Confined Ir single sites with triggered lattice oxygen redox: Toward boosted and sustained water oxidation catalysis

•First demonstration of lattice oxygen redox in Ir single-site catalyst (Ir–MnO2)•Ir–MnO2 exhibited an over 42 times mass activity than that commercial IrO2•Ir–MnO2 show only 15 mV increasement overpotential after 650 h durability test Proton exchange membrane water electrolyzers (PEMWEs) represent a promising technology to efficiently convert renewable energy into high-quality hydrogen. However, their scale-up is restricted by the high cost state-of-the-art Ir-based catalysts anodic evolution reaction (OER). Developing highly active and stable OER electrocatalysts with low content thus imperative. In this work, novel single site embedded ?-MnO2 (with 0.87 atom % Ir) fabricated through simple thermal decomposition procedure. Benefiting from locally activated redox, as-prepared sample outstanding electrocatalytic long-term stability, much superior IrO2. This work demonstrates new strategy precisely modulate physicochemical properties confined sites boost stability simultaneously system. Efficient for (OER) acid are critical development clean conversion schemes. Lattice-oxygen-mediated mechanism (LOM) has been developed kinetic via triggering redox. promoted intrinsic compromised due bulk structure reconstruction during OER. Here, we demonstrate Ir-doping can effectively address challenge. Attributing carefully defined chelation environment Ir, increased Ir–O covalency engaged oxidation have observed. More importantly, triggered LOM introduces no As result, constructed (Ir–MnO2) more IrO2 as well increase overpotential. Our opens up feasible simultaneously. The imperative usage iridium toward plagued proton electrolysis (PEMWE) decades.1Lagadec M.F. Grimaud A. Water electrolysers closed open electrochemical systems.Nat. Mater. 2020; 19: 1140-1150Crossref PubMed Scopus (104) Google Scholar, 2Carmo M. Fritz D.L. Mergel J. Stolten D. A comprehensive review on PEM electrolysis.Int. Hydr. Energy. 2013; 38: 4901-4934Crossref (2461) 3Song H.J. Yoon H. Ju B. Kim D.W. Highly efficient perovskite-based acidic environments: mini review.Adv. Energy https://doi.org/10.1002/aenm.202002428Crossref (33) Scholar current guiding principles lowering loadings mainly based either increasing utilization Ir4Chen Cui P. Zhao G. Rui K. Lao Chen Y. Zheng X. Jiang Pan Dou S.X. Sun W. Low-coordinated oxide graphitic carbon nitride evolution.Angew. Chem. Int. Ed. 2019; 36: 12540-12544Crossref (117) Scholar,5Oakton E. Lebedev Povia Abbott D.F. Fabbri Fedorov Nachtegaal Copéret C. Schmidt T.J. IrO2-TiO2: high-surface-area, active, electrocatalyst reaction.ACS Catal. 2017; 7: 2346-2352Crossref (176) or boosting its activity, i.e., turn frequency (TOF) per using following two strategies: (1) Regulating adsorption energies intermediates (O?, OOH?, OH?) according Sabatier principle, adsorbate (AEM).6Man I.C. Su H.-Y. Calle-Vallejo F. Hansen H.A. Martínez J.I. Inoglu N.G. Kitchin Jaramillo T.F. Nørskov J.K. Rossmeisl Universality electrocatalysis surfaces.ChemCatChem. 2011; 3: 1159-1165Crossref (2362) 7Fabbri Habereder Waltar Kötz R. Developments perspectives oxide-based reaction.Catal. Sci. Technol. 