Bifunctional Catalytic Activity Research Articles

Theoretical regulating the M-site composition of Janus MXenes enables the tailoring design for highly active bifunctional ORR/OER catalysts

Rechargeable metal-air batteries generally require efficient, durable, and safe bifunctional electrocatalysts to simultaneously support oxygen reduction/evolution reactions (ORR/OER). Herein, we employed first-principles calculations to explore the structure-activity relationship between the composition control of metal atoms and the catalytic activity of Pt-doped Ti2–xMnxCO2 single-atom catalysts (SACs). The research found a clear linear relationship between the proportion of Mn and bifunctional performance, which can effectively modulate catalytic activity. Additionally, it shows excellent bifunctional catalytic activity at medium concentrations, among which the catalyst of Pt-VO-Ti0.89Mn1.11CO2 displays the lowest overpotential (ηORR/OER = 0.26/0.28 V). Attributed to the modulation of the average magnetism of Mn and the d-band center of Pt by different components, the bonding strength of the active center of Pt to adsorption intermediates is changed, resulting in the enhancement of the catalyst activity. Crucially, the molecular orbital-level bonding between the active site Pt and the adsorbed intermediate OH is clarified, shedding light on the involvement of the partially occupied antibonding state of Pt's d orbital in the activation process. The research extensively explores the control of catalyst activity through composition, offering strong support for designing and optimizing highly active Janus MXene-supported SACs.

Construction of Co3S4/MoS2 p-p heterojunction as an efficient catalyst for water splitting and electrochemical oxidation of organic molecules

Electrolysis of wastewater containing urea or small organic molecules while obtaining hydrogen energy is a promising strategy for realizing energy acquisition and environmental protection. Construction of semiconductor heterojunctions to regulate the transfer of interfacial electrons has been regarded as an efficient approach to improve the electrocatalytic performance of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) for the materials, and obtain the bifunctional electrocatalysts aiming to construct a water splitting cell using one non-precious metal material. Herein, a bifunctional Co3S4/MoS2 electrocatalyst with a p-p heterojunction and hollow structure has been successfully prepared through the precipitation-hydrothermal method, which presents the high bifunctional electrocatalytic performance due to the formed path of electron transfer in the heterojunction interface being favorable for OH- adsorption. The accelerated electron transfer in heterojunction interfaces endows Co3S4/MoS2 presenting the superior electrocatalytic performance including OER, urea oxidation reaction (UOR) and oxygen evolution reaction in lactic acid solution (OER-LA). At 50 mA cm−2, the voltages of HER, OER, UOR and OER-LA are −0.123, 1.511, 1.400, 1.440 V vs. RHE, respectively. In a two-electrode electrolytic cell using Co3S4/MoS2 as anode and cathode displays the outstanding electrocatalytic performance in 1 M KOH, 1 M KOH containing 0.5 M urea, and 1 M KOH containing 0.5 M lactic acid electrolytes, superior to the most reported materials. This research provides a strategy for the construction of advanced bifunctional electrocatalysts using metal sulfides to form heterojunction for realizing the high bifunctional catalytic activities in hydrogen production and organic molecule decontamination.

Synthesis of nickel phosphate nanowires as a bifunctional catalyst for water electrolysis in alkaline media

The electrocatalytic water splitting (WS) process for hydrogen (H2) and oxygen (O2) production is known for its high efficiency, necessitating the development of bifunctional electrode materials. These materials must possess strong catalytic activity, significant active sites, high stability, and an abundance of earth-friendly components to ensure efficient and prolonged H2 and O2 generation. In this study, we employed a hydrothermal method to synthesize unique one-dimensional (1D) nickel phosphate (NiPO) nanoneedles directly grown on nickel foam (NF). The in-situ synthesis of the NiPO/NF catalyst offers favorable streamlining, facilitating electrode production and improving the contact between active sites and the conductive substrate. Under alkaline conditions, the NiPO/NF electrodes demonstrated low overpotentials of 374 mV and 377 mV at a high current density (J) of 250 mAcm−2 for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. These values indicate efficient and stable electrocatalytic activity. Moreover, the NiPO/NF catalyst exhibited continuous bifunctional catalytic activity for 12 hours with a J exceeding 20 mAcm−2. These findings suggest that NiPO/NF has the potential to be a cost-effective and sustainable option for large-scale WS applications.

