Hot Electron Chemistry at Solid-Liquid Interfaces

Hot Electron Chemistry at Solid‐Liquid Interfaces

Kirsten A. Louthan, Wens‐Tung Huang, Robert J. Hamers, Gilbert N. Nathanson, J.R. Schmidt

Department of Chemistry University of Wisconsin‐Madison 1101 University Avenue Madison, WI 53706 ([email protected]) Ph: 608‐262‐6371 High-Energy and Solvated Electrons in Water

e*- (high energy electrons)

H2O H2O H (>7 eV) H∙ + ∙OH 2 2H∙ + ∙O∙ Energetic H + ·O· (>6 eV) H O - Dissociation 2 2 2 (> 6 eV) H + ∙OH Reactions

H2O CH3OH ∙OH + H O+ H O+ 2H + CO (> 8 eV) 3 2 Ionization 2 (> 7 eV) Relaxation (<1 ps for H2O) e - H O - s e - 2 - H2 + 2OH s H∙ + OH 10 (slow, 20/M/s) (fast, 10 /M/s) H+ ROH H H H∙ H∙ + RO- 2 2 (fast) (moderate, 104/M/s) O2 O2 R-X H+ ∙O - R∙ + X- 2 10 9 HO2 (fast, 10 /M/s) (fast, 10 /M/s) (fast) + H CO2

N2 H∙ - hν CO2 - NH3 CO + O H∙ (fast, 1010/M/s) Emit electrons in the 10‐50 eV region to initiate novel chemistry Diamond as a (Negative Electron Affinity) electron emitter

‐7 Diamond ‐6

Evacuum ‐5 SHE

‐0 ‐4 e‐ + N2(g)  N2‐(aq) (est. ‐4.17 V) vs.

‐3 e‐ + H2O  e‐(aq) (‐2.86 V) ‐2 e‐ + H+  H (‐2.3 V) ‐2 ZrO SiC e‐ + CO  CO ‐ (‐1.9 V) 2 GaP Potential 2(aq) 2 (aq) TiO ‐1 ‐4 2 Si absolute) + 0 e‐ + H + e‐ 1/2 H2 (0 V) 1 (eV, O + 4H++ 4e‐ 2H O (+1.23)

E ‐6 2(g) 2 2

‐8 Diamond is capable of emitting electrons at energies that can enable entirely new reductive chemistry Solvated electrons

Reduction of N2 (nitrogen fixation) N2 + 3H2  2NH3 - Selective reduction of CO2 to CO, via one-electron pathway (CO2 radical anion) Why diamond and not glassy carbon, graphite, etc. ?

+ H reduction to H2 thermodynamically + H H2O 4 favorable

0 HHHH (mA) diamondCCCC ‐2 electrochemical grade

Current boron‐doped diamond ‐4 edge plane graphite diamond ‐2 ‐1 0 1 2 Potential (V vs Ag/AgCl)

+ • Large overpotential for H reduction and H2O oxidation  Catalyze difficult reactions with minimal inference from water

Diamond is a very promising materials for catalysis at potentials outside of the water stability window of ~ 0 to +1.23 V Diamond-water interface

Water 0.8 V -0 Conduction -4 Evacuum band 5.5 eV e‐ + H2O  e‐(aq) (‐2.86 V) -2 + -2 e‐ + H  H (‐2.3 V) ‐ e‐ + CO2(aq)  CO2 (aq)(‐1.9 V) 0.44 V -4 + ESHE 2e‐ + CO2(aq) +2H  H2O +CO (‐0.5 V) 0 SHE) vs. Potential (V E + F H + e‐ 1/2 H2 (0 V) CO +2H+ +2e‐ C + H O (+.8 V) Evb 2 -6 + 0.25 V O2(g) + 4H + 4e‐ 2H2O (+1.23) Electron emission from diamond in vacuum: Bulk and Surface pathways

Bulk absorption (I) Kinetic

energy ECB  Evac e‐ yield

EF EVB

Barrier‐free electron emission

In vacuum, diamond can act as a solid-state electron source

Physical Review Letters 78, 1803‐1806, 1997; Applied Surface Science, 168, 79‐84, 2000 Photocatalytic Reduction of N2 to NH3

-5 V ‐5 e‐ + N2(g)  N2‐(aq) (est. ‐4.17 V) -4 V  ‐ ‐4 N2H e‐ + N2 N2 + NHE e‐ + N + H  N H (est. ‐3.2 V) ‐ + 2(g) 2 (aq) -3 V N2 + H  N2H vs. ‐3 e‐ + H O  e‐ (‐2.86 V)

2 (aq) + + -2 V e‐ + H  H e‐ + H  H (‐2.3 V) ‐2 ‐ e‐ + CO2(aq)  CO2 (aq)(‐1.9 V) H+ N2  N2H -1 V ‐1 Potential N2H2 Potential vs NHE N2H4 + 0 V NHE0 H + e‐ 1/2 H2 (0 V) N2 1 V 1

2NH3 Why is this reaction so difficult?