2014; 4: 3800-3821Crossref 8Shi Q. Zhu Du Lin Robust noble metal-based reaction.Chem. Soc. Rev. 48: 3181-3192Crossref AEM limited so called scaling relationship between OH? resulting minimum theoretical 0.37 V. (2) Pushing go beyond top volcano introducing variables (i.e., introduction second sites,9Fei Dong Feng Allen C.S. Wan Volosskiy Li Z. Wang et al.General synthesis definitive structural identification MN4C4 single-atom tunable activities.Nat. 2018; 1: 63-72Crossref (956) hydrogen bond,10Doyle A.D. Montoya J.H. Vojvodic Improving electrochemistry nanoscopic confinement.ChemCatChem. 2015; 5: 738-742Crossref (81) acceptors11Halck N.B. Petrykin Krtil Beyond limitations – reaction.Phys. Phys. 16: 13682-13688Crossref (225) Scholar) devising follow lattice-oxygen-mediated (LOM).12Song Wei Huang Z.F. Liu Zeng L. Xu Z.J. fundamentals designing electrocatalysts.Chem. 49: 2196-2214Crossref Scholar,13Reier T. Nong H.N. Teschner Schlögl Strasser Electrocatalytic environments - mechanisms catalysts.Adv. 1601275Crossref (553) bypass generation immediate avoiding relation OOH?.14Yoo J.S. Rong Kolpak A.M. Role participation understanding trends perovskites.ACS 8: 4628-4636Crossref (165) mechanism, participates process own oxidation. Therefore, trigger LOM, O 2p band needs be upshifted closely approximate Fermi level (EF), thereby orbital overlap metal d (M–O bond covalency15Yagi S. Yamada I. Tsukasaki Seno Murakami Fujii Umezawa N. Abe Nishiyama Mori Covalency-reinforced catalyst.Nat. Commun. 6: 8249Crossref (294) making energetically favorable.16Fabbri Oxygen reaction—the enigma electrolysis.ACS 9765-9774Crossref Scholar,17Hwang Rao R.R. Giordano Katayama Yu Shao-Horn Perovskites catalysis electrocatalysis.Science. 358: 751-756Crossref (678) such, promotion achieved strengthening covalency.18Hao Tan He Lei Zhang Dopants fixation ruthenium activity.Nat. 11: 5368Crossref (66) Scholar,19Kim Shih P.C. Qin Al-Bardan C.J. Yang porous pyrochlore Y2 [Ru1.6 Y0.4 ]O7-delta enhanced performance towards media.Angew. Engl. 57: 13877-13881Crossref (70) To meet such goal, modulations IrMOx (M = metal) compounds currently carried out,20Nong Reier Oh H.-S. Gliech Paciok Vu T.H.T. Heggen Petkov al.A unique ligand facilitates hole-doped IrNiOx core–shell electrocatalysts.Nat. 841-851Crossref (242) 21Grimaud Diaz-Morales O. Han Hong W.T. Lee Y.L. Stoerzinger K.A. Koper M.T.M. Activating reactions oxides catalyse evolution.Nat. 9: 457-465Crossref (867) 22Grimaud Demortière Saubanère Dachraoui Duchamp Doublet M.-L. Tarascon J.-M. Activation surface iridium-based model reaction.Nat. 2: 17002Crossref perovskite, double pyrochlore, etc., widely studied. By substituting M cations at lower valence states, becomes positively charged (due charge conservation principle) states lowered states. higher generally switching LOM.23Huang Z.-F. Song Strategies break electrocatalysis.Matter. 1494-1518Abstract Full Text PDF (149) Similar results obtained Co–Zn oxyhydroxide reported al.24Huang Xi Nsanzimana J.M.V. Chemical origin 329-338Crossref (528) alkaline electrolyte. boosted often counterbalanced destabilization,25Rong Parolin fundamental evolution.ACS 2016; 1153-1158Crossref (250) ascribable cationic dissolution (in IrMOx) condition.22Grimaud Even worse, dynamic formation large number vacancies (OV) drives migration replenish OV, phase insufficient durability.22Grimaud Scholar,26Pan Zhong Ge Veder J.M. Guan O'Hayre al.Direct evidence perovskite participation.Nat. 2002Crossref (162) considered uncompetitive those terms feasibility real world application, spite catalytic efficiencies.27Yao Hu Z.