Modulating single-atom M-N-C electrocatalysts for the oxygen reduction: the insights beyond the first coordination shell

Abstract

The oxygen reduction reaction (ORR) is a pivotal process in electrochemical energy systems such as fuel cells and metal-air batteries. Recent advancements have highlighted the single-atom metal-nitrogen-carbon (M-N-C) catalysts for their exceptional ORR electrocatalytic performance. However, further exploration is needed for the optimization methods of single atomic active sites. Significantly, the modulation of coordination environment emerges as a pivotal technique for the enhancement of M-N-C catalysts, while extending this modulation beyond the first coordination shell has ignited substantial investigation. This review delves into the frontier of M-N-C optimization by transcending the first coordination shell, presenting a comprehensive analysis of innovative strategies that modulate the electronic structure and reactivity of MN₄ sites. The primary focus lies in three regulation approaches: regulating atomic entities, introducing metallic species and tailoring non-metallic modulators. These strategies are scrutinized for their ability to fine-tune the ORR activity and stability at the atomic level. By providing a clearer trajectory for future research, this review should be able to inspire novel designs of high-performance M-N-C ORR catalysts.

Keywords

Oxygen reduction reaction / M-N-C electrocatalysts / coordination shell

References

[1] Wang XX,Wu G.Achievements, challenges and perspectives on cathode catalysts in proton exchange membrane fuel cells for transportation.Nat Catal2019;2:578-89

[2] Xia Q,Zhao L.Carbon-supported single-atom catalysts for advanced rechargeable metal-air batteries.Energy Mater2022;2:200015

[3] Staffell I,Velazquez Abad A.The role of hydrogen and fuel cells in the global energy system.Energy Environ Sci2019;12:463-91

[4] Yeager E.Electrocatalysts for O₂ reduction.Electrochim Acta1984;29:1527-37

[5] Gong X,Han C,Mei X.Heterogeneous single-atom catalysts for energy process: recent progress, applications and challenges.Energy Mater2023;3:300016

[6] Li Z,Xu B,Zhu W.Electrochemically nitrate remediation by single-atom catalysts: advances, mechanisms, and prospects.Energy Mater2024;4:400046

[7] Zitolo A,Armel V.Identification of catalytic sites for oxygen reduction in iron- and nitrogen-doped graphene materials.Nat Mater2015;14:937-42

[8] Jia Q,Hafiz H.Experimental observation of redox-induced Fe-N switching behavior as a determinant role for oxygen reduction activity.ACS Nano2015;9:12496-505

[9] Wu F,He CT.Single-atom Co-N₄ electrocatalyst enabling four-electron oxygen reduction with enhanced hydrogen peroxide tolerance for selective sensing.J Am Chem Soc2020;142:16861-7

[10] Li Z,Xu C.Engineering the electronic structure of single-atom iron sites with boosted oxygen bifunctional activity for zinc-air batteries.Adv Mater2023;35:e2209644

[11] He Y.PGM-free oxygen-reduction catalyst development for proton-exchange membrane fuel cells: challenges, solutions, and promises.ACC Mater Res2022;3:224-36

[12] Ji S,Hao H.Matching the kinetics of natural enzymes with a single-atom iron nanozyme.Nat Catal2021;4:407-17

[13] Li X,Liu L.Chemical vapor deposition for N/S-doped single Fe site catalysts for the oxygen reduction in direct methanol fuel cells.ACS Catal2021;11:7450-9

[14] Zhou S,Xia J.FeN₃S₁-OH single-atom sites anchored on hollow porous carbon for highly efficient pH-universal oxygen reduction reaction.Small2024;20:e2310224

[15] Peng L,Yang Y.Mesopore-rich Fe-N-C catalyst with FeN₄-O-NC single-atom sites delivers remarkable oxygen reduction reaction performance in alkaline media.Adv Mater2022;34:e2202544

[16] Zhao K,Li Y.Insight into the mechanism of axial ligands regulating the catalytic activity of Fe-N₄ sites for oxygen reduction reaction.Adv Energy Mater2022;12:2103588

[17] Sarma BB,Doronkin DE.Design of single-atom catalysts and tracking their fate using operando and advanced X-ray spectroscopic tools.Chem Rev2023;123:379-444 PMCID:PMC9837826