1) N2 doesn’t stick well on catalyst surfaces 2) The high potential of the first step of reduction A potential solution 1) Use electron emission to eliminate need for surface adsorption 2) Use high energy of electrons to induce very difficult reactions

T. A. Bazhenova, A. E. Shilov, Coordination Chem. Rev., 1995, 144, 69. Photocatalytic reduction of N2 by solvated electrons

Boron-doped diamond Filter 8 (optional)

KI 6

N2-saturated 4

Water cell Diamond Platinum (absorbs IR) 2 Ar-saturated (control) Conduction dband 0 - e- + N2  N2 (aq) - 0 1 2 3 4 5 6 e- + H2O  e (aq) + e- + H  H(aq) Illumination Time (hours)

Valence 2H2O O2(g)+ Pt band 4H++4e- e-

Solvated electrons induce reduction of N2 to NH3 Nature Materials 2013, 12, 836-841 Does the reaction depend on diamond’s Negative Electron Affinity?

O-terminated H-terminated Diamond surface Diamond surface Positive electron affinity Negative electron affinity 4.0 H ‐ + + ‐   C O C H 3.0 C H C O yield C O C H 3 2.0 NH H

1.0 O H O O 0.0 E6 Electronic Diamond electrochemical Grade Powder grade diamond diamond

Photoelectron emission is strongly dependent on oxidation state of the surface.

 Only the surface with NEA property exhibits high yield for N2 reduction Surface chemistry controls the electron emission process Final reaction pathway

• Early steps: e- + H+  H – Dominated by H-atom addition

– (Competition with H2 production) N2 + H  N2H H + H  H2

• Later steps:

– Proceed via sequential protonation / + N2H5 + e-  N2H5 reduction by e-(aq) – (Rate limiting at low pH!)

• Cleavage of N-N bond is favorable at late N H +  NH + + NH stages 2 5 3 3

Involves both direct ET and reactive e-(aq) by-products Journal of Physical Chemistry B 2014, 118, 195-203 CO2 reduction

• Two‐compartment quartz cell within SS pressure vessel • Typically ~200 psi (15 atmospheres) • ‐0.5V bias is applied to diamond • Gas‐ and liquid‐phases analyzed after reaction

Infrared head‐space analysis

(CO, CO2, other gas‐phase products)

GC/MS, NMR, Ion Chromatography

(H2, Formate, other liquid‐phase products) Typical Analysis: • UV Fused CO = 100 micrograms Silica Window No detectable H2 (detection limit 5g) Formate: 28 micrograms

>95 % selectivity for CO product Solvated electrons and chemistry

CO production using isotopically labeled CO2

Products using natural 12 CO2 (99% CO2)

Products using 13 CO2

2200 2150 2100 2050 2000 13 13  CO2 produces only CO 12 12  CO2 (Natural abundance) produces only CO  Complete isotopic selectivity  (No side‐reaction of diamond oxidation) Why does this selectively reduce CO2 over protons ?

-5 -4

-3 e- + H2O  e-(aq) (-2.86 V) e- + H+  H• (-2.3 V) -2 - e- + CO2(aq)  CO2 (aq)(-1.9 V) -1 Potential vs. NHE

e-(aq) H+[6x10-4 M] H• Rate = 1.4 × 107 s-1 k = 2.3 × 1010 L mol-1 s-1

CO2 [0.8 M] - Rate = 6.2 × 109 s-1 CO2• k = 7.7 × 109 L mol-1 s-1

Rate modeling predicts 99.8% of solvated electrons form CO2•- and only 0.2% form H• Angewandte Chemie 2014, 53, 9746-9750 Solvated Electrons

Electrons in water are surrounded by e- a solvent cage of ~ 6 water molecules, forming “solvated” or “wet” electrons

