Metal free and Nonprecious Metal Materials for Energy relevant Electrocatalytic Processes Shizhang Qiao ( 乔世璋 ) s.qiao@adelaide.edu.au The University of Adelaide, Australia 18 19 January 216, Perth 1. ORR Catalysis 2. OER Catalysis OUTLINES 3. HER Catalysis 4. Summary 1
1. ORR and Catalysts Cathodic oxygen reduction reaction (ORR) pathway (2e vs. 4e) Pathway Acidic medium Alkaline medium 4e O 2 +4H + +4e 2H 2 O O 2 +2H 2 O+4e 4OH 2e O 2 +2H + +2e H 2 O 2 O 2 + H 2 O+2e HO 2 +OH H 2 O 2 +2H + +2e 2H 2 O H 2 O+ HO 2 +2e 3OH Pt/C electrode: an efficient cathodic oxygen reduction reaction (ORR) catalyst Low durability (CO poison and Carbon degradation) High Cost, limited supply The main trend in ORR electrode development is replacing precious Pt with higher-performance, lower-cost, and longer-life catalysts! Carbon-based Metal-free ORR Catalysts: Unique electronic properties Zheng, Qiao* et al, Small, 212, 8, 355-3566. (22 citations) 2
Carbon-based -Metal-free Catalysts: g-c3n4 Highest nitrogen content (61%) Highly regular structure Low cost, facile synthesis Potential ORR catalyst, substitute of Pt Non-conductive nature Blocking electron transfers Zheng, Qiao*, et al, Energy Environ. Sci., 212, 5, 6717-6732. (327 citations) Graphene based metal free ORR electrocatalysts Engineering graphene for an enhanced catalytic activity - heteroatoms doping Graphene: semimetal, little catalytic activity Single-doped graphene with heteroatoms: Tailoring the electron-donor property of graphene to enhance its reactivity Dual-or Tri-doped graphene: A synergistic coupling effect to result in a unique electronic structure and further enhanced activity Our strategy (synergistic effects): B,N-graphene S,N-graphene J. Liang, S. Qiao*, et al, Angew. Chem. Int. Ed., 212, 51, 11496. (439 citations) Y. Zheng, S. Qiao*, et al, Angew. Chem. Int. Ed., 213, 52, 311. (258 citations) 3
1.1 B,N-co-doped graphene: synthesis and chemical composition A novel two-step doping process from GO: first N in low temperature then B in high temperature A high purity of B,N co-doped graphene without hybrid h-bn formation Potential synergistic effect: Enhanced ORR electrocatalytic activity. A platform for theoretical calculation: Chemical interaction between B and N. Y. Zheng, Y. Jiao, L. Ge, M. Jaroniec, S.Z. Qiao*, Angew Chem. Int Ed. 213, 52, 311-3116. (258 citations) 1.1 B,N-co-doped graphene: electrocatalytic ORR performances Significantly enhanced ORR performance than single-doped graphene (N-graphene, B- graphene) and one-step synthesized h-bn/graphene hybrid : Closer on-set potential to Pt/C Higher ORR current density Better electrocatalytic efficiency than single-doped graphene and h-bn graphene Higher stability than Pt/C Synergistic effects 1+1>2 Y. Zheng, Y. Jiao, L. Ge, M. Jaroniec, S.Z. Qiao*, Angew Chem. Int Ed. 213, 52, 311-3116. (258 citations) 4
I 25/1/216 1.2 Mesoporous S,raphene Electrocatalyst O 4.6 % C 88.88 % S 2.2 % N 4.5 % C C-S-C 2p 3/2 C-S-C 2p 1/2 O N S 3 6 9 12 15 168 166 164 162 Binding Energy Binding Energy / ev S and N are simultaneously doped into different sites of graphene. Precursors undergo total thermal decomposition, no residual or side products formed. No by-product formation A simple one-pot doping using all solid and commercial precursors J. Liang, S. Qiao*, et al. Angew. Chem. Int. Ed. 212, 51, 11496-115. (438 citations) 1.2 S,N-graphene: ORR activity 2 J / ma cm -2-2 O -4 2 -.9 -.6 -.3..3 E vs. Ag/AgCl / V N 2 J -1 / ma cm -2 4 8 Pt N-S-G S-G G 12.2. -.2 -.4 -.6 -.8 E vs. Ag/AgCl / V J / ma cm -2 4 8 12 rpm 2 rpm.2. -.2 -.4 -.6 -.8 E vs. Ag/AgCl / V J -1 / ma -1 cm 2.4.3.2.1 G S-G N-S-G Pt/C J k / ma cm -2 35 3 25 2 15 1 5 n=4 n=3.6 n=3.3 n=3. n=3..2.3.4.5-1/2 / rpm -1/2 Pt/C N-S-G S-G ORR performance: Much better than S-graphene N-graphene Synergistic effect The interaction of S and N dopants enhance both charge and spin density of active C atom J. Liang, S. Qiao*, et al. Angew. Chem. Int. Ed.. 212, 51, 11496-115. (439 citations) G 5