[18] Chen Y,Zhao S.Enhanced oxygen reduction with single-atomic-site iron catalysts for a zinc-air battery and hydrogen-air fuel cell.Nat Commun2018;9:5422 PMCID:PMC6303331

[19] Yin H,Lu B.Phosphorus-driven electron delocalization on edge-type FeN₄ active sites for oxygen reduction in acid medium.ACS Catal2021;11:12754-62

[20] Wang L,Zhang W,Yuan ZY.Boosting oxygen electrocatalytic performance of Cu atom by engineering the d-band center via secondary heteroatomic phosphorus modulation.Appl Catal B Environ2023;338:123043

[21] Qin J,Zou P,Wang C.Altering ligand fields in single-atom sites through second-shell anion modulation boosts the oxygen reduction reaction.J Am Chem Soc2022;144:2197-207

[22] Liu J,Yuan S,Wang Q.High-coordination Fe-N₄SP single-atom catalysts via the multi-shell synergistic effect for the enhanced oxygen reduction reaction of rechargeable Zn-air battery cathodes.Energy Environ Sci2024;17:249-59

[23] Chen Z,Ding J.Unraveling the origin of sulfur-doped Fe-N-C single-atom catalyst for enhanced oxygen reduction activity: effect of iron spin-state tuning.Angew Chem Int Ed2021;60:25404-10

[24] Zhao Y,Huo J.Epoxy-rich Fe single atom sites boost oxygen reduction electrocatalysis.Angew Chem Int Ed2023;62:e202308349

[25] Shen G,Pan L.Regulating the spin state of Fe^III by atomically anchoring on ultrathin titanium dioxide for efficient oxygen evolution electrocatalysis.Angew Chem Int Ed2020;59:2313-7

[26] Zhang J,Chen C.Tuning the coordination environment in single-atom catalysts to achieve highly efficient oxygen reduction reactions.J Am Chem Soc2019;141:20118-26

[27] Zhou Y,Tao X.Boosting oxygen electrocatalytic activity of Fe-N-C catalysts by phosphorus incorporation.J Am Chem Soc2023;145:3647-55 PMCID:PMC9936543

[28] Chang H,Liu X,Xie Y.Dual MOF-derived Fe/N/P-tridoped carbon nanotube as high-performance oxygen reduction catalysts for zinc-air batteries.Appl Catal B Environ2023;327:122469

[29] Huang ZF,Dou S,Wang J.Strategies to break the scaling relation toward enhanced oxygen electrocatalysis.Matter2019;1:1494-518

[30] Han J,Guo K.The “pull effect” of a hanging ZnII on improving the four-electron oxygen reduction selectivity with Co porphyrin.Angew Chem Int Ed2024;63:e202409793

[31] Wang Z,Liu Y.Dual-atomic-site catalysts for molecular oxygen activation in heterogeneous thermo-/electro-catalysis.Angew Chem Int Ed2023;62:e202301483

[32] Wei S,Wang Z,Bu XH.Planar chlorination engineering: a strategy of completely breaking the geometric symmetry of Fe-N₄ site for boosting oxygen electroreduction.Adv Mater2024;36:e2404692

[33] Yin L,Sun M,Huang B.Heteroatom-driven coordination fields altering single cerium atom sites for efficient oxygen reduction reaction.Adv Mater2023;35:2302485

[34] Li H,Yan G.Ternary heteroatomic doping induced microenvironment engineering of low Fe-N₄-loaded carbon nanofibers for bifunctional oxygen electrocatalysis.Small2024;20:e2304844

[35] Sun Z,Cao L.Understanding synergistic catalysis on Cu-Se dual atom sites via operando X-ray absorption spectroscopy in oxygen reduction reaction.Angew Chem Int Ed2023;62:e202217719

[36] Niu Z,Qiao Z.Long-range regulation of Se doping for oxygen reduction of atomically dispersed Sb catalysts for ultralow-temperature solid-state Zn-air batteries.ACS Catal2023;13:7122-31

[37] Wang Q,Xiao X.Sustainable zinc-air battery chemistry: advances, challenges and prospects.Chem Soc Rev2023;52:6139-90

[38] Liu S,Zhou S.Metal-organic-framework-derived hybrid carbon nanocages as a bifunctional electrocatalyst for oxygen reduction and evolution.Adv Mater2017;29:1700874

