their availability in the current market. Utilizing ab initio spin polarized density functional theory (DFT) calculations, the dominating pathways of both the oxygen reduction (ORR) and oxygen evolution reactions (OER) have been simulated along with defining their rate-limiting step to quantify the ORR/OER overpotentials (indicator of catalyst reactivity/performance). The DFT results show that ∼1 at.% Boron doping in conjunction with a mono-vacancy graphene substrate offers the best ORR performance but a worse OER performance when compared to the pristine GFePc. Generally, an increase in ORR activity exhibited a decrease in OER activity. A qualitative volcano correlation between electronic descriptors and ORR overpotential for modified GFePc systems was observed. The present study allows for expanded understanding and definition of substituted iron phthalocyanine functionalized graphene and the effects of both substrate modification and ligand exchange on GFePc's performance as a potential bifunctional single-metal-atom based electro-catalyst.

Transition metal atom anchored by defective WSSe monolayer as bifunctional single atom catalyst for ORR and OER

• Pt@S-WSSe and Pt@Se-WSSe are found as bifuncational SACs with high ORR/OER catalytic activity. • The ORR and OER overpotential of Pt@S-WSSe are lower compared with the previous results. • The magnetic moment is identified as an effective descriptor to evaluate the catalytic activity of TM@S/Se-WSSe. Bifunctional electrocatalysts with high catalytic activity toward oxygen reduction reaction ( O R R ) and oxygen evolution reaction ( O E R ) are key for developing efficient energy conversion and storage technology. Here, we investigated the O R R and O E R electrocatalytic activity of transition metal atoms (TM) anchored at the S and Se vacancy sites of W S S e monolayer ( T M @ S - W S S e , T M @ S e - W S S e ) via performing the first-principles calculation. Our result shows that the single atom catalysts ( S A C s ) P t @ S - W S S e and P t @ S e - W S S e have low O R R / O E R overpotentials ( η O R R / η O E R ) of 0.31/0.36 V and 0.43/0.34 V, respectively. The η O R R and η O E R at SAC P t @ S - W S S e are even lower compared with the previously studied S A C s . Besides, the Gibbs free energy changes of the key intermediate adsorption are close to the values at ideal catalyst. Our calculations demonstrate the promising potential of P t @ S - W S S e and P t @ S e - W S S e as O R R and O E R bifunctional S A C s . More importantly, the superior O R R and O E R catalytic activity of T M @ S - W S S e and T M @ S e - W S S e are well explained via the intrinsic feature of S A C s as well as the interaction between the TM atom and the intermediates. Especially, we demonstrate that the magnetic moment and the catalytic activity of S A C s T M @ S - W S S e and T M @ S e - W S S e is closely correlated. Our result provides new idea for designing highly effectual O R R and O E R bifunctional SACs.

Cooperatively interface role of surface atoms and aqueous media on single atom catalytic property for H2O2 synthesis

Direct electrosynthesis of hydrogen peroxide (H2O2) from H2 and O2 is a promising alternative to currently industrial Riedl-Pfleiderer route. Utilizing a combination of density functional theory (DFT) and ab-initio-molecular dynamic simulation (AIMD), we presented an effective computational framework to identify the cooperative role of surface atoms(e.g. O, N and S) and aqueous media on catalytic performance of single-atom catalysts (SACs) supported Nb2C MXenes. Computational results shown that both Ni/Nb2CN2 and Co/Nb2CS2 have low overpotentials of 0.17 V and 0.20 V, and the barrier of 0.89 eV and 0.67 eV for 2e- ORR under gas phase, respectively, while in aqueous phase, hydrogen bond framework on the surface promotes the transfer of proton, resulting in the lower 2e- ORR overpotential (0.05 V) in Co/Nb2CS2 and lower barrier (almost 0.01 eV) for rate-determining step (RDS) in Ni/Nb2CN2. Electronically, we found that the less-electronegativity N and S relative to O more benefit to mediate the activation degree of O2 on SACs and thereby improve catalytic selectivity. Thus, it is concluded that both surface atom and aqueous medium synergistically promote catalytic property for H2O2 synthesis.

