Carbon Vacancies Research Articles

Machine learning of carbon vacancy formation energy in high-entropy carbides

Carbon vacancies as intrinsic defects in high-entropy carbides (HECs) strongly affect their physical and chemical properties, it is important to understand the details of vacancy formation at an atomic level. In this work, 1280 carbon vacancies are investigated via high-throughput density functional theory (HT-DFT) calculations and machine learning (ML) models on their formation energies. We found that more than half of the carbon vacancies are preferentially surrounded by three types of cations, with Hf less likely to be present. The role of metal cations in promoting the formation of carbon vacancies is: Nb＞Ta＞Zr＞Hf, indicating the possibility to modify the carbon vacancy concentration by change the cation elemental ratios. A random forest model was trained on DFT results to predict vacancy formation energies with a mean absolute error of 54 meV. The feature importance analysis is consistent with the analysis of the DFT results.

Charge Trap States of SiC Power TrenchMOS Transistor under Repetitive Unclamped Inductive Switching Stress.

Silicon carbide (SiC) has been envisioned as an almost ideal material for power electronic devices; however, device reliability is still a great challenge. Here we investigate the reliability of commercial 1.2-kV 4H-SiC MOSFETs under repetitive unclamped inductive switching (UIS). The stress invoked degradation of the device characteristics, including the output and transfer characteristics, drain leakage current, and capacitance characteristics. Besides the shift of steady-state electrical characteristics, a significant change in switching times points out the charge trapping phenomenon. Transient capacitance spectroscopy was applied to investigate charge traps in the virgin device as well as after UIS stress. The intrinsic traps due to metal impurities or Z1,2 transitions were recognized in the virgin device. The UIS stress caused suppression of the second stage of the Z1,2  transition, and only the first stage, Z10, was observed. Hence, the UIS stress is causing the reduction of multiple charging of carbon vacancies in SiC-based devices.

Interlayer Charge Transfer Over Graphitized Carbon Nitride Enabling Highly-Efficient Photocatalytic Nitrogen Fixation.

Exploiting cost-effective, high-efficiency, and contamination-free semiconductors for photocatalytic nitrogen reduction reaction (N2 RR) is still a great challenge, especially in sacrificial-free system. On basis of the electron "acceptance-donation" concept, a boron-doped and carbon-deficient g-C3 N4 (Bx CvN)isherein developed through precise dopant and defect engineering. The optimized B15 CvN exhibisted an NH3 production rate of 135.3µmolh-1 g-1 in pure water with nine-fold enhancement to the pristine graphitic carbon nitride (g-C3 N4 ), on account of the markedly elevated visible-light harvesting, N2 activation, and multi-directional photoinduced carriers transfer. The decorated B atoms with coexistent occupied and empty sp3 hybridized orbitals are theoretically proved to be in charge of the increase of N2 adsorption energy from -0.08 to -0.26eV and the change in N2 adsorption model from one-way to two-way end-on pattern. Noticeably, the elaborate coordination of doped B atoms and carbon vacancies greatly facilitated the interlayer interaction and vertical charge migration of Bx CvN, whichisdistinctly revealed through the charge density difference calculations. The current study provides an alternative groundbreaking perspective for advancing photocatalytic N2 RR through the targeted configuration of the defect and dopant sites.

Synergistic Effect between CO2 Chemisorption Using Amino-Modified Carbon Nitride and Epoxide Activation by High-Energy Electrons for Plasmon-Assisted Synthesis of Cyclic Carbonates.

Photocatalytic CO2 cycloaddition is a promising approach for CO2 value-added processes. However, the efficiency of plasmon-assisted CO2 cycloaddition still needs to be improved and the reaction mechanism is unclear. Herein, g-C3N4/Ag (ACN-Ag) hybrids exhibited superior activity of CO2 cycloaddition by coupling a semiconductor into the plasmonic system, in which the ACN grafting amino group by the formation of carbon vacancies can enhance CO2 chemisorption; meanwhile, photo-generated electrons from ACN transfer to Ag to form high-energy electrons, which can activate propylene oxide, accelerating the ring-opening step. Importantly, photo-generated electron injection from ACN to Ag and the interaction between Ag nanoparticles and ACN were confirmed by single-particle photoluminescence spectroscopy. The wavelength-dependent activity demonstrated that the plasmon excitation is crucial for the reaction. Moreover, in situ single-particle PL quenching caused by propylene oxide and in situ electron paramagnetic resonance verified the activation of propylene oxide by ACN-Ag. This work is conducive to an in-depth understanding of the mechanism of CO2 cycloaddition at the single-particle level and provides guidance for the organic synthesis.