Synergistic Effect of Trimetallic PdCuIn Nanoparticles in Ethanol and Formate Oxidation Reaction for Remarkable Catalytic Performance

Direct liquid fuel cells (DLFC) are regarded as attractive energy devices with their advantages of sustainability and eco‐friendly operation. Pd‐based materials have been recognized as ideal catalysts for anodic oxidation of DLFC. Although reasonably regulating the structure of Pd‐based catalysts to achieve remarkable catalytic performance, it is not clear about the combined effects of d‐band center and charge transfer, which are the crucial impactors for catalytic activity. Herein, a facile method to synthesize trimetallic PdCuIn nanoparticles (PdCuIn NPs) for ethanol and formate oxidation reactions (EOR and FOR, respectively) is reported. PdCuIn NPs exhibits bifunctional catalytic activities for both EOR and FOR, with mass activities of 16 000 and 15 500 mA mgPd−1, respectively, which are much better than those of commercial Pd/C catalysts. Comparing to the bimetallic nanoparticles (PdCu or PdIn NPs), additional Cu or In enhances the electron transfer and achieves a suitable d‐band center, resulting in excellent performance. This work synthesizes a highly active catalyst for both EOR and FOR, but also provides facile strategy of balancing the d‐band center and charge transfer for high catalytic performance.

Ni-Co ternary nitrides with multiple surface oxides as bifunctional oxygen electrocatalysts for metal-air batteries

The bifunctional non-noble metal catalysts based on the metal nitrides with high activity and high efficiency is very challenging for the development of high-performance metal-air batteries. Herein, a new Ni-Co ternary nitrides anchored on nitrogen-doped carbontubes (denoted as NiCoxN/CNT) is rationally designed by the thermal of corresponding hydroxide/carbontubes at low temperature, following nitridation. The synergistic effect between Ni-Co ternary nitrides (Ni4N, Co5.47N, CoN) effectively regulates the electronic configuration of the active site, thereby optimizing the chemisorption energy of the reaction intermediates, resulting in improved intrinsic catalytic activity. The result shows that NiCoxN/CNT not only exhibits excellent half-wave potential of 0.80 V for ORR but also with a low overpotential of 280 mV for OER at 10 mA cm−2, outperforming those of cobalt mononitride and nickel mononitride. Furthermore, Zn-air batteries assembled with NiCoxN/CNT show a high specific capacity of 826.9 mA h g−1 and excellent cycling stabilities up to 190 h in an aqueous electrolyte. More attractively, when assembled into Mg-air batteries, NiCoxN/CNT cathode realizes high power density of 112.38 mWcm−2. Therefore, the design and construction of multiple TMNs is a new guide to break through the bifunctional catalytic activity.

Revolutionizing Zn-Air batteries with chainmail catalysts: Ultrathin carbon-encapsulated FeNi alloys on N-doped graphene for enhanced oxygen electrocatalysis

The sluggish kinetics of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) pose significant challenges for the viability of rechargeable Zn-air batteries. Developing efficient, cost-effective, stable, and dual-purpose oxygen electrocatalysts remains a formidable hurdle. In this study, we successfully synthesized a highly promising chainmail catalyst named FeNi@NC, comprising ultrathin carbon shells encapsulating FeNi alloy nanoparticles on N-doped graphene-like nanosheets. The strong synergistic effects between FeNi alloys and N-doped carbon shells result in outstanding bifunctional catalytic activity, particularly in alkaline media. Consequently, Zn-air batteries incorporating FeNi@NC as the catalyst demonstrate exceptional performance, operating reliably at high power density with extended lifespan. Furthermore, computational analyses provided further confirmation of the catalytic activity and revealed that the electron transfer from FeNi alloy nanoparticles to the carbon shells activates the carbon surface, leading to enhanced catalytic performance. This research not only sheds light on the rational design and synthesis of heteroatom-doped carbon materials supporting the growth-constrained transition metal alloys but also offers a practical solution for advancing the application of Zn-air batteries.

Architecting N-doped Carbon Nanotube-Rich Carbon Nanofibers with Biomimetic Vine-Leaf-Whisker Structure as Robust Bifunctional Electrocatalysts for Rechargeable Zn-Air Batteries.