[39] Liu M,Cao S.A “pre-constrained metal twins” strategy to prepare efficient dual-metal-atom catalysts for cooperative oxygen electrocatalysis.Adv Mater2022;34:2107421

[40] Chen J,Fan C.Dual single-atomic Ni-N₄ and Fe-N₄ sites constructing janus hollow graphene for selective oxygen electrocatalysis.Adv Mater2020;32:2003134

[41] Guo D,Akiba C,Kondo T.Active sites of nitrogen-doped carbon materials for oxygen reduction reaction clarified using model catalysts.Science2016;351:361-5

[42] Yu W,Qin Y.The synergistic effect of pyrrolic-N and pyridinic-N with Pt under strong metal-support interaction to achieve high-performance alkaline hydrogen evolution.Adv Energy Mater2022;12:2200110

[43] Zitolo A,Mineva T.Identification of catalytic sites in cobalt-nitrogen-carbon materials for the oxygen reduction reaction.Nat Commun2017;8:957 PMCID:PMC5715157

[44] Zhang N,Chen M.High-purity pyrrole-type FeN₄ sites as a superior oxygen reduction electrocatalyst.Energy Environ Sci2020;13:111-8

[45] Yang H,Rao D.Designing superior bifunctional electrocatalyst with high-purity pyrrole-type CoN₄ and adjacent metallic cobalt sites for rechargeable Zn-air batteries.Energy Storage Mater2022;46:553-62

[46] Ha Y,Yan X.Atomically dispersed Co-pyridinic N-C for superior oxygen reduction reaction.Adv Energy Mater2020;10:2002592

[47] Li L,Han G.Tailoring the stability of Fe-N-C via pyridinic nitrogen for acid oxygen reduction reaction.Chem Eng J2022;437:135320

[48] Ni L,Wagner S,Krewald V.Identification of the catalytically dominant iron environment in iron- and nitrogen-doped carbon catalysts for the oxygen reduction reaction.J Am Chem Soc2022;144:16827-40

[49] Hu X,Chen L.What is the real origin of the activity of Fe-N-C electrocatalysts in the O₂ reduction reaction? Critical roles of coordinating pyrrolic N and axially adsorbing species.J Am Chem Soc2022;144:18144-52

[50] Gu Y,Liu J.Enriching H₂O through boron nitride as a support to promote hydrogen evolution from non-filtered seawater.EcoEnergy2023;1:405-13

[51] Liu S,Wu G.Solving the activity-stability trade-off riddle.Nat Catal2021;4:6-7

[52] Cui L,Xie H.Overcoming the activity-stability trade-off in heterogeneous electro-Fenton catalysis: encapsulating carbon cloth-supported iron oxychloride within graphitic layers.ACS Catal2022;12:13334-48

[53] Li J,Zitolo A.Identification of durable and non-durable FeN_x sites in Fe-N-C materials for proton exchange membrane fuel cells.Nat Catal2021;4:10-9

[54] Liu S,Zachman MJ.Atomically dispersed iron sites with a nitrogen-carbon coating as highly active and durable oxygen reduction catalysts for fuel cells.Nat Energy2022;7:652-63

[55] Bai J,Xu M.Monosymmetric Fe-N₄ sites enabling durable proton exchange membrane fuel cell cathode by chemical vapor modification.Nat Commun2024;15:4219 PMCID:PMC11101623

[56] Wang W,Mukerjee S.Recent insights into the oxygen-reduction electrocatalysis of Fe/N/C materials.ACS Catal2019;9:10126-41

[57] Zhang H,Wang M.Single atomic iron catalysts for oxygen reduction in acidic media: particle size control and thermal activation.J Am Chem Soc2017;139:14143-9

[58] Ni B,Zhang G.Second-shell N dopants regulate acidic O₂ reduction pathways on isolated Pt sites.J Am Chem Soc2024;146:11181-92

[59] Liu L.Metal catalysts for heterogeneous catalysis: from single atoms to nanoclusters and nanoparticles.Chem Rev2018;118:4981-5079 PMCID:PMC6061779

[60] Lu J,Guo Y.Cobalt atom-cluster interactions synergistically enhance the activity of oxygen reduction reaction in seawater.Energy Storage Mater2024;65:103093