Electrodeposition of Pt-Ni nanoparticles on graphene as an electrocatalyst for oxygen reduction reaction.

Owing to its novel properties, such as high electrical conductivity and large specific surface area, graphene has been found as suitable support material for the electrocatalyst design. This work reports the preparation of platinum-nickel alloy nanoparticles (PtNi NPs) electrocatalyst by electrodeposition of PtNi NPs onto graphene support. The obtained PtNi/graphene electrocatalysts were characterized by high resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray microscopy (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) indicating the controllable morphological and compositional profiles of PtNi NPs on graphene. The electrocatalytic characteristics of PtNi/graphene toward oxygen reduction reaction (ORR) were systematically investigated showing comparable kinetic performance. Moreover, the graphene during electrodeposition process induces carbon vacancies and defects, increasing interaction between nanoparticles and graphene and enhancing electrocatalytic stability by limiting aggregation of the nanoparticles during accelerated stability test. This work opens a promising path for the preparation of graphene-supported alloy electrocatalyst.

In-Gap States of HfO2 Nanoislands Driven by Crystal Nucleation: Implications for Resistive Random-Access Memory Devices

Envisioned extremely scaled, high-performance memory devices request to conduct the step from thin semiconductor films to nanoscale structures and the use of promising high-k materials such as hafnium oxide (HfO2). HfO2 is well suited for use in resistive random-access memory (ReRAM) devices based on the valence change mechanism. Here, we provide a decidedly scaled system, namely, HfO2 nanoislands that are grown by van der Waals epitaxy on highly oriented pyrolytic graphite (HOPG). The electronic and structural properties of these well-separated, crystalline HfO2 nanoislands are investigated by scanning probe methods as well as ab initio methods. The topography reveals homogeneously formed HfO2 nanoislands with areas down to 7 nm2 and a thickness of one unit cell. They exhibit several acceptor- and donor-like in-gap states in addition to the bulk band gap, implying bulk properties. X-ray photoelectron spectroscopy indicates hafnium carbide formation as one possible origin for defect states. Going further to the crystal nucleation of HfO2, nanocrystals with a diameter of 2.7–4.5 Å are identified next to carbon vacancies in the topmost HOPG layer, indicating that carbon is incorporated into the islands at early nucleation stages. A precise description of these nuclei is accomplished by the simulation of small HfmOn(:C) clusters (m = 3 to 10; n = 3 to 22) with and without carbon incorporation using ab initio methods. The comparison of the theoretically determined lowest-energy clusters and electronic states with the experimental results allows us to identify the structure of the most relevant HfO2 sub-nanometer crystals formed during the first nucleation steps and the nature of the in-gap states found at the surfaces of HfO2 nanoislands. That way, a model system is derived that consists of distinct structural units, related to surface states or defect states, respectively, that will promote the tailoring of in-gap states of smallest HfO2 structures and thus the scalability of memory devices.

Effect of hydrogen on the unintentional doping of 4H silicon carbide

High-purity semi-insulating (HPSI) 4H silicon carbide (4H-SiC) single crystals are critical semiconductor materials for fabricating GaN-based high-frequency devices. One of the major challenges for the growth of HPSI 4H-SiC single crystals is the unintentional doping of nitrogen (N) and boron (B). The addition of hydrogen has been supposed to mitigate unintentional doping. However, the underlying mechanism has not been well understood. In this work, the role of hydrogen in the growth of HPSI 4H-SiC single crystals is investigated by first-principles formation-energy calculations. We find that the addition of hydrogen significantly mitigates N doping while hardly affecting B doping. Once hydrogen is added, hydrogen may adsorb at the growing surface of 4H-SiC, leading to surface passivation. Since N can react with hydrogen to form stable NH3 (g), the chemical potential of N is reduced, so that the formation energy of N in 4H-SiC increases. Hence, the critical partial pressure of nitrogen required for the growth of HPSI 4H-SiC single crystals increases by two orders of magnitude. Moreover, we reveal that the adjustment of relative B and N doping concentrations has a substantial impact on the Fermi energy of HPSI 4H-SiC. When the doping concentration of N is higher than that of B, N interacts with carbon vacancies (VC) to pin the Fermi energy at Z1/2. When the doping concentration of B is higher than that of N, the Fermi energy is pinned at EH6/7. This explains that the resistivity of unintentionally doped HPSI 4H-SiC may vary.