Efficient and durable bifunctional catalysts toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are urgently desirable but challenging for rechargeable Zn-air batteries (ZABs), especially flexible wearable ZABs. Inspired by the vine-leaf-whisker structure in nature, we proposed a three-dimensional (3D) hierarchical bifunctional catalyst (denoted as Co-Fe-Zn@N-CNT/CNF) consisting of N-doped carbon nanotubes embedded with abundant CoFe alloy nanoparticles, leaf-shaped N-doped carbon nanoflakes, and porous carbon fibers for rechargeable ZABs. The special biomimetic structure provides a large specific surface area, allowing for high exposure of the active site and ensuring fast mass transport/charge transfer. The close combination of CoFe bimetallic alloys and N-doped carbon nanotubes delivers high electrocatalytic activity, while the coexistence of various active sites such as metal nanoparticles (NPs), metal-Nx, doped N species, and their synergistic interactions endows the catalysts with more active sites. As such, the Co-Fe-Zn@N-CNT/CNF catalyst achieves superior bifunctional catalytic activities for the ORR (a half-wave potential of 0.84 V) and the OER (an overpotential of 326 mV at 10 mA cm-2) in alkaline media, comparable to commercial Pt/C and RuO2. Remarkably, both aqueous and solid-state ZABs assembled with Co-Fe-Zn@N-CNT/CNF catalysts as air electrodes demonstrate excellent charging/discharging performance, high peak power density, and robust long-term cycling stability. More interestingly, the flexible ZAB performs well even under bending conditions, displaying satisfactory device stability and mechanical flexibility. This study presents a new collective morphological-composition-structural engineering strategy for exploiting the efficient bifunctional oxygen electrocatalysts, which is of great significance for high-performance rechargeable ZABs and wearable energy storage devices.

Simultaneous Efficient Photocatalytic Hydrogen Evolution and Degradation of Dye Wastewater without Cocatalysts and Sacrificial Agents Based on g-C3N5 and Hybridized Ni-MOF Derivative-CdS-DETA.

Inspired by energy conversion and waste reuse, hybridized Ni-MOF derivative-CdS-DETA/g-C3N5, a type-II heterojunction photocatalyst, is synthesized by a hydrothermal method for simultaneous and highly efficient photocatalytic degradation and hydrogen evolution in dye wastewater. Without the addition of cocatalysts and sacrificial agents, the optimal MOF-CD(2)/CN5 (i.e. Ni-MOF derivative-CdS-DETA (20 wt.%)/g-C3N5) exhibit good bifunctional catalytic activity, with a H2 evolution rate of 2974.4µmolg-1h-1 during the degradation of rhodamine B (RhB), and a removal rate of 99.97% for RhB. In the process of H2-evolution-only, triethanolamine is used as a sacrificial agent, exhibiting a high H2 evolution rate (19663.1µmolg-1h-1) in the absence of a cocatalyst, and outperforming most similar related materials (such as MOF/g-C3N5, MOF-CdS, CdS/g-C3N5). With the help of type-II heterojunction, holes are scavenged for the oxidative degradation of RhB, and electrons are used in the decomposition of water for H2 evolution during illumination. This work opens a new path for photocatalysts with dual functions of simultaneous efficient degradation and hydrogen evolution.

Engineering Co-N-Cr Cross-Interfacial Electron Bridges to Break Activity-Stability Trade-Off for Superdurable Bifunctional Single Atom Oxygen Electrocatalysts.

Atomically dispersed metal-nitrogen-carbon (M-N-C) catalysts have exhibited encouraging oxygen reduction reaction (ORR) activity. Nevertheless, the insufficient long-term stability remains a widespread concern owing to the inevitable 2-electron byproducts, H2O2. Here, we construct Co-N-Cr cross-interfacial electron bridges (CIEBs) via the interfacial electronic coupling between Cr2O3 and Co-N-C, breaking the activity-stability trade-off. The partially occupied Cr 3d-orbitals of Co-N-Cr CIEBs induce the electron rearrangement of CoN4 sites, lowering the Co-OOH* antibonding orbital occupancy and accelerating the adsorption of intermediates. Consequently, the Co-N-Cr CIEBs suppress the two-electron ORR process and approach the apex of Sabatier volcano plot for four-electron pathway simultaneously. As a proof-of-concept, the Co-N-Cr CIEBs is synthesized by the molten salt template method, exhibiting dominant 4-electron selectively and extremely low H2O2 yield confirmed by Damjanovic kinetic analysis. The Co-N-Cr CIEBs demonstrates impressive bifunctional oxygen catalytic activity (▵E=0.70 V) and breakthrough durability including 100 % current retention after 10 h continuous operation and cycling performance over 1500 h for Zn-air battery. The hybrid interfacial configuration and the understanding of the electronic coupling mechanism reported here could shed new light on the design of superdurable M-N-C catalysts.

