Enhancing Zn2+ Storage Performance by Constructing the Interfaces Between VO2 and Co-N-C Layers.

Vanadium oxides have aroused attention as cathode materials in aqueous zinc-ion batteries (AZIBs) due to their low cost and high safety. However, low ion diffusion and vanadium dissolution often lead to capacity decay and deteriorating stability during cycling. Herein, vanadium dioxides (VO2) nanobelts are coated with a single-atom cobalt dispersed N-doped carbon (Co-N-C) layer via a facile calcination strategy to form Co-N-C layer coated VO2 nanobelts (VO2@Co-N-C NBs) for cathodes in AZIBs. Various in-/ex situ characterizations demonstrate the interfaces between VO2 layers and Co-N-C layers can protect the VO2 NBs from collapsing, increase ion diffusion, and enhance the Zn2+ storage performance. Additional density functional theory (DFT) simulations demonstrate that Co─O─V bonds between VO2 and Co-N-C layers can enhance interfacial Zn2+ storage. Moreover, the VO2@Co-N-C NBs provided an ultrahigh capacity (418.7 mAh g-1 at 1 A g-1), outstanding long-term stability (over 8000 cycles at 20 A g-1), and superior rate performance.

Ultrathin Co-N-C Layer Modified Pt-Co Intermetallic Nanoparticles Leading to a High-Performance Electrocatalyst toward Oxygen Reduction and Methanol Oxidation.

The development of low platinum-based alloy electrocatalysts is crucial to accelerate the commercialization of fuel cells, yet remains a synthetic challenge and an incompatibility between activity and stability. Herein, a facile procedure to fabricate a high-performance composite that comprises Pt-Co intermetallic nanoparticles (IMNs) and Co, N co-doped carbon (Co-N-C) electrocatalyst is proposed. It is prepared by direct annealing of homemade carbon black-supported Pt nanoparticles (Pt/KB) covered with a Co-phenanthroline complex. During this process, most of Co atoms in the complex are alloyed with Pt to form ordered Pt-Co IMNs, while some Co atoms are atomically dispersed and doped in the framework of superthin carbon layer derived from phenanthroline, which is coordinated with N to form Co-Nx moieties. Moreover, the Co-N-C film obtained from complex is observed to cover the surface of Pt-Co IMNs, which prevent the dissolution and agglomeration of nanoparticles. The composite catalyst exhibits high activity and stability toward oxygen reduction reactions (ORR) and methanol oxidation reactions (MOR), delivering outstanding mass activities of 1.96 and 2.92 A mgPt -1 for ORR and MOR respectively, owing to the synergistic effect of Pt-Co IMNs and Co-N-C film. This study may provide a promising strategy to improve the electrocatalytic performance of Pt-based catalysts.

Exploiting the Synergistic Electronic Interaction between Pt-Skin Wrapped Intermetallic PtCo Nanoparticles and Co-N-C Support for Efficient ORR/EOR Electrocatalysis in a Direct Ethanol Fuel Cell.

The development of low-Pt catalysts with high activity and durability is critical for fuel cells. Here, Pt-skin wrapped sub-5 nm PtCo intermetallic nanoparticles are successfully mounted on single atom Co-N-C support by exploiting the barrier effect of Co-anchor. According to a collaborative experimental and computational investigation, the increased oxygen reduction reaction activity of PtCo/Co-N-C arises from the direct electron transfer from PtCo to Co-N-C, and the resulting optimal d-band center of Pt. Owing to such unique electronic structure interaction and synergistic effect, the specific and mass activities of PtCo/Co-N-C are up to 4.20 mA cm-2 and 2.71 A mgPt-1 , respectively, with barely degraded stability after 40 000 CV cycles. The PtCo/Co-N-C also exhibits outstanding activity as an ethanol electrocatalyst. This work shows a new and effective route to boost the overall efficiency of direct ethanol fuel cells in acidic media by integrating intermetallic low-Pt alloys and single atom carbon support.

Constructing Co-N-C Catalyst via a Double Crosslinking Hydrogel Strategy for Enhanced Oxygen Reduction Catalysis in Fuel Cells.