Theoretical study of CO adsorption and activation on h-Fe7C3[formula omitted] for Fischer-Tropsch synthesis

The h-Fe7C3 phase of iron carbide catalysts have been gained wide attentions for the impressive intrinsic activity in typical medium-temperature Fischer-Tropsch synthesis (FTS). In this study, the adsorption and activation of CO on h-Fe7C3(11¯1) surface were studied by density functional theory (DFT) calculations to understand the FTS mechanism. Calculated results showed that the B5 site on h-Fe7C3(11¯1) surface demonstrates excellent intrinsic activity for CO adsorption and activation. The route CO+H—HCO—CH+O—CH2+O is identified as a preferred CO activation pathway on the B5 site for h-Fe7C3(11¯1) surface with the effective energy barrier of 1.380 eV. Furthermore, the FTS reaction mechanism with the surface carbon atoms involved was explored preliminarily, which confirms that the surface carbons can undergo hydrogenation reaction to produce the CH species feasibly, and meanwhile, the carbon vacant sites are generated. Subsequently, the influences of carbon vacancy on the CO adsorption and activation on (11¯1) were studied. It was observed that the vacancy surface is more conducive to the elementary reactions of CO adsorbed on the B5 site. In particular, CO can be easily dissociated on the VC2 surface with energy barrier of 0.77 eV.

Theoretical Study of Oxygen Reduction Reaction Mechanism in Metal-Free Carbon Materials: Defects, Structural Flexibility, and Chemical Reaction.

Metal-free carbon materials are attractive Pt-based catalyst alternatives. However, despite efforts, the reaction mechanism remains elusive. Thus, we investigated the role of defects (dopant nitrogen and carbon vacancy) on the catalytic oxygen reduction reaction in a metal-free carbon material focusing on the effect of structural flexibility. Crucially, defects lower the energy barrier for the sp2/sp3 transition of the carbon-centered O2-adsorption sites by releasing structural strain during the reaction. In particular, low-coordinated pyridinic-N displaces from the carbon plane to release the strain, whereas weak C-C bonds around the carbon vacancy change the bond lengths to release the strain. Defects indirectly promote the adsorption of oxygen by enhancing structural flexibility. Thus, the nonlocal structural environment is as critical as the direct interaction between adsorption sites and adsorbate in the chemical reaction. Molecular dynamics simulations reveal that pyridinic-N doping is a facile route to introduce stable catalytic active sites. Overall, our results provide a deeper understanding of chemical processes on defective carbon materials.

Photocatalytic reduction performance and mechanisms of Cr(VI) by illite-g-C3N4 under visible light

Cr(VI) has great solubility and mobility in water, and is a class of highly toxic heavy metals. Illite modified g-C3N4 (IL-CN) materials were successfully synthesized and their photocatalytic activities for Cr(VI) reduction under visible light irradiation were tested in this study. Due to carbon and oxygen vacancies and defects by IL-CN, the modified IL-CN materials exhibited larger specific surface area and pore volume, and stronger electron-hole pair separation capacities. As a result, the IL-CN catalysts exhibited excellent catalytic activity for Cr(VI) reduction. Approximately 91.8 % of Cr(VI) was reduced to Cr(III) after 60 min of treatment under photocatalytic reaction of 2/IL-CN, which was much higher than those of the single g-C3N4 and single illite materials. There existed an optimum ratio of illite/g-C3N4 to realize the greatest Cr(VI) reduction efficiency. Acidic conditions and relatively higher dosage of IL-CN were conducive to Cr(VI) reduction. Cr(VI) reduction was mainly initiated by free electron in the photocatalytic system of modified IL-CN materials, while the role of O2− was quiet weak. Furthermore, the stability and recycling of the IL-CN catalysts were evaluated.