-Q. Yao Zang Wu al.Engineering electronic Ru compressive strain boosts electrocatalysis.Nat. 304-313Crossref (408) Scholar,28Cao Luo Shen al.Dynamic single-atomic 10: 4849Crossref (186) We reasoned problem not invincible, provided aspects considered: Discovering pertinent while rivaling cation dissolution, selecting site.29Wang Y.-R. Chorkendorff Acid-stable electrocatalysis.ACS Lett. 2905-2908Crossref (31) Stabilizing against accelerated excessive OV LOM,26Pan Scholar,30Zhu Choi al.Tuning proton-coupled electron transfer crystal orientation oxidization oxides.Nat. 4299Crossref (38) regulating coordination bulky oxygen. Combining these factors, compound, isolatedly regulated atoms kept inert resistive fast diffusion, will effective problem. other words, dispersing MOx substrate, which possesses favorable parameters (trigger LOM), diffusion rate ensure might able ultimately solve primary bottleneck LOM. Through regulation, concurrently issue catalysts. Stimulated above envision, herein achieved, first time, activation (denoted Ir–MnO2). Compared oxides, atomic isolated dispersed ?-MnO231Li Ooka Bonnet Hayashi Nakamura Stable potential windows Electrocatalysisby manganese Under conditions.Angew. 58: 5054-5058Crossref (98) accommodates latter exhibits shortened length (?5% shrinkage compared IrO2). Using situ 18O isotope labeling differential spectrometry (DEMS), provide direct experimental turned sites. Ir–MnO2 presented (218 @10 mA cm?2 0.5 H2SO4) quite impressive TOF (7.7 s?1) 300 mV. Moreover, localized activation, anionic evidenced retained test. conclude, offer without compromising optimized. choose (Figure S1) supporting matrix excellent under condition.31Li prepare series doped samples different doping levels, Mn(NO3)2 mixture H2IrCl6 was out (Note S1). Within synthetic method, 5.13 wt affecting S2). Due compositional similarity MnO2, hereafter denoted Ir–MnO2, selected detailed elaboration. physical before were characterized systemically (Figures 1A S2–S8). High-resolution transmission microscope (HRTEM) images 1B 1C) confirm crystalline doping, inter-growth pyrolusite ramsdellite phases unambiguously identified S1).32Schilling Dahn J.R. Fits [gamma]-MnO2 disordered dioxides.J. Appl. Crystallogr. 1998; 396-406Crossref (17) While particles observed HRTEM S3), inductively coupled plasma-optical emission (ICP-OES; Table S1), dispersive spectroscopy (EDS; Figure S5), elemental mapping 1D), X-ray photoelectron (XPS; S6) all suggest presence sample, corroborating ?-MnO2. ICP-OES (Table sensitive XPS characterization reveal similar homogeneously, rather sitting surface. Aberration corrected high-angle annular dark-field scanning (HAADF-STEM; Figures 1E 1F) result clearly verifies isolation S7). atoms, notable scattered bright dots lattice, located exactly same columns Mn 1F, 1G, S9), suggesting replace ?-MnO2.33Wang Z.L. Xiang Gu Ultrahigh-loading NiO dramatically enhance reaction.J. Am. 142: 7425-7433Crossref (183) X?ray diffraction (XRD) patterns S8A) prepared typical peaks ?-MnO2.31Li 2? values shifted slightly smaller angles expansion induced ionic radii difference (0.625 Å) (0.530 Å)34Shannon R.D. Revised Effective ionic-radii systematic studies interatomic distances halides chalogenids.Acta Cryst. 