Constructing highly efficient bifunctional catalysts for oxygen reduction and oxygen evolution by modifying MXene with transition metal

Exploring highly active electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) has become a growing interest in recent years. Herein, an efficient pathway for designing MXene-based ORR/OER catalysts is proposed. It involves introducing non-noble metals into Vo (vacancy site), H1 and H2 (the hollow sites on top of C and the metal atom, respectively) sites on M2CO2 surfaces, named TM-VO/H1/H2-M2CO2 (TM = Fe, Co, Ni, M = V, Nb, Ta). Among these recombination catalysts, Co-H1-V2CO2 and Ni-H1-V2CO2 exhibit the most promising ORR catalytic activities, with low overpotential values of 0.35 and 0.37 V, respectively. Similarly, Fe-H1-V2CO2, Co-VO-Nb2CO2, and Ni-H2-Nb2CO2 possess low OER overpotential values of 0.29, 0.39, and 0.44 V, respectively, suggesting they have enormous potential as effective catalysts for OER. Notably, Co-H2-Ta2CO2 possesses the lowest potential gap value of 0.53 V, demonstrating it has an extraordinary bifunctional catalytic activity. The excellent catalytic performance of these recombination catalysts can be elucidated through an electronic structure analysis, which primarily relies on the electron-donating capacity and synergistic effects between transition metals and sub-metals. These results provide theoretical guidance for designing new ORR and OER catalysts using 2D MXene materials.

Pre-implanting metal oxides to endow the N-doped carbon with boosted bifunctional catalytic activities towards oxygen reduction and oxygen evolution reactions

Nitrogen-doped carbon-based materials exhibit promising prospect as the catalysts to oxygen reduction reaction (ORR). Incorporating transition metal oxides with the catalysts can endow them with oxygen evolution reaction (OER) activity to construct bifunctional catalysts for rechargeable zinc-air batteries. In this work, a catalyst (named as 300NiFe-Mi-C) was prepared by a metal oxide-implanting strategy. The mixed metal salts of Ni and Fe were first heated to produce metal oxides, and then blended with 2-methylimidazole and carbon black, and subsequently pyrolyzed at a high temperature. In the pyrolysis, a part of metal oxides was reduced to metallic state to facilitate the doping of nitrogen atoms into carbon to form the ORR active sites while a part of metal oxides was retained to afford OER activity. Benefiting from the pre-implanting strategy of metal oxides, the resultant 300NiFe-Mi-C presents enhanced OER performance with 1.56 V of OER potential at 10 mA cm−2, outperforming the 1.68 V of the controlled sample NiFe-Mi-C (without pre-implanting) and 1.70 V of RuO2. The 0.83 V of ORR half-wave potential of 300NiFe-Mi-C is also comparable to the 0.82 V of NiFe-Mi-C and 0.86 V of Pt/C, revealing satisfactory bifunctional catalytic activities. The rechargeable zinc-air battery equipped with 300NiFe-Mi-C can stably operate at ∼1.25 V with 10 mA cm−2, being higher than ∼1.21 V of Pt/C+RuO2. The battery also presents outstanding durability and rechargeability, demonstrating the bifunctional activities of 300NiFe-Mi-C can be realized in practical applications.

Bidirectional enhancement of Li2S redox reaction by NiSe2/CoSe2-rGO heterostructured bi-functional catalysts