Exploiting platinum-group-metal (PGM)-free electrocatalysts with remarkable activity and stability toward oxygen reduction reaction (ORR) is of significant importance to the large-scale commercialization of proton exchange membrane fuel cells (PEMFCs). Here, a high-performance and anti-Fenton reaction cobalt-nitrogen-carbon (Co-N-C) catalyst is reported via employing double crosslinking (DC) hydrogel strategy, which consists of the chemical crosslinking between acrylic acid (AA) and acrylamide (AM) copolymerization and metal coordinated crosslinking between Co2+ and P(AA-AM) copolymer. The resultant DC hydrogel can benefit the Co2+ dispersion via chelated Co-N/O bonds and relieve metal agglomeration during the subsequent pyrolysis, resulting in the atomically dispersed Co-Nx/C active sites. By optimizing the ratio of AA/AM, the optimal P(AA-AM)(5-1)-Co-N catalyst exhibits a high content of nitrogen doping (12.36 at%) and specific surface area (1397 m2 g-1 ), significantly larger than that of the PAA-Co-N catalyst (10.59 at%/746 m2 g-1 ) derived from single crosslinking (SC) hydrogel. The electrochemical measurements reveal that P(AA-AM)(5-1)-Co-N possesses enhanced ORR activity (half-wave potential (E1/2 ) ≈0.820 V versus the reversible hydrogen electrode (RHE)) and stability (≈4 mV shift in E1/2 after 5000 potential cycles in 0.5 m H2 SO4 at 60 ºC) relative to PAA-Co-N, which is higher than most Co-N-C catalysts reported so far.

High-pressure vapor-solid transformation of 2D template to derive 2D Co-N-C electrocatalysts for oxygen reduction reaction.

Two-dimensional (2D) cobalt zeolitic imidazolate frameworks (ZIF-67) have attracted significant research interests to synthesize cobalt and nitrogen co-doped carbon-based (Co-N-C) catalyst for oxygen reduction reaction (ORR). However, most of the current synthetic approaches of 2D ZIF-67 are energy-intensive, environmentally hazardous and low-yield. Herein, a feasible and efficient 'morphology-retaining method via a high-pressure vapor-solid reaction' are reported to synthesize 2D ZIF-67 nanosheets by using 2D cobalt carbonate hydroxide template. In the strategy, the high-pressure vapor caused by sublimation of 2-Melm and the pores formed from effusion of CO2during transformation ensure the complete transformation from 2D template to 2D ZIF-67. The corresponding 2D Co-N-C catalyst exhibits comparable ORR electrocatalytic activity and better stability than Pt/C in alkaline media. The present method is expected to offer a feasible and universal way to efficiently synthesize 2D M-N-C catalysts.

Dynamically Unveiling Metal-Nitrogen Coordination during Thermal Activation to Design High-Efficient Atomically Dispersed CoN4 Active Sites.

We elucidate the structural evolution of CoN4 sites during thermal activation by developing a zeolitic imidazolate framework (ZIF)-8-derived carbon host as an ideal model for Co2+ ion adsorption. Subsequent in situ X-ray absorption spectroscopy analysis can dynamically track the conversion from inactive Co-OH and Co-O species into active CoN4 sites. The critical transition occurs at 700 °C and becomes optimal at 900 °C, generating the highest intrinsic activity and four-electron selectivity for the oxygen reduction reaction (ORR). DFT calculations elucidate that the ORR is kinetically favored by the thermal-induced compressive strain of Co-N bonds in CoN4 active sites formed at 900 °C. Further, we developed a two-step (i.e., Co ion doping and adsorption) Co-N-C catalyst with increased CoN4 site density and optimized porosity for mass transport, and demonstrated its outstanding fuel cell performance and durability.

In Situ CVD Derived Co-N-C Composite as Highly Efficient Cathode for Flexible Li-O2 Batteries.

To promote the development of high energy Li-O2 batteries, it is important to design and construct a suitable and effective oxygen-breathing cathode. Herein, activated cobalt-nitrogen-doped carbon nanotube/carbon nanofiber composites (Co-N-CNT/CNF) as the effective cathodes for Li-O2 batteries are prepared by in situ chemical vapor deposition (CVD). The unique architecture of these electrodes facilitates the rapid oxygen diffusion and electrolyte penetration. Meanwhile, the nitrogen-doped carbon nanotube/carbon nanofiber (N-CNT/CNF) and Co/CoNx serve as reaction sites to promote the formation/decomposition of discharge product. Li-O2 batteries with Co-N-CNT/CNF cathodes exhibit superior electrochemical performance in terms of a positive discharge plateau (2.81 V) and a low charge overpotential (0.61 V). Besides, Li-O2 batteries also present a high discharge capacity (11512.4 mAh g-1 at 100 mA g-1 ), and a long cycle life (130 cycles). Meanwhile, the Co-N-CNT/CNF cathode also has an excellent flexibility, thus the assembled flexible battery with Co-N-CNT/CNF can work normally and hold a wonderful capacity rate under various bending conditions.