1.3 Resol+F127 in EtOH PS/Resol/F127 PS Monolith EISA Thermal Polymerize 15 nm 5 nm PS/PF 3D Macropore 2D Mesopore N G N G N OMMC N G N G Melamine g C 3 N 4 Acetone Cyclohexane OMM PF 5 nm 5 nm Dual template to form ordered macropores N Graphene on Carbon N Graphene and mesopores In situ growth of N doped graphene J. Liang, S. Qiao*, et al. Advanced Materials 213, 25, 6226-6231. 1.3 N graphene/hierarchical porous carbon hybrid for ORR dv/d(logd) 1..5 8 Quantity Adsorbed P/P 2..5 1. Advanced Materials. 1 2 3 4 Pore Size / nm J / ma cm -2 E vs. Ag/AgCl / V 2-2 N 2 O 2 J p =1.81 ma cm -2-4 -.9 -.6 -.3..3 E vs. Ag/AgCl / V -.1 -.2 -.3 -.4 -.5 N-OMMC-G N-OMMC MIX -5-4 -3-2 log (i L i)/(i L -i) J / ma cm -2 Tafel Slope / mv dec -1-4 -8 35 28 21 14 7 MIX Pt/C N-OMMC-G N-OMMC. -.4 -.8 E vs. Ag/AgCl / V N-OMMC-G Low Potential High Potential N-OMMC MIX Few layered graphene sheets Large surface area & excellent accessibility Synergistically enhanced ORR performance J. Liang, S. Qiao*, et al. Advanced Materials 213, 25, 6226-6231 (insider Front Cover, 79 citations). 6
1.4 Origin of ORR activity of doped graphene electrocatalysts B, N, O, P, S doped graphenes Molecular orbital concept Y. Jiao, Y. Zheng, M. Jaroniec, S. Qiao*, J. Am. Chem. Soc. 214, 136, 4394-443. (1 citations) a C1s sp 2 C-C b B1s c N1s Pyridinic N Intensity (a.u.) Intensity (a.u.) B 2 O 3 B-2C(-O) BC 3 Intensity (a.u.) Graphitic N Pyrrolic N - 296 292 288 284 28 Binding Energy (ev) 196 192 188 Binding Energy (ev) 44 4 396 Binding Energy (ev) d Intensity (a.u.) O1s O=C C-OH C-O O-C=O epoxy/ pyran e Intensity (a.u.) P2p P-3C(-O) Ph 3 P f Intensity (a.u.) S2p p 1/2 p 3/2 C-S-C 536 532 528 Binding Energy (ev) 14 135 13 125 Binding Energy (ev) 168 166 164 162 16 Binding Energy (ev) Graphite, B, N, O, P, S doped graphenes. Five heteroatoms induce 13 different doping configurations in graphene clusters with very different electronic properties, yielding 32 possible ORR active sites. 7
Exchange current density On set potential 1-5 Pt X-G.2 log(j ) (A/cm 2 ) 1-7 1-9 1-11 B-G O-G P-G G S-G Onset Potential vs. NHE (V). -.2 -.4 predictive value experimental value Free energy (ev) 1-13.8 1. 1.2 1.4 1.6 1.8 2. 2.2 2.4 2.6.3.2.1. -.1 -.2 -.3 U NHE = -.8 V O 2 G OOH* (ev) Pathway selectivity OOH*.16 ev Reaction coordinates g X-G OOH - J k @vs NHE (ma/cm 2 ) -4-3 -2-1 X-G B-G P-G O-G S-G Kinetic current density N B P O S G -6 @ -.1 V (-2.68 ma/cm 2 ) @ -.2 V (-5.23 ma/cm 2 ) -5 @ -.3 V (-6.1 ma/cm 2 ).2.4.6.8 1. G OH* (ev) Y. Jiao, Y. Zheng, M. Jaroniec, S. Qiao*, J. Am. Chem. Soc. 214, 136, 4396-443. (1 citations) G 1.5 Non-noble metal @ N-carbon catalysts: ORR activity spheres square/cubic ellipse (1) Mn N graphene (2) Fe N doped graphitic carbon (3) Ag@N rgo (4) CuO@N rgo Fe N synergistic effect enhanced the ORR performance and change the mechanism; XPS and Raman spectrum proved the existence of Ag N interaction; The ORR performance is close to Pt; The ORR performance is correlated to shape of Mn3O4 nanocrystals. Mn-N Fe-N Ag-N Cu-N (1) Advanced Functional Materials 214, 24, 272; (2) Chemical Communication 213, 49, 775. (3) Chemical Communications 215, 51, 7516; (4) Chemistry of Materials 214, 26, 5868; (5) Journal of Materials Chemistry A 213, 1, 3179. 8