Solvated electrons absorb in the visible, peaking near 720 nm at 300 K e-

632 nm e-

e- e- e-

100 nm

Diffusion coefficient 5x10‐5 cm2/sec Lifetime ~1 μs Diffusion length 100 nm Electrons should travel distances on 1) W. Gottachall and E. Hart, J. Phys. Chem., 1967,7,71,2106 2) Schmidt, K. H.; Han, P.;, J. Phys. Chem. 1992, 96, 199‐206. the order of ~ 100 nm in pure water Transient Absorption measurements of solvated electrons

Nd: YAG laser 4

Water with H2SO4 Tripler 213 nm UV 2 3 ns pulses OPO 0 Pure water ‐2 HeNe laser photodiode ‐4 e- e- e- h+ - + e + h + h+ h e- h ‐6 diamond Photodetector response (mV) 0 50 100 150 Time (ns) Challenges: • Sensitivity • Two‐photon electron emission from water (photochemical only) • Thermal/mechanical effects Prior Research: Creation and Reaction of Solvated Electrons at the Gas-Liquid Interface 57% of the H 43% of the H atoms form H2 Na H atoms desorb! 2 Gas Phase Na atoms ionize at the surface of protic liquids and N generate surface‐solvated electrons. a e- H These electrons readily react to Na+ Glycerol produce H atoms. Vacuum-Glycerol Interface

Na+ ‐ electron pair Na atom

0 ps – Na atom collision begins 10 ps – Na atom ionizes Alexander, Minton, Sankaran, Schatz, Wiens, Nathanson Science 335, 1072 (2012); JACS 2014, 136, 3065‐3074 A key intermediate: the solvated electron

The solvated electron has:

Reduction potential ‐2.9 V

Lifetime in (very) pure water of ~ 300 s, but more typically ~300 ns

e‐ + H2O  H + OH‐ (slow) ‐‐ e‐ + CO2  CO2 (fast) e‐ + H+  H (fast)

The solvated electron is the chemist’s perfect reducing agent Summary of Prior Work: Photo-excited diamond initiates new chemistry, including • Formation of solvated electrons

• Reduction of N2 to NH3 • Selective reduction of CO2 to CO

High overpotential for H+ reduction at diamond surface plays a key role in enabling higher-energy reactions

Goal of Current project

Electrically-induced emission of electrons from diamond should provide an energy-efficient route to production of solvated and hot electrons and other high-energy species in both aqueous and non-aqueous liquids Goals • Create hot electrons and solvated electrons in liquids by direct injection from diamond-coated field-emission tips and tip arrays • Investigate the use of hot/solvated electrons to electrochemically reduce solution-phase reactants. • Identify the nature of chemical intermediates formed as a result of the interaction of hot electrons with aqueous and non- aqueous media • Develop a theoretical understanding of hot-electron interactions with materials and the reaction pathways of the species produced.

We target the low-voltage field-emission regime (~10-50 eV) and the transition to low-energy “nano-plasmas” using both DC and pulsed fields. Exploring Elementary Electron Reactions in Vacuum

inject electrons from a diamond sleeve into the water jet Water Microjet (just 10 m diameter!)

Electron pulsed voltage Reactions in

Pure Water DO2

electron‐solute reactions

‐ ‐ + es  + Cl (evaporate) High-Energy and Solvated Electrons in Water

e*- (high energy electrons)

H2O H2O H (>7 eV) H∙ + ∙OH 2 2H∙ + ∙O∙ Energetic H + ·O· (>6 eV) H O - Dissociation 2 2 2 (> 6 eV) H + ∙OH Reactions

N2 H∙ - hν CO2 - NH3 CO + O H∙ (fast, 1010/M/s) Emit electrons in the 10‐50 eV region to initiate novel chemistry Transient absorption, emission spectroscopies

Source Monochromator i‐CCD

SiO2 V(t) ~ 5 nm gold Kapton., 25 m Diamond

V(t)

~ ns Quantum Chemical Reactivity Studies and Kinetic Modeling

Calculated rate Measured constants of e‐(aq), rate constants reactants, and of e‐(aq) reactive intermediates Kinetic model of reactivity • Rate constants Evaluate model estimated using (add reactions, etc.) electronic structure • Thermochemistry: G4, continuum Predicted solvation product yields • Barriers: CCSD(T) and distribution • Similar approach

used for N2 reduction Kinetic modeling reactivity of hot electrons: Applications

• Reactivity of hot vs. thermal electrons

‐ e‐* + CH3OD → CH3O + D* (production of hot D*) D* + CH3OD → D2 + CH3O∙ Dthermal + CH3OD → HD + CH23OD Kinetic models will allow prediction of product branching ratio as a function of D* vs. Dthermal • Reaction pathways of degradation of halogenated molecules e‐ + R‐X → R∙ + X‐ e‐ + H2O → → H∙, OH∙ … H∙ + R‐X → R∙ + HX