1976; 32: 751-767Crossref (52148) S8B), also indicates should substitute larger (1.36 Å).35Bisht Shivakumara Sharma Pt-doped Pt-supported La1–xSrxCoO3: comparative Pt4+and Pt0 CO poisoning effect formic methanol electro-oxidation.J. 25: 14126-14134Crossref Rietveld refinement, XRD data satisfactorily refined S10). Specifically, resembles refinements S2; S11), it occupy position Ir–MnO2.36Nikam Rayaprol Mukherjee Kaushik S.D. Goyal P.S. Babu P.D. Radha Siruguri Structure magnetic ?-Fe2O3.Phys. 574: 411663Crossref (8) further employed absorption fine (XAFS) study chemical state atomically Ir. First, 4f spectrum 2A) 0.35 eV positive shift binding (65.50 4f5/2) regard (65.15 4f5/2), Ir.37Chen Sherburne Ager 3rd, J.W. Fisher A.C. Exceptionally evolved pseudo-cubic acid.Nat. 572Crossref (137) Scholar,38Zheng Shang Cao Si Zhou Intercalated diselenide pH-universal splitting.Angew. 14764-14769Crossref (65) supported near?edge (XANES) spectra. L3-edge white line intensity, representing transition occupied empty 5d demonstrating S12)20Nong comparison IrO2, derivative XANES 2B, insert). average extrapolated calculated +4.75 S13),20Nong Scholar,39Choy J.-H. D.-K. Hwang S.-H. Demazeau Jung D.-Y. EXAFS Ir-O perovskites.J. 1995; 117: 8557-8566Crossref (110) confinement local Mn–O–Ir–O–Mn S14 Note S3, details DFT calculation section). influence bonding feature revealed analyzing extended (EXAFS) 2C, S15, S16). Phase uncorrected Fourier transform (FT-EXAFS) approximately 5% (1.57 (1.65 Å), contraction O.39Choy Scholar,40Görlin Chernev Ferreira de Araújo Dresp Paul Krähnert Dau dynamics, faradaic efficiency, Ni–Fe splitting electrocatalysts.J. 138: 5603-5614Crossref (654) originates distinction shell structures Ir–Mn Ir–Ir scattering paths (represents Ir–O–Mn Ir–O–Ir structure) 2.607 2.914 Å (without correction 2C respectively. provides completely sites, accommodation former leads strength inclined LOM.41Shi Xing Fundamental reaction: catalysts.Nanoscale. 12: 13249-13275Crossref wavelet transforms (WTs) analysis S16), k-space information pertaining sphere lack intensity maximum 8.5 Å?1 corroborates absence Ir–MnO2. It worth noting EXANS spectra almost identical lowest highest S17). On contrary significantly modulated spectra, 2s K-edge XAFS 2E, 2F, S18, S19) obvious primarily (0.87 %). Besides, electric conductivity determined 5.38 5.41 S cm?1 respectively S20A), attributable overall consistent total density (DOS) S20B). safe conclude significant site, hardly influenced doping. control studied H2SO4 (see detail supplemental information). any test, pretreated 10 2 remove possible impurity S4). Second, represents far 3A). Excitingly, reach 218 132 253 ?-MnO2, 3A, inserted). (based gas chromatography, S21) even promising, reaching 766 gIr?1 7.7 s?1, respectively, 1.53 V (versus RHE). corresponds 42.56 (18 gIr?1) 350 (0.022 enhancement Furthermore, outperforms best previously literature, both specific 3B; S4).4Chen Scholar,20Nong Scholar,42Chen Shi Liang Asefa Zou Optimization phase, composition, morphology low-iridium catalysts.Angew. 59: 19654-19658Crossref (41) 43Yin Jin Lu Peng Yan C.H. Iridium coupling media.J. 18378-18386Crossref (105) 44Shang Electron correlations engineer iridates oxidation.Adv. 31e1805104Crossref 45Wu Qu general approach amorphous nanosheets.Nat. 4855Crossref (139) 46Yang Ai Duan al.Efficient face-sharing IrO6 octahedral dimers.Nat. 5236Crossref (185) 47Lim Park Jeon S.S. Roh C.-W. Ultrathin nanoneedles Funct. 28: 1704796Crossref (146) implies attributed dispersion but optimization possibly discussed later. Third, Tafel plots slope 59.61 dec?1 3C), (78.62 dec?1) less (167.39 dec?1). clear t