First-principle study on catalytic activity of functionalized Ti3C2 MXene as cathode catalyst for Li–O2 batteries

Two-dimensional layered Ti3C2, one representative MXene, is notable as promising cathode catalyst for rechargeable lithium-oxygen (Li–O2) batteries. Using first-principles calculations, we construct cathode electrochemical interface catalytic model to simulate the structural evolution during discharging and charging processes, and the calculated ORR, OER and TOT overpotentials are used to quantitatively assess the catalytic activity of Ti3C2 MXene with and without O, F and OH functional groups. Interestingly, we find that the catalytic activity follows such a trend: Ti3C2O2>Ti3C2F2>Ti3C2(OH)2>Ti3C2, which suggests that O-terminated Ti3C2 MXene has great advantages and potentiality for catalyzing ORR and OER in Li–O2 batteries. This is caused by Ti3C2O2 surface shows stronger oxidation capability toward O22− compared to Ti3C2F2, Ti3C2(OH)2 and Ti3C2. The present study may provide a guideline to accelerate ORR and OER reactions of Ti3C2 MXene as cathode catalyst in Li–O2 batteries, with O-terminated group being taken into consideration.

Bimetallic Zero-Valent Alloy with Measured High-Valent Surface States to Reinforce the Bifunctional Activity in Rechargeable Zinc-Air Batteries

Among the earth-abundant catalysts for the air-electrode of metal-air batteries, success with one-component catalyst systems driving the bifunctional oxygen evolution and reduction reactions (OER and ORR) remains elusive. Herein, a cobalt–copper couple addresses this gap-area where the best performing catalyst consists of an electrically conducting backbone of 57 wt % Cu0.9Co0.1 alloy and 10 wt % Co with higher valence surface states of CoO, Cu2O, CuO, and Co3O4 with 19.7, 10, 2.9, and 0.3 wt %, respectively. Computational studies show the Co-center as the active site for OER and ORR, while charge transfer from the Co to Cu center accumulates the electronic charge at the junction between the surface CoO and the alloy core facilitating the adsorption of oxygenated species. The 24 h air-oxidized electrodeposited-catalyst shows OER overpotentials of 225, 290, and 312 mV at 10, 50, and 100 mA cm–2, respectively, with at least 150 h operational stability at 1.55 V versus reversible hydrogen electrode (RHE). By electrodepositing the catalyst on high-priced Ni-foam, record-low overpotentials of 190, 281, and 298 mV are observed at 10, 50, and 100 mA cm–2. Since the ORR overpotential is only 550 mV at −1 mA cm–2 on CFP, the bifunctionality index (BI) subsides to 0.775 V. The rechargeable zinc-air battery (ZAB) delivers a stellar 948 mA·h·gZn–1 specific capacity, 68.8 mW cm–2 power density, and uninterrupted one-week operational stability. Even in the presence of Cl– ions in alkaline artificial seawater, the OER overpotential is retained at 240 mV at 10 mA cm–2 and the ZAB specific capacity is slightly reduced to 759.5 mA·h·gZn–1. A synergistic bimetallic composition, measured higher valence surface states with singly occupied eg orbitals, and branched morphology, facilitates the optimum adsorption and desorption of the intermediates.

Design of Heterostructures of MXene/Two-Dimensional Organic Frameworks for Na-O2 Batteries with a New Mechanism and a New Descriptor.

Na-O2 batteries are promising candidates to replace Li-O2 batteries for their excellent performance. However, the charge overpotential of Na-O2 batteries is usually too high. In this work, we designed combinations of MXene and a two-dimensional organic framework for Na-O2 batteries. The results show that the Ti2CO2/Cu-BHT has low OER and ORR overpotentials of 0.24 and 0.32 V, respectively. Besides this, the conductivity and the adsorption energy to Na+ (Eads(Na+)) are promoted due to the charge transfer between layers. We also found that the OER and ORR overpotentials are negatively and positively correlated with Eads(Na+), respectively, where Ti2CO2/Cu-BHT has a moderate Eads(Na+) (-2.20 eV) and, therefore, has good performance. Moreover, a new mechanism called the Na encapsulation mechanism was proposed on a two-dimensional organic framework surface. Through least absolute shrinkage and selection operator (LASSO) regression, we found a new descriptor that consists of inherent properties that could help us screen better heterostructures for Na-O2 batteries.