[61] Wang Z,Ye Q.Construction of Fe nanoclusters/nanoparticles to engineer FeN₄ sites on multichannel porous carbon fibers for boosting oxygen reduction reaction.Adv Funct Mater2024;34:2315150

[62] Liang C,Zhang T.Cu nanoclusters accelerate the rate-determining step of oxygen reduction on Fe-N-C in all pH range.Adv Energy Mater2024;14:2303935

[63] Chen Y,Wang Y.A binary single atom Fe₃C|Fe-N-C catalyst by an atomic fence evaporation strategy for high performance ORR/OER and flexible zinc-air battery.Chem Eng J2023;454:140512

[64] Chang J,Yu J.A Fe single atom seed-mediated strategy toward Fe₃C/Fe-N-C catalysts with outstanding bifunctional ORR/OER activities.Adv Sci2023;10:e2301656 PMCID:PMC10401088

[65] Zhu W,Douglin JC.Multi-scale study on bifunctional Co/Fe-N-C cathode catalyst layers with high active site density for the oxygen reduction reaction.Appl Catal B Environ2021;299:120656

[66] Wu Y,Geng S.PtFe nanoalloys supported on Fe-based cubic framework as efficient oxygen reduction electrocatalysts for proton exchange membrane fuel cells.Adv Funct Mater2024;34:2307297

[67] Wang F,Li J.Which is best for ORR: single atoms, nanoclusters, or coexistence?.ACS Energy Lett2024;9:93-101

[68] Liu M,Yang TC.Synergies of Fe single atoms and clusters on N-doped carbon electrocatalyst for pH-universal oxygen reduction.Small Methods2021;5:e2001165

[69] Han A,Wan X.Construction of Co₄ atomic clusters to enable Fe-N₄ motifs with highly active and durable oxygen reduction performance.Angew Chem Int Ed2023;62:e202303185

[70] Li Y,Shi K.Single-atom Mn catalysts via integration with Mn sub nano-clusters synergistically enhance oxygen reduction reaction.Small2024;20:e2309727

[71] Yuan LJ,Shen LX.d-orbital electron delocalization realized by axial Fe₄C atomic clusters delivers high-performance Fe-N-C catalysts for oxygen reduction reaction.Adv Mater2023;35:e2305945

[72] Jiang WJ,Li L.Understanding the high activity of Fe-N-C electrocatalysts in oxygen reduction: Fe/Fe₃C nanoparticles boost the activity of Fe-N_x.J Am Chem Soc2016;138:3570-8

[73] Chen G,Xue S.Exceptionally bifunctional ORR/OER performance via synergistic atom-cluster interaction.Small2024;20:e2308192

[74] Cui X,Lei S.Simultaneously crafting single-atomic Fe sites and graphitic layer-wrapped Fe₃C nanoparticles encapsulated within mesoporous carbon tubes for oxygen reduction.Adv Funct Mater2021;31:2009197

[75] Wei X,Wu N.Synergistically enhanced single-atomic site Fe by Fe₃C@C for boosted oxygen reduction in neutral electrolyte.Nano Energy2021;84:105840

[76] Lee Y,Jang H.Very strong interaction between FeN₄ and titanium carbide for durable 4-electron oxygen reduction reaction suppressing catalyst deactivation by peroxide.J Mater Chem A2022;10:24041-50

[77] Pan Y,Mi W.Single-atomic Mn sites coupled with Fe₃C nanoparticles encapsulated in carbon matrixes derived from bimetallic Mn/Fe polyphthalocyanine conjugated polymer networks for accelerating electrocatalytic oxygen reduction.Nano Res2022;15:7976-85

[78] Xu C,Liu J.Accelerating the oxygen adsorption kinetics to regulate the oxygen reduction catalysis via Fe₃C nanoparticles coupled with single Fe-N₄ sites.Energy Storage Mater2022;51:149-58

[79] Bae G,Oh HS.Operando stability of single-atom electrocatalysts.Angew Chem Int Ed2023;62:e202219227

[80] Choi CH,Chung MW.The Achilles’ heel of iron-based catalysts during oxygen reduction in an acidic medium.Energy Environ Sci2018;11:3176-82

[81] Bae G,Ji SG,Choi CH.pH effect on the H₂O₂-induced deactivation of Fe-N-C catalysts.ACS Catal2020;10:8485-95