Rich carbon vacancies facilitated solar light-driven photocatalytic hydrogen generation over g-C3N4 treated in H2 atmosphere

Graphite carbon nitride (g-C3N4) has caught far-ranging concern for its masses of advantages, for instance, the unique graphite-like two-dimensional lamellar structure, low cost, nontoxic, suitable bandgap of 2.7 eV and favorable stability. Whereas owing to the shortcomings of low solar absorptivity and fast recombination of photo-induced charge pairs, the overall quantum efficiency of photocatalysis for g-C3N4 is suboptimal, resulting in limited practicality of g-C3N4 (GCN). In our study, modified g-C3N4 materials (HCN) with ample carbon vacancies (CVs) were obtained through calcinating of g-C3N4 in H2 atmosphere. Higher specific surface area and more active sites of HCN were induced by roasting of g-C3N4 in H2. CVs that occurred in the N-(C3) bond lead to the reduction of electron density around N, thus narrowing the bandgap of HCN-3h and enlarging corresponding light response capability. Under the synergistic function of abundant pore construction and CVs on HCN, the photo-excited e−/h+ pairs can be memorably separated and transferred, which is favorable to photocatalytic efficiency. Among HCN, the HCN-3h sample has the highest H2 generation rate of 4297.9 μmol h−1 g−1, which achieves 2.3-fold higher than that of GCN (1291.7 μmol h−1 g−1). This paper brings forward a meaningful method of boosting the photocatalytic performance of photocatalysts by constructing abundant CVs.

Scrutinizing the role of tunable carbon vacancies in g-C3N4 nanosheets for efficient sonophotocatalytic degradation of Tetracycline in diverse water matrices: Experimental study and theoretical calculation

Metal-free polymeric graphitic carbon nitride (CN) materials are robust and stable visible-light-driven photocatalysts that have recently piqued interest in photocatalytic applications. Its photocatalytic performance is restricted remarkably due to moderate oxidation ability and fast charge carrier recombination rate. To address these issues, we engineered carbon-vacant CN (FCN) using a facile formalin-assisted thermal polymerization of molten CN precursor in which the carbon vacancies (Cv) were regulated by altering formalin dosage. Consequently, FCN catalysts revealed Cv concentration-dependent sonophotocatalytic degradation of Tetracycline (TC) antibiotics over diverse water matrices. The optimal FCN exhibited complete TC degradation efficiency within 60 min with a synergy index of 1.4, which is approximately 2.6 times higher than that of pristine CN. The enhanced sonophotocatalytic performance was mainly due to the synergistic effect of ultrasound and light irradiation. The Cv formation also resulted in enhanced charge carrier transportation and facilitated oxygen adsorption at the Cv site of FCN - supported by both experimental study and theoretical calculation. Subsequently, FCN generated abundant reactive active oxygen species including, •O2–, as well as indirectly •OH which played a significant role in the degradation pathway and mineralisation of the TC molecules. This study provides insight into understanding the correlation between controllable defects and sonophotocatalytic degradation properties of the self-doped and deficient FCN.

Vacancy Hardening and Ordering in Rhenium Tungsten Carbides

Vacancies generally reduce the number of chemical bonds and hence cause structural softening. It is puzzling, however, that substoichiometric Re0.5W0.5C0.4 with 60% carbon vacancies was identified as a superhard material. Here, we report the underlying mechanism responsible for such anomalous vacancy-induced hardening in the Re0.5W0.5C1–x system via first-principles calculations. The shear stiffness and hardness increase consistently with rising carbon vacancy concentration in Re0.5W0.5C1–x and reach the maximum at about x = 40%. Such an unexpected hardening phenomenon originates from a gradual relief of the shear-unstable dd bonding and unfavorable pd antibonding interactions owing to the formation of C-vacancies. We further predict that the simultaneous ordered vacancies of W and C atoms can produce a cubic crystalline Re2/3W1/3C that is isomorphic with the NbO type. The calculations on vibrational, mechanical, and electronic properties reveal that this phase has considerable structural stability and is a hard metallic material. This work not only elucidates the intriguing mechanism responsible for the vacancy hardening in this class of systems but also provides a new principle for the structural stability of other transition-metal compounds.