Labile oxygen participant adsorbate evolving mechanism to enhance oxygen reduction in SmMn2O5 with double-coordinated crystal fields

The oxygen reduction reaction mechanism (LAM) was proposed over the Mn-based mullite SmMn2O5 with dual coordination crystal fields to reduce the ORR overpotential.

Kinetically Stable Oxide Overlayers on Mo3 P Nanoparticles Enabling Lithium-Air Batteries with Low Overpotentials and Long Cycle Life.

The main drawbacks of today's state-of-the-art lithium-air (Li-air) batteries are their low energy efficiency and limited cycle life due to the lack of earth-abundant cathode catalysts that can drive both oxygen reduction and evolution reactions (ORR and OER) at high rates at thermodynamic potentials. Here, inexpensive trimolybdenum phosphide (Mo3 P) nanoparticles with an exceptional activity-ORR and OER current densities of 7.21 and 6.85 mA cm-2 at 2.0 and 4.2 V versus Li/Li+ , respectively-in an oxygen-saturated non-aqueous electrolyte are reported. The Tafel plots indicate remarkably low charge transfer resistance-Tafel slopes of 35 and 38 mV dec-1 for ORR and OER, respectively-resulting in the lowest ORR overpotential of 4.0 mV and OER overpotential of 5.1 mV reported to date. Using this catalyst, a Li-air battery cell with low discharge and charge overpotentials of 80 and 270 mV, respectively, and high energy efficiency of 90.2% in the first cycle is demonstrated. A long cycle life of 1200 is also achieved for this cell. Density functional theory calculations of ORR and OER on Mo3 P (110) reveal that an oxide overlayer formed on the surface gives rise to the observed high ORR and OER electrocatalytic activity and small discharge/charge overpotentials.

Trifunctional Single‐Atomic Ru Sites Enable Efficient Overall Water Splitting and Oxygen Reduction in Acidic Media

Development of cost-effective, active trifunctional catalysts for acidic oxygen reduction (ORR) as well as hydrogen and oxygen evolution reactions (HER and OER, respectively) is highly desirable, albeit challenging. Herein, single-atomic Ru sites anchored onto Ti3 C2 Tx MXene nanosheets are first reported to serve as trifunctional electrocatalysts for simultaneously catalyzing acidic HER, OER, and ORR. A half-wave potential of 0.80 V for ORR and small overpotentials of 290 and 70 mV for OER and HER, respectively, at 10 mA cm-2 are achieved. Hence, a low cell voltage of 1.56 V is required for the acidic overall water splitting. The maximum power density of an H2 -O2 fuel cell using the as-prepared catalyst can reach as high as 941 mW cm-2 . Theoretical calculations reveal that isolated Ru-O2 sites can effectively optimize the adsorption of reactants/intermediates and lower the energy barriers for the potential-determining steps, thereby accelerating the HER, ORR, and OER kinetics.

Sulphur modulated Ni3FeN supported on N/S co-doped graphene boosts rechargeable/flexible Zn-air battery performance

Exploring feasible strategy for preparation of sulfur (S) modulated NiFe compounds and meanwhile clarifying the performance promoting mechanism of such catalysts has triggered numerous interest in rechargeable Zinc-air battery research field. Herein, S modulated Ni3FeN supported on N/S co-doped graphene (S-Ni3FeN/NSG) is synthesized via controlling the nitriding process of NiFe disulfides. The beneficial effect of the design strategy and S decoration on electrocatalytic activity are determined and analysed systematacially. The S-Ni3FeN/NSG-700 delivers excellent bifunctional oxygen electrocatalysis performance with half-wave potential of 0.878 V for ORR and low OER overpotential of 260 mV at 10 mA cm−2. Density Functional Theory (DFT) calculations demonstrate that S decoration effectively promotes the formation of OOH* intermediates and observably decreases the maximum of change of the Gibbs free energies for four primitive OER steps. Notably, when S-Ni3FeN/NSG-700 as air electrode applied in Zn-air battery test, the device shows superb durability for 1200 discharge/charge cycles at 10 mA cm-2. The corresponding all-solid Zinc-air battery exhibits excellent mechanical flexibility and a high power density of 140.1 mW cm-2. Two Zinc-air batteries in series can long-term stably power a self-made water-splitting device. This work provides new insights into highly efficient and low-cost bifunctional oxygen electrocatalyst designing.