[82] Li Y,Lu BA,Zhang JN.Unravelling the role of hydrogen peroxide in pH-dependent ORR performance of Mn-N-C catalysts.Appl Catal B Environ2024;342:123458

[83] Luo E,Wang X.Single-atom Cr-N₄ sites designed for durable oxygen reduction catalysis in acid media.Angew Chem Int Ed2019;58:12469-75

[84] Guo Y,Xiao Y.Stabilizing Fe single atom catalysts by implanting Cr atomic clusters to boost oxygen reduction reaction.Appl Catal B Environ Energy2024;344:123679

[85] Lawler R,Ham HC.CeO₂ (111) surface with oxygen vacancy for radical scavenging: a density functional theory approach.J Phys Chem C2020;124:20950-9

[86] Karakoti A,Dowding JM,Self WT.Redox-active radical scavenging nanomaterials.Chem Soc Rev2010;39:4422-32

[87] Xie H,Hu G.Ta-TiO_x nanoparticles as radical scavengers to improve the durability of Fe-N-C oxygen reduction catalysts.Nat Energy2022;7:281-9

[88] Li J,Kim YS.Stabilizing single-atom iron electrocatalysts for oxygen reduction via ceria confining and trapping.ACS Catal2020;10:2452-8

[89] Cheng X,Yin S.Instantaneous free radical scavenging by CeO₂ nanoparticles adjacent to the Fe-N₄ active sites for durable fuel cells.Angew Chem Int Ed2023;62:e202306166

[90] Gao XB,Xu W.Mechanism of particle-mediated inhibition of demetalation for single-atom catalytic sites in acidic electrochemical environments.J Am Chem Soc2023;145:15528-37

[91] Bae G,Han MH.Unravelling the complex causality behind Fe-N-C degradation in fuel cells.Nat Catal2023;6:1140-50

[92] Mechler AK,Armel V.Stabilization of iron-based fuel cell catalysts by non-catalytic platinum.J Electrochem Soc2018;165:F1084-91

[93] Xiao F,Xu GL.Atomically dispersed Pt and Fe sites and Pt-Fe nanoparticles for durable proton exchange membrane fuel cells.Nat Catal2022;5:503-12

[94] Zhou H,Kou Z.Negative pressure pyrolysis induced highly accessible single sites dispersed on 3D graphene frameworks for enhanced oxygen reduction.Angew Chem Int Ed2020;59:20465-9

[95] Yu Y,Liu Z.Activation of Ga liquid catalyst with continuously exposed active sites for electrocatalytic C-N coupling.Angew Chem Int Ed2024;63:e202402236

[96] Yuan S,Zhang Y.Tuning the catalytic activity of Fe-phthalocyanine-based catalysts for the oxygen reduction reaction by ligand functionalization.ACS Catal2022;12:7278-87

[97] Fei H,Chen D.Single atom electrocatalysts supported on graphene or graphene-like carbons.Chem Soc Rev2019;48:5207-41

[98] Zhao Z,Yu S.Single-atom Zn with nitrogen defects on biomimetic 3D carbon nanotubes for bifunctional oxygen electrocatalysis.J Colloid Interface Sci2023;650:934-42

[99] Li L,Wang J.Atomically dispersed Co in a cross-channel hierarchical carbon-based electrocatalyst for high-performance oxygen reduction in Zn-air batteries.J Mater Chem A2022;10:18723-9

[100] Tian H,Zhang P.High durability of Fe-N-C single atom catalysts with carbon vacancies towards oxygen reduction reaction in alkaline media.Adv Mater2023;35:2210714

[101] Liu K,Lin Y.Insights into the activity of single-atom Fe-N-C catalysts for oxygen reduction reaction.Nat Commun2022;13:2075 PMCID:PMC9018836

[102] Wang X,Mao X.Edge-rich Fe-N₄ active sites in defective carbon for oxygen reduction catalysis.Adv Mater2020;32:e2000966

[103] Fu X,Ren B.Tailoring FeN₄ sites with edge enrichment for boosted oxygen reduction performance in proton exchange membrane fuel cell.Adv Energy Mater2019;9:1803737

[104] Kong F,Chen M.Creation of densely exposed and cavity-edged single Fe active sites for enhanced oxygen electroreduction.Appl Catal B Environ2022;317:121768