The high activity barriers of Li2S nucleation and deposition limit the redox reaction kinetics of lithium polysulfides (LiPSs), meanwhile, the significant shuttle effect of LiPSs hampers the advancement of Li-S batteries (LSBs). In this work, a NiSe2/CoSe2-rGO (NiSe2/CoSe2-G) sulfur host with bifunctional catalytic activity was prepared through a hard template method. Electrochemical experiment results confirm that the combination of NiSe2 and CoSe2 not only facilitates the bidirectional catalytic function during charge and discharge processes, but also increases the active sites toward LiPSs adsorption. Simultaneously, the highly conductive rGO network enhances the electronic conductivity of NiSe2/CoSe2-G/S and provides convenience for loading NiSe2/CoSe2 catalysts. Benefitting from the exceptional catalytic-adsorption capability of NiSe2/CoSe2 and the presence of rGO, the NiSe2/CoSe2-G/S electrode exhibits excellent electrochemical properties. At 1C, it demonstrates a low capacity attenuation of 0.087 % per cycle during 500 cycles. The electrode can maintain a discharge capacity of 927 mAh/g at a sulfur loading of 3.3 mg cm−2. The bidirectional catalytic activity of NiSe2/CoSe2-G offers a prospective approach to expedite the redox reactions of active S, meanwhile, this work also offers an ideal approach for designing efficient S hosts for LSBs.

Preparation of Co-W-P-O/NF catalyst with crystalline-amorphous phase structure by electrodeposition and study on its water splitting properties

The development of renewable clean energy is imminent as global warming and environmental pollution become more serious issues today. Hydrogen energy has been widely studied as an ideal green energy source. Among several common hydrogen production methods, hydrogen production by electrolysis of water is considered an efficient, environmentally friendly, and sustainable hydrogen production strategy. Transition metal phosphates have outstanding electrocatalytic conductivity and high catalytic efficiency, thus exhibiting catalytic effects similar to noble metals. To further enhance the catalytic activity of the transition metal phosphates, in this paper, the cauliflower-like Co-W-P-O4/NF catalyst based on three-dimensional nickel foam was prepared by the method of element doping. The catalyst exhibited good bifunctional catalytic activity in alkaline solution. The prepared Co-W-P-O4/NF has a unique crystalline-amorphous phase structure with abundant active sites at the interface. In addition, W atoms can interact with Co atoms to co-optimise the electronic structure, enabling the Gibbs free energy of hydrogen adsorption (ΔGH*) to be close to 0, which is conducive to improving the performance of water electrolysis. To achieve a current density of 10 mA·cm−2, the Co-W-P-O4/NF required overpotentials of 42.1 mV for HER and 348.2 mV for OER in 1 M KOH solution, with the Tafel slopes being 48.0 and 83.6 mV·dec−1, respectively. When Co-W-P-O4/NF was used as both cathode and anode for water splitting, the two-electrode electrolyzer could achieve 10 mA·cm−2 with only 1.62 V, along with good stability.

Synergistic promotion of electrocatalytic activities and multilevel descriptors in nitrogen-doped graphene supported dual-atom catalysts for lithium-sulfur batteries

Lithium-sulfur battery (LSB) is emerging as one of the most promising candidates in energy storage systems, but its performance is greatly limited by the polysulfide shuttle and sluggish reaction kinetics. Here, we focus on 18 dual-atom catalysts (DACs) supported by nitrogen-doped graphene with three types of metal coordination environment, namely M1M2Nx (M1, M2 = Fe, Co, Ni and x = 6 or 8), for sulfur redox by using first-principles calculations. Our results show that most DACs exhibit enhanced anchoring capacity toward polysulfides and superior electrocatalytic activity via a synergistic effect between the bimetallic sites. Among them, FeNiN8 presents balanced bifunctional catalytic activities with reduced Gibbs free energy change during the conversion of Li2S4 to Li2S (1.091 eV) and decomposition barrier of Li2S (1.330 eV) to boost reaction kinetics during charge-discharge cycling, surpassing single-atom counterparts. In particular, multilevel descriptors correlating the target catalytic properties with adsorption energies of key sulfur species, ICOHP of M-S atom pairs, and the fundamental geometric and electronic properties are identified to characterize the catalytic activities of DACs. Extended DACs to other 3d transition metals further demonstrate the effective design strategy and their broad application prospects in LSBs, which contributes to a deep understanding of the origin of catalytic activity of dual-atom sites.