Interfacial OOH* mediated Fe(II) regeneration on the single atom Co-N-C catalyst for efficient Fenton-like processes.

Fe(II) regeneration is decisive for highly efficient H2O2-based Fenton-like processes, but the role of cobalt-containing reactive sites in promoting Fe(II) regeneration was overlooked. Herein, a single atom Co-N-C catalyst was employed in Fe(II)/H2O2 system to promote the degradation of diverse organic contaminants. The EPR and quenching experiments indicated Co-N-C significantly enhanced the generation of superoxide species, and accelerated hydroxyl radical generation for pollutant degradation. The electrochemical and surface composition analyses demonstrated the enhanced H2O2 activation and Fe(III)/Fe(II) recycling on the catalyst. Furthermore, in-situ Raman characterization with shell-isolated gold nanoparticles was employed to visualize the interfacial reactive intermediates and their time-resolved interaction. The accumulation of interfacial CoOOH* was confirmed when Co-N-C activated H2O2 alone, but it rapidly transformed into FeOOH* upon Fe(II) addition. Besides, the temporal variation of OOH* intermediates and the relative intensity of Co(III)-O and Co(IV)=O peaks depicted the dynamic interaction of reactive intermediates along the H2O2 consumption. With this basis, we proposed a mechanism of interfacial OOH* mediated Fe(II) regeneration, which overcame the kinetical limitation of Fe(II)/H2O2 system. Therefore, this study provided a primary effort to elucidate the overlooked role of interfacial CoOOH* in the Fenton-like processes, which may inspire the design of more efficient catalysts.

In Situ Flash Synthesis of Ultra-High-Performance Metal Oxide Anode through Shunting Current-Based Electrothermal Shock.

The synthesis of anode materials plays an important role in determining the production efficiency, cost, and performance of lithium-ion batteries (LIBs). However, a low-cost, high-speed, scalable manufacturing process of the anode with the desired structural feature for practical technology adoption remains elusive. In this study, we propose a novel method called in situ flash shunt-electrothermal shock (SETS) which is controllable, fast, and energy-saving for synthesizing metal oxide-based materials. By using the example of direct electrothermal decomposition of ZIF-67 precursor loaded onto copper foil support, we achieve rapid (0.1-0.3 s) pyrolysis and generate porous hollow cubic structure material consisting of carbon-coated ultrasmall (10-15 nm) subcrystalline CoO/Co nanoparticles with controllable morphology. It was shown that CoO/Co@N-C exhibits prominent electrochemical performance with a high reversible capacity up to 1503.7 mA h g-1 after 150 cycles at 0.2 A g-1and stable capacities up to 434.1 mA h g-1 after 400 cycles at a high current density of 6 A g-1. This fabrication technique integrates the synthesis of active materials and the formation of electrode sheets into one process, thus simplifying the preparation of electrodes. Due to the simplicity and scalability of this process, it can be envisaged to apply it to the synthesis of metal oxide-based materials and to achieve large-scale production in a nanomanufacturing process.

Tuning the Electronic Structure of a Novel 3D Architectured Co-N-C Aerogel to Enhance Oxygen Evolution Reaction Activity.

Hydrogen generation through water electrolysis is an efficient technique for hydrogen production, but the expensive price and scarcity of noble metal electrocatalysts hinder its large-scale application. Herein, cobalt-anchored nitrogen-doped graphene aerogel electrocatalysts (Co-N-C) for oxygen evolution reaction (OER) are prepared by simple chemical reduction and vacuum freeze-drying. The Co (0.5 wt%)-N (1 wt%)-C aerogel electrocatalyst has an optimal overpotential (0.383 V at 10 mA/cm2), which is significantly superior to that of a series of M-N-C aerogel electrocatalysts prepared by a similar route (M = Mn, Fe, Ni, Pt, Au, etc.) and other Co-N-C electrocatalysts that have been reported. In addition, the Co-N-C aerogel electrocatalyst has a small Tafel slope (95 mV/dec), a large electrochemical surface area (9.52 cm2), and excellent stability. Notably, the overpotential of Co-N-C aerogel electrocatalyst at a current density of 20 mA/cm2 is even superior to that of the commercial RuO2. In addition, density functional theory (DFT) confirms that the metal activity trend is Co-N-C > Fe-N-C > Ni-N-C, which is consistent with the OER activity results. The resulting Co-N-C aerogels can be considered one of the most promising electrocatalysts for energy storage and energy saving due to their simple preparation route, abundant raw materials, and superior electrocatalytic performance.