Direct vs. indirect degredation of halogenated molecules Modeling relaxation and thermalization of hot electrons

• Hot electron relaxation modeled with real‐ time time‐dependent density functional theory (RT‐TDDFT) –watches evolution of initial excited state in real time

• Prior work has focused on low energy relaxation of solvated electrons • Little work on relaxation of hot (conduction band) electrons

• Prior evidence for energy‐dependent relaxation • Examine relaxation to:

• conduction band edge (k1) and • equilibrium solvation (k2) in • aqueous and non‐aqueous environments Model Systems

Mechanistic Studies of Hot Electrons in Aqueous and Degradation of Halogenated Non‐Aqueous Media and Biological Molecules

Electron‐Stimulated

Reduction of N2 to NH3 at Ambient Temperatures Destruction of Halogenated Waste by Electrons

Present Methods for Destruction of PCBs: *high temperature incinerators and cement kilns *landfill burial and temporary containment PCBs Emerging Technologies *Supercritical water oxidation

*Gas‐phase H2 reduction to methane *NaOH‐catalyzed destruction dioxins *Molten metal and molten salts Electron Technologies *Oxidation in an electrochemical cell *Solid sodium dissolved in liquid ammonia *Plasma discharges DDT ‐ *Solvated electrons from diamond? es e*‐ Electron Mechanism Mustard Gas e‐ + RCl  R + Cl‐ Model systems: Destruction of Halogenated Waste by Electrons

Present Methods for Destruction of PCBs: *high temperature incinerators and cement kilns *landfill burial and temporary containment Emerging Technologies *Supercritical water oxidation

*Gas‐phase H2 reduction to methane *NaOH‐catalyzed destruction *Molten metal and molten salts Electron Technologies *Oxidation in an electrochemical cell *Solid sodium dissolved in liquid ammonia *Plasma discharges *Solvated electrons from diamond? Electron Mechanism: Solvated Electrons! ‐ + Na(s) + NH3(liq)  es + Na ‐ ‐ es + RCl  R + Cl Reactions of OH and HO2 with Lipids

*‐ + + e (excited) + H2O H2O OH + H3O e‐ (solvated) + O ‐ O ‐ + H+ HO 2 O2 2 2

Linoleic Acid (LH)

H Abstraction Hydroperoxide Formation

- + OH, HO2 HO2, O2 + H ,O2 + LH Electron‐Driven Degradation of Cell Membranes for Destruction of Bacteria Progress thus far Approaches to High-energy electrons in water

Approaches

1) High‐field electron emission into liquids

2) High‐field electron emission into liquids

3) Planar 3‐terminal devices: the “water transistor” Photochemical vs. Electrochemical Photochemical Electrical (Past work) (New effort)

ECB, bulk e‐ E light F, electrode ECB, bulk EF, diamond EF, diamond

EVB, bulk Water , anode E E N-doped (n-type) VB, bulk F, anode diamond cathode N-doped (n-type) Water Metallic diamond cathode anode Conduction‐band electrons created Conduction‐band electrons created by excitation with Ephoton>5.5 eV by injection from metallic substrate • Need deep UV photons • Use field‐enhancement • Diamond only a weak absorber • n‐type diamond (electrons are (indirect‐gap semiconductor) majority carriers) • Field‐free emission only for p‐type diamond Trapezoidal barrier (metal) vs. barrier-free (diamond) emission metal diamond

ECB Evacuum Evacuum , cathode EF EF

Metallic anode EVB, bulk  N-doped (n-type) , anode , anode diamond cathode Water Water EF, anode EF, anode

Metallic Metallic anode anode

Electron emission by field emission No barrier for electrons in the or thermionic emission processes diamond conduction band due to  Must overcome a barrier diamond’s NEA  Must get electrons into CB (!) Generating Solvated Electrons via Diamond Films for Chemical Reactions in Water

Diamond

Platinum ‐ e‐ e e- - e‐ e e‐ ‐ e e‐ (aq) Niobium

- e- e Reaction battery

Emission Solvation • Reduction of CO2 to CO

• N2NH3 : Ammonia Production • Destruction of Hazardous Waste e‐ e‐ • Sterilization  Degradation of Cell Membranes Electron Emission from Diamond: A New Paradigm for Catalysis in Water