2. OER and Catalysts Challenges in OER process 4OH - 2H 2 O + O 2 + 4e - (in alkaline solutions) 2H 2 O 4H + + O 2 + 4e - (in acidic or neutral solutions) High overpotential Low activity Inferior kinetics OER in alkaline media 2.1 N, O-dual doped carbon-based electrode (substrate-free) O 2 Chen S., Qiao S.Z.* et al. Adv. Mater, 214, 26, 2925-293. (49 citations) 9
2.1 N, O-dual-doped carbon-based Onset potential Current density Tafel slope Catalytic kinetics Durability Stability O 2 Chen S., Qiao S.Z.* et al. Adv. Mater, 214, 26, 2925-293. (49 citations) 2.2 Hydrated oxygen evolution electrocatalyst Hybrid hydrogel Ni Co double hydroxides Dehydrated electrocatalyst Hydrated electrocatalyst Chen S., Duan J., Jaroniec M., Qiao S.Z.*, Angew. Chem. Int. Ed., 213, 52, 13567-1357. (72 citations) 1
2.2 Hydrated oxygen evolution electrocatalyst EIS: internal resistance, favorable transport 12 h chronoamperometric test O 2 Chen S., Duan J., Jaroniec M., Qiao S.Z.*, Angew. Chem. Int. Ed., 213, 52, 13567-1357. (72 citations) 2.3 3D g-c 3 N 4 nanosheet-cnt composite oxygen evolution catalysts exfoliation N 1s C=N-C C 1s C=C Intensity (a.u.) positive CN cycle N(-C) 3 interact with CNT 45 42 399 396 393 Strong interation between CNT and N in g-c3n4 sp 2 C in g-c 3 N 4 -COOH Hight N content of 23.7 wt% O C-OH 292 288 284 28 C N 12 1 8 6 4 2 Binding energy (ev) Ma, T. Y., Qiao, S.Z.*, et al. Angew. Chem. Int. Ed., 214, 53, 7281-7285. (8 citations) 11
2.3 3D g-c 3 N 4 nanosheet-cnt composite oxygen evolution catalysts (a) J (ma cm -2 ) (GSA) 4 2 (d) (a) I ring at E ring = 1.5 V ( A) g-c 3 N 4 NS-CNT IrO 2 -CNT bulk g-c 3 N 4 -CNT CNT g-c 3 N 4 NS 1. 1.2 1.4 1.6 1.8 E vs. RHE (V) 5 4 3 2 1 Catalytic activity Reaction kinetics Long-term stability 4OH - O 2 + 2H 2 O + 4e - O 2 -saturated Low ring current no hydrogen peroxide fourelectron water oxidation 1. 1.2 1.4 1.6 1.8 E vs. RHE (V) Reaction pathway (b) Overpotential vs. RHE (V) (e) (b) I ring at E ring =.4 V ( A).5.4.3 bulk g-c 3 N 4 -CNT 15 mv decade -1 83 mv decade -1 IrO 2 -CNT 9 mv decade -1 g-c 3 N 4 NS-CNT..5 1. 1.5 Log[J (ma cm -2 )] -1-2 -3-4 I disk = N 2 -saturated Pt E ring GC Catalyst OER Pt ORR OH - O 2 OH - I disk = 2 A -5 1 2 3 4 1 2 3 4 5 Time (s) Reaction mechanism (c) J/J (%) (f) (c) J (ma cm -2 ) (GSA) 1 75 5 25 2 4 6 8 1.52 Time (s) 2 4 6 8 1 Time (h) 15 1 5 g-c 3 N 4 NS-CNT IrO 2 -CNT 1 2 3 4 5 Scan rate (mv s -1 ) g-c 3 N 4 NS-CNT g-c 3 N 4 NS-CNT bulk g-c 3 N 4 -CNT 5 mv s -1 5 mv s -1 5 mv s -1 5 mv s -1 1. 1.2 1.4 1.6 1.8 E vs. RHE (V) 2 15 1 5 (J-J )/J (%) 1.58 1.56 1.54 E vs. RHE (V) Mass transportation 86.7% Ma, T. Y., Qiao, S.Z.*, et al. Angew. Chem. Int. Ed., 214, 53, 7281-7285. (8 citations) 2.4 Metal-Organic Framework-Derived Co 3 O 4 -Carbon Porous Nanowire Arrays for Reversible OER/ORR Hydrocarbon layer Cobalt oxygen layer pore size: 5 nm Amorphous Carbon 251 m 2 g 1 Enhanced electron conductivity y C: C: 52.1 52.1 % The highest for nanowire arrays Ma, T. Y., Qiao, S.Z., et al. J. Am. Chem. Soc. 214, 136, 13925-13931. (73 citations) 12
Nanowire arrays on Cu foil o High conductivity by in situ carbon introduction Well aligned nanowire array o Large active surface area o o Favourable reaction kinetics in the nanowire array structure Strong binding between nanowire arrays and Cu substrate Slit like mesopores (311) plane of Co 3 O 4 Closely interacted C and Co 3 O 4 Homogeneously distributed Co and C High OER activity Ma, T. Y., Qiao, S.Z., et al. J. Am. Chem. Soc. 214, 136, 13925-13931. (73 citations) High OER activity Favourable kinetics High efficient reaction pathway High OER activity Favorable kinetics 4 e pathway Faradaic effciency : 99.3% High Faradaic efficiency Long term durability Strong cyclic stability Strong methanol tolerance Methanol addition Bi function for both ORR and OER. Excellent reversibility: E =.74 V Ma, T. Y., Qiao, S.Z., et al. J. Am. Chem. Soc. 214, 136, 13925-13931. (73 citations) 13