Single-atom nanozymes Co-N-C as an electrochemical sensor for detection of bioactive molecules.

A properly designed sensing interface is crucial for the accurate and sensitive detection of biologically active molecules. Single-atom nanozymes from transition metal and nitrogen-doped carbon materials (M-N-C) have caught attention owing to their large surface area and strong bionic enzyme activity. Herein, a three-dimensional layered electrochemical electrode consisting of a Co-N-C nanoenzyme embedded in a reduced graphene oxide aerogel was prepared for the detection of hydrogen peroxide (H2O2), dopamine (DA) and uric acid (UA). Due to its unique three-dimensional layered structure, rGA has excellent electrical conductivity and high material loading and is used to enhance the electrocatalytic performance of Co-N-C. The combination of single-atom nanozymes and electrochemical detection shows unique advantages in catalytic activity and selectivity. The limit of detection and detection range are 0.74 µM and 3-2991 µM respectively for H2O2. Furthermore, it has been successfully implemented for the in-situ detection of H2O2 in living cells. In addition, their simultaneous detection is also realized by the sensors for DA and UA. And it can accurately capture the signal of UA and DA in the urine. Meanwhile, the electrode displays satisfactory stability and repeatability. Therefore, this paper provides a new detection strategy for a variety of bioactive molecules, showing great potential in cell biology, pathophysiology and diagnostics.

Cobalt-Nitrogen Co-Doped Carbon as Highly Efficient Oxidase Mimics for Colorimetric Assay of Nitrite.

Transition metal-N-doped carbon has been demonstrated to mimic natural enzyme activity; in this study, cobalt-nitrogen co-doped carbon (Co-N-C) nanomaterial was developed, and it could be an oxidase mimic. Firstly, Co-N-C with oxidase-like activity boosts the chromogenic reaction of 3,3',5,5'-tetramethylbenzidine (TMB) to produce the oxidized TMB (oxTMB). And the aromatic primary amino group of oxTMB reacts with nitrite (NO2-) to form diazo groups. Based on this background, we developed a cascade system of a Co-N-C-catalyzed oxidation reaction and a diazotization reaction for nitrite determination. The low detection limit (0.039 µM) indicates that Co-N-C is superior compared with the vast majority of previously reported nitrite assays. This study not only provides a novel nanozyme with sufficiently dispersed active sites, but it also further applies it to the determination of nitrite, which is expected to expand the application of nanozymes in colorimetric analysis.

Unveiling the role of cobalt species in the Co/N-C catalysts-induced peroxymonosulfate activation process.

In this study, three Co/N-C catalysts were prepared by pyrolysis of bimetallic zeolitic imidazole frameworks with different Co/Zn ratio, and the critical active Co species in peroxymonosulfate (PMS) activation was investigated. The three catalysts had distinct cobalt species but similar N configuration and graphitization degree. The Co species were distributed as single atoms (Co SAs) at a Co/Zn molar ratio of 1:8, while Co nanoclusters (Co NCs) and Co nanoparticles (NPs) would be formed with further increase in Co content. The degradation efficiency of BPA did not show correlation with the increasing of Co content in catalyst. Based on the catalytic performance comparison and reactive species detection, Co SAs was identified as active sites, which could interact with PMS to generate 1O2 via path of PMS→HOO*→O*→1O2. However, the role of NCs and NPs in directly activating PMS was negligible. In addition, the increase of Co content in Co/N-C catalyst would result in mass cobalt leaching, which enhanced the BPA degradation via homogeneous catalytic reactions with CoIV as reactive species. It is an effective way to design the Co/N-C catalyst with high catalytic activity and stability via regulating the formation of Co SAs.

Co, N co-doped hierarchical porous carbon as efficient cathode electrocatalyst and its impact on microbial community of anode biofilm in microbial fuel cell.