[105] Zhang R,Tao Y.Edge-site engineering of defective Fe-N₄ nanozymes with boosted catalase-like performance for retinal vasculopathies.Adv Mater2022;34:e2205324

[106] Cui L,Liu G,Li B.Rich edge-hosted single-atomic Cu-N₄ sites for highly efficient oxygen reduction reaction performance.J Colloid Interface Sci2022;622:209-17

[107] Mun Y,Kim K.Versatile strategy for tuning ORR activity of a single Fe-N₄ site by controlling electron-withdrawing/donating properties of a carbon plane.J Am Chem Soc2019;141:6254-62

[108] Gu Y,Zhang H,Xiong SL.Activation of main-group antimony atomic sites for oxygen reduction catalysis.Angew Chem Int Ed2022;61:e202202200

[109] Chang X,Wang D,Guo Y.Flash dual-engineering of surface carboxyl defects and single Cu atoms of g-C₃N₄ via unique CO₂ plasma immersion approach for boosted photocatalytic activity.Mater Today Adv2022;15:100274

[110] Lv M,Huang N.Precisely engineering asymmetric atomic CoN₄ by electron donating and extracting for oxygen reduction reaction.Angew Chem Int Ed2024;63:e202315802

[111] Wei X,Xu H.Synergistic effect of organic ligands on metal site spin states in 2D metal-organic frameworks for enhanced ORR performance.ACS Catal2023;13:15663-72

[112] Liu M,Peng T.Fe-NC single-atom catalyst with hierarchical porous structure and P-O bond coordination for oxygen reduction.ACS Energy Lett2023;8:4531-9

[113] Tang C,Li H.Tailoring acidic oxygen reduction selectivity on single-atom catalysts via modification of first and second coordination spheres.J Am Chem Soc2021;143:7819-27

[114] Qiao Y,Hu Y.Sulfuration of an Fe-N-C catalyst containing Fe_xC/Fe species to enhance the catalysis of oxygen reduction in acidic media and for use in flexible Zn-air batteries.Adv Mater2018;30:e1804504

[115] Chi B,Yang X.Promoting ZIF-8-derived Fe-N-C oxygen reduction catalysts via Zr doping in proton exchange membrane fuel cells: durability and activity enhancements.ACS Catal2023;13:4221-30

[116] Zhu P,Wang X.Regulating the FeN₄ moiety by constructing Fe-Mo dual-metal atom sites for efficient electrochemical oxygen reduction.Nano Lett2022;22:9507-15

[117] Zhang M,Chen J.High-loading Co single atoms and clusters active sites toward enhanced electrocatalysis of oxygen reduction reaction for high-performance Zn-air battery.Adv Funct Mater2023;33:2209726

[118] Liu H,Khan J.Decorating single-atomic Mn sites with FeMn clusters to boost oxygen reduction reaction.Angew Chem Int Ed2023;62:e202214988

[119] Wei X,Cai W.Pt nanoparticle-Mn single-atom pairs for enhanced oxygen reduction.ACS Nano2024;18:4308-19

[120] Xu X,Lu W.Collective effect in a multicomponent ensemble combining single atoms and nanoparticles for efficient and durable oxygen reduction.Angew Chem Int Ed Engl2024;63:e202400765

[121] Zhang Y,Liu X.Vacancy-enhanced Sb-N₄ sites for the oxygen reduction reaction and Zn-air battery.Nano Lett2024;24:4291-9

[122] Lyu L,Lee S.Oxygen reduction kinetics of Fe-N-C single atom catalysts boosted by pyridinic N vacancy for temperature-adaptive Zn-air batteries.J Am Chem Soc2024;146:4803-13

[123] Liu H,Sun Y.Revisiting the role of sulfur functionality in regulating the electron distribution of single-atomic Fe sites toward enhanced oxygen reduction.Adv Funct Mater2023;33:2304074

[124] Qu Y,Chen W.Direct transformation of bulk copper into copper single sites via emitting and trapping of atoms.Nat Catal2018;1:781-6

[125] Liu H,Arbiol J,Tang P.Catalytic reactivity descriptors of metal-nitrogen-doped carbon catalysts for electrocatalysis.EcoEnergy2023;1:154-85