3. HER and Catalysts 3.1 metal free g-c3n4@graphene First record of electrocatalytic hydrogen evolution reaction (HER) by a non metallic material. Comparable electrocatalytic activity with state of the art metallic catalysts. A combined theoretical and experimental study. Aberration corrected HRTEM and HR EELS mapping The hybrid (g C 3 N 4 @Ngraphene) is a ultrathin nanosheet with some g C 3 N 4 nanodomain (islands) on the surface. Y. Zheng, S. Qiao*, et al. Nature Commun. 214, 5: 3783 (123 citations) Experiments: Synchrotron-based near edge X-ray adsorption fine structure Calculation: Density functional theory Combine experiments and calculation: There is a strong chemical interaction between g-c 3 N 4 and N-graphene, which promote the rapid electron transfer between two layers Y. Zheng, S. Qiao*, et al. Nature Commun. 214, 5: 3783. (123 citations) 14
High HER activity with low overpotential Tafel slope Robust stability in both acidic and alkaline solutions DFT calculation: Free energy diagram and volcano plot Combine experiments and calculation: Newly developed C 3 N 4 @NG non-metallic hybrid shows highly efficient hydrogen reduction and the activity is comparable with traditional metallic materials Y. Zheng, S. Qiao*, et al. Nature Commun. 214, 5: 3783 (123 citations) 3.2. HER P,N doped graphene catalysts Open up a new avenue for graphene materials electrochemical applications. Pave the way of heteroatoms doped graphene for electrocatalytic HER applications. A combined theoretical and experimental study. Theoretical prediction: Density functional theory N and P heteroatoms could coactivate the C in graphene to induce a synergistically enhanced reactivity toward HER Y. Zheng, S. Qiao*, et al. ACS Nano. 214, 8, 529-5296. (7 citations) 15
a Current Density (ma/cm 2 ) -2-4 -6-8.5 M H 2 SO 4 Graphite P-graphene N-graphene N,P-graphene-1-1 -.6 -.5 -.4 -.3 -.2 -.1 Potential vs. RHE (V) b HER Overpotential (V).6.55.5.45.4.35 Graphite (26 mv/decade) P-graphene (133 mv/decade) N-graphene (116 mv/decade) N,P-graphene-1 (91 mv/decade) -2.5-2. -1.5 Log I (A/cm 2 ) 3.2. HER P,N doped graphene catalysts Highly active HER Synergistic effect Better than single doped graphene Applicable in both acid and base solutions e i (A/cm 2 ) 3x1-7 i in.5 M H 2 SO 4 i *1 in.1 M KOH 2x1-7 1x1-7 f G 1-6 P-G N,P-G-1 1-8.5 M H 2 SO 4 1-1 I (A/cm 2 ) A good consistence of theoretical prediction and experimental verification P-G N,P-G-1 1-12.1 M KOH..4.8 1.2 1.6 2. G H* (ev) Y. Zheng, S. Qiao*, et al. ACS Nano. 214, 8, 529-5296. (7 citations) 5. Summary 1. Mesoporous and macroporous g-c3n4/c composite metal-free catalysts have high ORR activity, excellent stability and very high reaction efficiency. 2. Dual non-metal elements doped graphenes have a synergistic coupling effect which leads to enhanced ORR catalytic activity. 3. Metal-free electrocatalysts are also developed for Oxygen Evolution Reaction (OER) and Hydrogen Evolution Reaction (HER). Review & Feature Articles Chem Soc Rev, 215, 44, 26-286. (34 citations) Angew Chem, 215, 54, 52-65. (46 citations) Energy & Environmental Science, 212, 5, 6717-6731. (327 citations) Small, 212, 8, 355-3566. (22 citations) 16
Acknowledgement $$$ Australian Research Council $$$ The University of Queensland $$$ The University of Adelaide $$$ Industrial partners Thank you for your attention! 17