Traditional Electrocatalysis: Solvated Electrons: Reactions Occur at Electrode Surface Reactions Occur in Solution e‐

OH H H HH H H HH H Traditional e‐ Diamond Electrode

e‐ Transformation of Nitrogen into Ammonia

‐ N2 + 6 e NH3 Bacteria Degradation Linoleic Acid (LH) Dechlorination ‐ DDT e e‐ ‐ Cl• ‐ Cl•

e‐ Diamond Cell Components N2 gas Pt wire leading in and out to Pt mesh Pt e- mesh Diamond film on Niobium

e‐ e‐ 0.1 M 10 mL Na2SO4 8 mm e‐ ‐ solution e copper tape Attached to Pt mesh 2 cm2 area Nb surface e-

Scanning Electron Microscope diamond electrode assembly

microwave plasma 1 μm ‐assisted CVD chamber (1 SCCM CH4 + 200 SCCM H2 at 48 Torr and 800 watts for 2 hours) Current‐Voltage (Tafel) Plot for (nominally) Undoped Diamond

50 mA

0.1 M Na2SO4 e- (current) scan rate = 50 mV/sec

low voltage, low current e‐ e‐ 0.1 M Na2SO4 Voltage ‐ (< 1 μA) e e‐

e- + Indophenol Blue Method for Detecting NH3/NH4

2 + 2NH + 3ClO‐ ‐ 3 +H2O+ 3Cl salicylate blue dye

indophenol method

Nessler method

Absorbance

Fit

Calibrated with NH4Cl(aq) + Nessler method for Detecting NH3/NH4

Absorbance indophenol method

Fit

Nessler method From Battery Electrons to Solvated Electrons?

Producing NH3 from N2 Without Light or Heat

Battery-Initiated Synthesis of Ammonia!

1.6 9×10‐8 moles 1 atm N2 1.4 - N2 + 6es 2NH3

0.1 M g) 1.2 e‐ e‐ Na2SO4 μ (

1 ‐ e e‐ 0.8 4×10‐8 moles 0.6 0.4

Ammonia 0.2 0 blank 0V ‐8V 4hours 4hours contamination/calibration/(electro)chemical reaction? Hydrogen Termination Promotes NH3 Production

‐2 V applied voltage H‐terminated Hydrogen 0‐4 hours oxygen termination terminated 0‐4 hour ozone lamp

terminate again partially oxygen With H2 plasma terminated

hydrogen termination

8‐12 hours 4‐8 hours Directions for Coming Year

*Increase ammonia yield by utilizing high pressure N2 in steel cell

*Explore reduction of CO2 to CO

*Directly detect solvated electrons

CCD

V(t) Approaches to High-energy electrons in water

Approaches

1) High‐field electron emission into liquids

2) High‐field electron emission into liquids

3) Planar 3‐terminal devices: the “water transistor” The simplest incarnation DC or pulsed ~ 5 – 100 V ~ns to microsecond ‐ +

I R

Tip-solution Diamond-coated Aqueous Counter- Tip-solution-plate Field Emitter Medium electrode Parallel “forests” of emitters in 2-dimensional plate Approach

Fabrication and Testing of Diamond-Coated Electron Emitters • Individual nanoscale emitters • Forests of nanoscale emitters by RIE etching of diamond • Forests of emitters by deposition onto nano-templated electrodes Reactions in Ambient Static Samples and in Vacuum- Based Microjets • Electrical Response, optical emission/absorption • Real-time product detection via mass spec Quantum Chemical Reactivity Studies and Kinetic Modeling Nanoscale diamond-coated tips

“UNCD” growth methodsN-doping Getting the electrons out: n‐type diamond

At equilibrium n‐type diamond With applied field, diamond will have has upward band‐bending downward band‐bending

 Evacuum ECB, surface ‐ ‐ e e Evacuum ECB, bulk ECB, bulk , anode EF, cathode EF, cathode EF, anode

Vapplied Metallic anode EVB, bulk EVB, bulk , anode EF, anode

N-toped (n-type) Water N-doped (n-type) Water Metallic diamond cathode diamond cathode anode At diamond‐aqueous interface it should be possible to use an applied field to achieve downward band‐bending and facile electron emission n‐type diamond should be a facile emitter of electrons into water with a suitable negative bias applied How do we think of the emission of low-energy electrons at the diamond-water interface? What is the role of mid-gap states due to surface termination? • C-H antibonding •C=O * states Making forests of diamond nano-tips by reactive ion etching