Carbon vacancies enriched carbon nitride nanotubes for Pd coordination environment optimization: Highly efficient photocatalytic hydrodechlorination and CO2 cycloaddition

The use of easily available solar energy to achieve pollutants efficient degradation and waste carbon resource CO2 utilization under mild conditions is highly desired. Herein, novel carbon vacancies enriched nanotubes graphitic carbon nitride (SCNT-500) has been successfully fabricated via melamine (MA) supramolecular hydrogen-bonded self-assembly in the presence of H2SO4. Pd NPs loaded carbon vacancies enriched carbon nitride nanotubes (Pd/SCNT-500) were used for photocatalytic chlorophenols hydrodechlorination and CO2 cycloaddition with styrene oxide. Up to 6.93 s-1 4-chlorophenol hydrodechlorination TOF and obviously improved CO2 cycloaddition efficiency could be realized with Pd/SCNT-500. The improved photocatalytic efficiency should be related to the morphology and carbon vacancies based Pd coordination environment optimization. Such as, the surface area increased nanotubes structure promoted light harvesting along with photoelectrons and holes generation; the carbon vacancies improved excited electrons capture, photoinduced carriers recombination inhibition along with substrates adsorption with electron rich Pd NPs. Mechanism studies not only demonstrated the important role of atomic hydrogen and Pd coordination environment optimization in the chlorophenols hydrodechlorination, but also confirmed the promotion ability of photogenerated electrons on CO2 cycloaddition.

Adsorption of formaldehyde on titanium decorated graphene

This work presents results for the adsorption of the formaldehyde molecule on one Ti-graphene layer formed by 32 carbon atoms. Calculations are done under the DFT (density functional theory) scope as implemented in Quantum espresso computer code. After the equilibrium Ti position above a pristine graphene layer has been obtained, it is added the CH2O molecule to obtain the equilibrium configuration of the entire system. Previously also the equilibrium configuration of the formaldehyde molecule and the graphene layer was obtained. Ti atom makes bonds with both, carbon and oxygen atom of the formaldehyde molecule. Adsorption of CH2O molecule above graphene and Ti-graphene with one and two carbon vacancies is discussed.

Enhanced Electrochemiluminescence of Graphitic Carbon Nitride by Adjustment of Carbon Vacancy for Supersensitive Detection of MicroRNA.

Herein, a supersensitive biosensor was constructed by using graphitic carbon nitride with a carbon vacancy (VC-g-C3N4) as an efficient electrochemiluminescence (ECL) emitter for detection of microRNA-21 (miRNA-21). Impressively, VC-g-C3N4 could be prepared by formaldehyde (HCHO)-assisted urea ploycondensation, and the concentration of the carbon vacancy could be controlled by adjusting the dosage of HCHO to improve the ECL performance, in which the carbon vacancy could improve the charge carrier transfer to enhance the conductivity and it also could be used as an electron trap to prevent electrode passivation and facilitate the adsorption of coreactant S2O82- to accelerate its reduction. Compared with original g-C3N4, the introduction of carbon vacancies resulted in a significant enhancement of the ECL efficiency of VC-g-C3N4. With the aid of improved cascade strand displacement amplification (IC-SDA), the ECL biosensor realized sensitive detection of miRNA-21 with a low detection limit of 3.34 aM. This successful strategy promoted the development of g-C3N4 in the ECL field to construct the sensitive biosensor for molecular and disease diagnoses.

Investigating the Role of Surface Roughness and Defects on EC Breakdown, as a Precursor to SEI Formation in Hard Carbon Sodium-Ion Battery Anodes.

Hard carbon (HC) anodes together with ethylene carbonate (EC)-based electrolytes have shown significant promise for high-performing sodium-ion batteries. However, questions remain in relation to the initial contact between the carbon surface and the EC molecules. The surface of the HC anode is complex and can contain both flat pristine carbon surfaces, curvature, nanoscale roughness, and heteroatom defects. Combining density functional theory and experiments, the effect of different carbon surface motifs and defects on EC adsorption are probed, concluding that EC itself does not block any sodium storage sites. Nevertheless, the EC breakdown products do show strong adsorption on the same carbon surface motifs, indicating that the carbon surface defect sites can become occupied by the EC breakdown products, leading to competition between the sodium and EC fragments. Furthermore, it is shown that the EC fragments can react with a carbon vacancy or oxygen defect to give rise to CO2 formation and further oxygen functionalization of the carbon surface. Experimental characterization of two HC materials with different microstructure and defect concentrations further confirms that a significant concentration of oxygen-containing defects and disorder leads to a thicker solid electrolyte interphase, highlighting the significant effect of atomic-scale carbon structure on EC interaction.

Regulating the Electronic Configuration of Spinel Zinc Manganate Derived from Metal-Organic Frameworks: Controlled Synthesis and Application in Anode Materials for Lithium-Ion Batteries.