The exploration of low-cost, long-term stable, and highly electrochemically active cathode catalysts is important for the practical application of microbial fuel cell (MFC). In this work, a series of the 3D hierarchical porous Co-N-C (3DHP Co-N-C) materials are designed and synthesized by a metal-organic framework ZIF-67 as a precursor and SiO2 sphere of different sizes as the hard template. The 3DHP Co-N-C-2 with 129 nm macropore exhibits excellent ORR performance in 0.1 M KOH solution with a half-wave potential of 0.80 V vs. RHE and superior durability than Pt/C (20%) due to the specific macropore-mesopore-micropore structure that exposes a large number of active sites and accelerates the electrolyte transport and oxygen diffusion. The MFC with 3DHP Co-N-C-2 as the cathode catalysts shows excellent performance with a maximum power density of 426.9±7.87 mW m-2 and favorable durability after 50 d of operation. In addition, 16s rDNA results reveal the presence of different dominant electrogenic bacteria and different abundance of important non-electrogenic bacteria in the anode biofilm in MFCs using cathode catalysts with different ORR activity. And 3DHP Co-N-C-2 was found to be beneficial to the synergistic effect of electrogenic and non-electrogenic bacteria. This study explores electrocatalysts in terms of both electrocatalytic activity and anode microorganisms, providing new and comprehensive insights into the power generation of MFC.

Antioxidant identification using a colorimetric sensor array based on Co-N-C nanozyme.

Here we develop a simple and effective nose/tongue sensor array based on Co-N-C single-atom nanozymes-3,3',5,5'-tetramethylbenzidine (TMB)-H2O2 for colorimetric discrimination of antioxidants, which makes use of the color reaction of TMB oxidation by H2O2 in two different pH (3.8 and 4.6) environments under the catalysis of Co-N-C nanoenzyme with peroxidase-like activity. Different antioxidants have varying reducing ability to the oxidation products of TMB (oxTMB), thus resulting in differential absorbance and color changes. Linear discriminant analysis (LDA) results indicate that the sensor array successfully identified 7 antioxidants, i.e., glutathione (GSH), ascorbic acid (AA), cysteine (Cys), tannin (TA), Catechin (C), dopamine (DA), and uric acid (UA) in both buffer and even serum samples. Additionally, the performance of the sensor array was validated with antioxidant mixtures, individual antioxidants with different concentrations, and target antioxidants and interfering substances. In general, the versatile sensor array based on Co-N-C single-atom nanozymes provides an excellent strategy for identifying a variety of antioxidants, which exhibits a broad application prospect in medical diagnosis.

Mass Transfer in a Co/N/C Catalyst Layer for the Anion Exchange Membrane Fuel Cell.

Developing highly efficient non-noble metal catalysts for the cathode of fuel cells is an urgent requirement for reducing the cost. Although the intrinsic activity of non-noble metal materials has been greatly improved, the fuel cell performance is also determined by the mass transfer within the catalyst layer (CL), particularly at high current density. Electrochemical impedance spectroscopy (EIS) combined with rotating disk electrode (RDE) analysis is a powerful tool to quantitatively analyze the influence of the structural properties on CL performance. Here, Co/N/C CLs with gradient pore structures are constructed based on the controllable synthesis of zeolitic imidazolate framework (ZIF)-derived catalyst. The influences of the carbon support, active site, and catalyst loading are comprehensively studied by EIS in different regions (kinetic and mixed-diffusion). The results indicate that a high micro-/mesopore ratio is beneficial to increasing the density of active sites while reducing the mass-transfer efficiency. Inversely, abundant mesopores promote mass transfer, but they result in low active site density. By carefully adjusting the pore structure and chemical composition of the ZIF-derived catalyst, the Co/N/C CL shows a low mass-transfer resistance (95.5 Ω at 0.75 V vs RHE). This work demonstrates the importance of mass transfer within the fuel cell CL, beyond seeking only high activity.

Atomic Metal Vacancy Modulation of Single-Atom Dispersed Co/N/C for Highly Efficient and Stable Air Cathode.