CVD diamond thin film Oxygen reactive ion etching After RIE, top view

After RIE, tilted view Forest of diamond nano-tips Steps in arc formation

Electron field emission  Solvated electrons  Dissociation products

Secondary ionization, “Streamer” formation

Bubble nucleation Arc formation

Need to control voltage, time to eject electrons without forming streamers, arcs

Jones and Kunhardt, J. Appl. Phys. 1995, 78, 3310. Time constant for electrode-electrolyte interface

electrode electrolyte

CDL RS

1M KCl, bulk resistivity r~ 5 ohm-cm: Time constant ~ ns

25 mm electrode spacing, 1 cm2 area  R=0.012 ohm Double-layer capacitance ~ 20 F/cm2 ? For 1 cm2 area, C~ 20 mF RC ~ 250 nanoseconds Approaches to High-energy electrons in water

Approaches

1) High‐field electron emission into liquids

2) High‐field electron emission into liquids

3) Planar 3‐terminal devices: the “water transistor” Another approach: metal-insulator-water junction Thin Thin electrode insulator water electrode insulator water

Some prior investigations, mostly investigating electrical leakage in

electrolytic capacitors (Al‐Al2O3‐H2O)

Challenge: H+, Na+ diffusion through thin oxide layers Our approach: n‐‐‐Si (metal)‐GaN‐water ‐‐ n ‐Si (metal) ‐SiO2‐water “Metal”‐Insulator‐Water” junction (A)

(nA)

Current Current

Buildup of static charge shifts open‐circuit potential Strong asymmetry in I‐V response, typical response for rectifying semiconductor junction thin

~95% sufficiently

101

base

n C the

m ~5% 

<1 p B base traverse t

n E idea:

Key Electrons transistors

C I ~95% C +

I d Bipolar n BC V B B I I p BC ~5% n + E EB E I V E I Two approaches to the “base”

 Insulator tbase<5 m ++ Electrode (n ‐Si)(SiO2, GaN)Au water

E B C ~95%

~5% graphene Electrode (n++‐Si)insulator water

E B C ~95%

~5% Inelastic mean free paths

In the ~10 V range, IMFPs can be ~ 2 nm in gold and other metals. path

free A few‐nm coating can fix the surface

mean potential while allowing electrons to be

(Angstroms) injected through the metal film.

Inelastic Thin Kinetic energy (eV) electrode insulator water

E B C path

free ~95% mean

++ ~5%

(Angstroms) N Silicon GaN ~few nm tbase<1 m Or water Au SiO2 Inelastic Kinetic energy (eV) The “Water transistor”

Si GaN Au Water

IB IB + IE + IC (mA) IC IE VEB VBC= ‐ 0.5 V Current A “water transistor” with a current gain of ~5 ~15 mA of electron injection into water

Vemitter‐base *These results are very preliminary. Still need to verify that currents are from electron injection into water and conventional surface reduction reactions An improved version: graphene base

E C Si electrode

n++ Silicon GaN graphene water or

SiO2 73% transmission per monolayer @ 66 eV kinetic energy1

Longchamp, Latychevskaia, Escher, and Fink, Appl. Phys. Lett. 2012, 101, 113117 Making the metal-insulator-graphene sandwich

Au ring (contact) GaN(insulator) Si(metal)

Etch Cu Spin‐coat PMMA

Transfer Remove PMMA (toluene) Summary

• Preliminary data indicate ability to reduce N2 to NH3 at modest voltages, implying solvated electron or H‐atom intermediates

• Novel two‐ and three‐electrode devices (“water transistor”) are being developed with the possibility of injecting eletrons directly into water at modest voltages.

• The “pre‐plasma” region represents a potentially energy‐efficient route to making a wide range of novel radical species and excited states without high voltage

• We aim to study the distribution of non‐thermal products using both experimental and computational approaches

• Model systems will investigate the use of solvated electrons and other species to induce breakdown of halogenated compounds and to degrade model lipids. Acknowledgments

Wen Huang Kirsten Louthan

Di Zhu (electron emission, N2) Jason Bandy (Diamond thin films)

Linghong Zhang (CO2)

References: Nature Materials 2013, 12, 836-841 Journal of Physical Chemistry B 2014, 118, 195-203 Angewandte Chemie 2014, 53, 9746-9750