Flexible self-supported bi-metal electrode as a highly stable carbon- and binder-free cathode for large-scale solid-state zinc-air batteries

Flexible (Ni, Co)3O4 nanosheets are grown on the surface of a Ni-foam by a facile electrodeposition coupled electrochemical oxidation process. The as-synthesized (Ni, Co)3O4 nanosheets are self-supported and can be directly used as the oxygen electrode without an addition of carbon or binder. As expect, the physical measurements and density functional theory (DFT) calculation reveal that Ni doping decreases Co3O4 surface activity towards the O, OH, OOH species, thus reducing the OER and ORR over-potentials. As a result, the (Ni, Co)3O4@Ni-foam electrode exhibits an unprecedented performance with a lower potential gap (⊗E: 0.57 V) than Pt/C+IrO2. This nanosheet can be readily applied as an electrode for Zn-air battery with a large area up to 24 cm2. The improved performance of this large-area electrode includes: a small charge-discharge voltage drop (0.56 V) and super stability with a high voltage efficiency of 69 % across all cycles.

Trifunctional Single-Atomic Ru Sites Enable Efficient Overall Water Splitting and Oxygen Reduction in Acidic Media

Development of cost-effective, active trifunctional catalysts for acidic oxygen reduction (ORR) as well as hydrogen- and oxygen-evolution reactions (HER and OER, respectively) is highly desirable, albeit challenging. Herein, single-atomic Ru sites anchored onto Ti3C2Tx MXene nanosheets are first reported to serve as trifunctional electrocatalysts for simultaneously catalyzing acidic HER, OER, and ORR. A half-wave potential of 0.80 V for ORR and small overpotentials of 290 mV and 70 mV for OER and HER, respectively, at 10 mA cm−2 are achieved. Hence, a low cell voltage of 1.56 V is required for the acidic overall water splitting. The maximum power density of an H2–O2 fuel cell using the as-prepared catalyst can reach as high as 941 mW cm−2. Theoretical calculations revealed that isolated Ru–O2 sites can effectively optimize the adsorption of reactants/intermediates and lower the energy barriers for the potential-determining steps, thereby accelerating the HER, ORR, and OER kinetics.

Trimetallic Mn‐Fe‐Ni Oxide Nanoparticles Supported on Multi‐Walled Carbon Nanotubes as High‐Performance Bifunctional ORR/OER Electrocatalyst in Alkaline Media

AbstractDiscovering precious metal‐free electrocatalysts exhibiting high activity and stability toward both the oxygen reduction (ORR) and the oxygen evolution (OER) reactions remains one of the main challenges for the development of reversible oxygen electrodes in rechargeable metal–air batteries and reversible electrolyzer/fuel cell systems. Herein, a highly active OER catalyst, Fe0.3Ni0.7OX supported on oxygen‐functionalized multi‐walled carbon nanotubes, is substantially activated into a bifunctional ORR/OER catalyst by means of additional incorporation of MnOX. The carbon nanotube‐supported trimetallic (Mn‐Ni‐Fe) oxide catalyst achieves remarkably low ORR and OER overpotentials with a low reversible ORR/OER overvoltage of only 0.73 V, as well as selective reduction of O2 predominantly to OH−. It is shown by means of rotating disk electrode and rotating ring disk electrode voltammetry that the combination of earth‐abundant transition metal oxides leads to strong synergistic interactions modulating catalytic activity. The applicability of the prepared catalyst for reversible ORR/OER electrocatalysis is evaluated by means of a four‐electrode configuration cell assembly comprising an integrated two‐layer bifunctional ORR/OER electrode system with the individual layers dedicated for the ORR and the OER to prevent deactivation of the ORR activity as commonly observed in single‐layer bifunctional ORR/OER electrodes after OER polarization.