Fe doped Co9S8 nanoparticles embedded in N, S co-doped porous carbon as an efficient bifunctional electrocatalyst for rechargeable Zn-air batteries

Transition metal sulfides embedded in co-doped porous carbon materials with nitrogen and sulfur are a promising catalyst that can effectively solve the problem of slow oxygen reduction reaction (ORR) kinetics. However, monometallic sulfides consisting of a single active component only have monofunctional catalytic activity and cannot effectively increase the rate of oxygen evolution reaction (OER), thus limiting the energy conversion efficiency of Zn-air batteries (ZAB). Herein, a unique silica template assisted in situ pyrolysis strategy is used to synthesize iron (Fe)-doped cobalt sulfide (Co9S8) nanoparticle embedded in a honeycomb nitrogen (N), sulphur (S) co-doped porous carbon (Fe/Co9S8@NSC) electrocatalyst. The introduction of Fe increases the active component of the catalyst and further enhances the catalytic ability of Co9S8 by optimizing the electronic structure through charge transfer effect. Therefore, the rich active sites of Fe/Co9S8 nanoparticles anchored in N, S co-doped carbon materials with rich pore structure enable the catalysts to have good bifunctional catalytic activities of ORR and OER. In particular, the Fe/Co9S8@NSC has a high half-wave potential of 0.82 V for catalytic ORR and only needs low overpotential of 332 mV at a current density of 10 mA cm−2 for catalytic OER. In addition, the Fe/Co9S8@NSC catalyst based rechargeable ZAB also exhibits a significant specific capacity of 734 mAh g−1 and prolonged stability of 270 h, which outperforms the bulk of recently reported catalysts based on transition metal sulfides-based catalysts. This research offers a workable method for producing metal sulfides catalysts with bifunctional catalytic activity.

Electric field-induced phosphorization to prepare CoP@Biochar composites for efficient bifunctional oxygen electrocatalysis

An electric field-induction method was employed to construct an oxygen electrocatalyst (CoP@NWC). CoP@NWC exhibits excellent ORR/OER bifunctional catalytic activity (ΔE = 0.65 V) because of the multi-active site integration strategy.

Counter ion-regulated heterostructured Co@Fe-based core@shell materials: as remarkable bifunctional electrodes for green H2 production

The exceptional bifunctional catalytic activity of Co@Fe-based core@shell materials, when Co2P@Fe2P/NF was used as both the anode and cathode, achieving outstanding performance in alkaline water splitting, excelling in both the OER and the HER.

2D bifunctional tungsten disulfide-embedded UiO-66 (WS2@UiO-66) as a highly active electrocatalyst for water splitting

WS2 and UiO-66 hybrid as a highly effective electrocatalyst for water splitting. It shows improved bifunctional catalytic activity for both HER and OER for efficient overall water-splitting.

A hierarchical CoSx/Ni(OH)2 heterostructure as a bifunctional electrocatalyst for urea-assisted energy-efficient hydrogen production.

We report hierarchical CoSx/Ni(OH)2/NF heterostructure nanorod arrays, which manifest superior bifunctional catalytic activities for the HER and UOR due to amorphous Ni(OH)2, synergistic effect of multiple components and self-supported structure. The CoSx/Ni(OH)2/NF-based urea electrolyzer requires a low cell voltage of 1.485 V to deliver 10 mA cm-2, which is obviously lower than that needed in water electrolysis.

The regulatory function of the d-orbital structure in TM@g-t-C4N3 for bifunctional catalysis of the oxygen evolution/reduction reaction.

Highly efficient catalysts for the oxygen evolution/reduction reaction (OER/ORR) have attracted great attention in research for energy devices with high conversion efficiency. Herein, systematic first-principles investigations are performed to explore the catalytic performance of graphitic C4N3 loaded with single transition metal atoms (TM@g-t-C4N3) for the OER/ORR. The results show that Fe, Co, Ni and Rh@g-t-C4N3 exhibit fascinating bifunctional catalytic activities for both the OER and ORR. Moreover, it is observed that better activities are easily achieved when the valence d orbitals of doped TM atoms are nearly fully occupied. Further analysis reveals the volcano relationship between the OER/ORR performance and the adsorption Gibbs free energy. The adsorption free energy of intermediates in the OER/ORR process is also found to highly correlate with the electronic structures of TM@g-t-C4N3, which are mainly characterized by two quantities, one is the descriptor φ related to the electronegativity and the number of valence electrons in d orbitals, and the other is the projected d band center. The results indicate that it is possible to predict the catalytic performance of TM@g-t-C4N3 by a detailed examination of the electronic properties of the doped TM atoms to some extent. This research not only provides several highly active g-t-C4N3-based single-atom catalysts (SACs) for the OER/ORR, but also reveals some potential regularities of SAC systems.