Metal-air batteries have received great attention as a new energy supply for next-generation electronic devices. However, their widespread application is still hindered by several challenges including sluggish kinetics of the cathodic reactions and undesirable stability of the air cathode due to the possible deposition of the discharge product. Herein, we propose an atomic metal vacancy modulation of a single-atom dispersed Co/N/C cathode to provide the zinc-air battery with both reduced overpotential and enhanced stability. As illustrated by theoretical calculations and electrochemical measurements, deliberate introduction of metal vacancies would modulate the electronic structure and contribute to enhanced catalytic activity, affording the catalyst with a half-wave potential of 0.89 V versus reversible hydrogen electrode and an overall oxygen electrode potential gap of 0.72 V. Moreover, abundant pyridinic-N groups are exposed due to the removal of metal centers, generating strong Lewis basicity to effectively prevent the access of negatively charged zincate ions and realize the nondeposition of ZnO on the air cathode. Rechargeable zinc-air battery assembled with such an air cathode delivers superior cyclic performance with low discharge/charge overpotential and negligible plateau gap increase of only 0.05 V for 1000 cycles. Flexible all-solid-state battery demonstrates robust durability of over 35 h and excellent flexibility to light-up a light-emitting diode (LED) rose, indicating its potential feasibility as a flexible and safe power source for modern life.

The Co-N-C Catalyst Synthesized With a Hard-Template and Etching Method to Achieve Well-Dispersed Active Sites for Ethylbenzene Oxidation.

Biomass obtained from organic residues gradually becomes one of the optimal renewable feedstock of value added chemicals. Herein, the Co-N-C catalyst was prepared via a hard-template and etching method using the casein as C and N sources, magnesium oxide as the template, and cobalt porphyrin as the metal precursor. The obtained Co-N-C catalyst exhibited excellent catalytic performance for selective oxidation of ethylbenzene with a conversion rate of 96.5% under mild conditions. Moreover, the catalysts were investigated by techniques such as BET, XRD, Raman, transmission electron microscopic (TEM), and X-ray photoelectron spectroscopy (XPS). The results showed that the etching progress could improve the dispersion of Co and the exposure of active sites. Herein, the efficient oxidation of ethylbenzene was attributed to the well-dispersed Co-N species and the increased specific surface area.

Co Nanoislands Rooted on Co-N-C Nanosheets as Efficient Oxygen Electrocatalyst for Zn-Air Batteries.

Developing non-precious-metal bifunctional oxygen reduction and evolution reaction (ORR/OER) catalysts is a major task for promoting the reaction efficiency of Zn-air batteries. Co-based catalysts have been regarded as promising ORR and OER catalysts owing to the multivalence characteristic of cobalt element. Herein, the synthesis of Co nanoislands rooted on Co-N-C nanosheets supported by carbon felts (Co/Co-N-C) is reported. Co nanosheets rooted on the carbon felt derived from electrodeposition are applied as the self-template and cobalt source. The synergistic effect of metal Co islands with OER activity and Co-N-C nanosheets with superior ORR performance leads to good bifuctional catalytic performances. Wavelet transform extended X-ray absorption fine spectroscopy and X-ray photoelectron spectroscopy certify the formation of Co (mainly Co0 ) and the Co-N-C (mainly Co2+ and Co3+ ) structure. As the air-cathode, the assembled aqueous Zn-air battery exhibits a small charge-discharge voltage gap (0.82 V@10 mA cm-2 ) and high power density of 132 mW cm-2 , outperforming the commercial Pt/C catalyst. Additionally, the cable flexible rechargeable Zn-air battery exhibits excellent bendable and durability. Density functional theory calculation is combined with operando X-ray absorption spectroscopy to further elucidate the active sites of oxygen reactions at the Co/Co-N-C cathode in Zn-air battery.

Engineering of Nitrogen Coordinated Single Cobalt Atom Moieties for Oxygen Electroreduction.

The nitrogen coordinated single cobalt atoms embedded in carbon matrix, i.e., Co/N/C material, is cost-efficient and free from iron-ion induced Fenton reagent, which has been thus considered as a promising candidate to replace the well-accepted Pt-based and Fe/N/C materials for oxygen reduction reaction (ORR). Recently, the pyrolysis of metal-organic framework (MOF) precursors has been investigated to achieve well-defined Co/N/C catalysts with high ORR activity. However, the relationships among the composition/structure of MOF precursor, the derived catalysts, and ORR performance have been rarely touched in specialty, while the regulations to achieve single-atom Co/N/C catalysts derived from MOF are confusing. Herein, we engineer several Co-doped MOF (zeolitic imidazolate frameworks, to be specific) precursors with different compositions and structures by tuning synthesis protocols (e.g., ratios, cobalt sources, and reaction time) and investigate the derived catalysts and their ORR properties. The regulations to single-atom Co/N/C are revealed in this work. The superior ORR activity and durability of the optimized Co/N/C catalysts are revealed and attributed to the well-defined Co-Nx moieties and their stable nanostructures.