In recent years, transition metal oxides have been considered as the most promising anode materials due to their high theoretical capacity, low price, and abundant natural reserves. Among them, zinc manganate is used as an electrode material for anodes, whose application is mostly hindered due to its poor ionic/electronic conductivity. In this work, a series of ZnMn2O4 (ZMO) are synthesized by a hydrothermal technique coordinated with a metal-organic framework-based high-temperature calcination process for their application as an anode in lithium-ion batteries (LIBs). Meanwhile, this study systematically explores the influence of carbon doping and the types of organic ligands and oxygen vacancies on the electrochemical properties of the synthesized ZMO. Density functional theory (DFT) calculations and experimental investigations reveal that the introduction of carbon and oxygen vacancies can enhance electronic conductivity, more active sites and faster Li+ adsorption, resulting in better electrochemical performances. As expected, all ZMOs with carbon doping (PMA-ZMO, MI-ZMO, and BDC-ZMO) derived from 1,2,4,5-benzenetetracarboxylic acid, 2-methylimidazole, and 1,4-dicarboxybenzene achieve outstanding electrochemical performance. Meanwhile, the introduction of oxygen vacancies can enhance the electronic conductivity and can significantly reduce the activation energy of Li+ transport, thereby accelerating the Li+ diffusion kinetics in the lithiation/delithiation process. Furthermore, an optimal ZMO anode material synthesized by 2-methylimidazole delivers a high reversible capacity of 1174.7 mA h g-1 after 300 cycles at 0.1 A g-1 and 600 mA h g-1 at 0.5 A g-1 after 300 cycles. After high-rate charge and discharge cycles, the specific capacity rapidly recovers to a value greater than the initial value, which proves the unusual activation and thereby an excellent rate property of the electrode. Hence, we conclude that ZMO provides potential application prospects as an anode electrode material for LIBs.

Synthesis of vacant graphitic carbon nitride in argon atmosphere and its utilization for photocatalytic hydrogen generation

Graphitic carbon nitride (C3N4) was synthesised from melamine at 550 °C for 4 h in the argon atmosphere and then was reheated for 1–3 h at 500 °C in argon. Two band gaps of 2.04 eV and 2.47 eV were observed in all the synthetized materials. Based on the results of elemental and photoluminescence analyses, the lower band gap was found to be caused by the formation of vacancies. Specific surface areas of the synthetized materials were 15–18 m2g−1 indicating that no thermal exfoliation occurred. The photocatalytic activity of these materials was tested for hydrogen generation. The best photocatalyst showed 3 times higher performance (1547 μmol/g) than bulk C3N4 synthetized in the air (547 μmol/g). This higher activity was explained by the presence of carbon (VC) and nitrogen (VN) vacancies grouped in their big complexes 2VC + 2VN (observed by positron annihilation spectroscopy). The effect of an inert gas on the synthesis of C3N4 was demonstrated using Graham´s law of ammonia diffusion. This study showed that the synthesis of C3N4 from nitrogen-rich precursors in the argon atmosphere led to the formation of vacancy complexes beneficial for hydrogen generation, which was not referred so far.

Ultrathin nitrogen-doped defective carbon layer embedded with NiFe for solid zinc-air batteries

Developing a simple oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) bifunctional catalyst construction strategy for zinc-air batteries (ZABs) has been a major challenge. Therefore, this study synthesized an ultrathin nitrogen-doped defective carbon layer embedded with nickel-iron (NiFe) (ZGNiFe@NG) by introducing zinc gluconate to the precursor. In situ generated NiFe nanoparticles facilitated the OER catalyzation kinetics process, nitrogen-doped graphene demonstrated a large specific surface area, providing more active sites to boost electron transfer and mechanical support for the NiFe nanoparticles. Additionally, the introduction of Zn ions can enrich carbon vacancies in the structure of composite catalyst, which is beneficial to the further improvement of catalytic activity. The investigations revealed that the obtained ZGNiFe@NG catalyst possessed a higher ORR half-wave potential of 0.81 V and a lower OER potential of 1.65 V of 10 mA cm−2, presenting a bifunctional catalytic activity toward ORR and OER than that of catalysts lacking the Zn ion precursor. Moreover, as expected, the fabricated solid-state flexible ZAB with ZGNiFe@NG catalyst delivered a high power density of 84.95 mW cm−2 at a current density of 112 mA cm−2 and could operate 65 h steadily. In summary, this work paves a way for designing a carbon matrix with dopants and defects to load NiFe nanoparticles as superior cathode materials of ZABs.