Tuning thermoelectric performance of π-d conjugated nickel ...
Nickel Sulfide Nanocrystal Synthesis Using Substituted ... · Nickel Sulfide Nanocrystal Synthesis...
1
Nickel Sulfide Nanocrystal Synthesis Using Substituted Thiophenols Joe Veglak 1,2 , Jordan Rhodes 1 & Janet Macdonald 1 1 Department of Chemistry, Vanderbilt University, Nashville, TN 2 Department of Chemical Engineering, Rose-Hulman Institute of Technology, Terre Haute, IN Introduction 20 25 30 35 40 45 50 55 60 65 70 Intensity (A.U.) 2θ (Degrees) Polydymite (Ni3 S4) 20 25 30 35 40 45 50 55 60 65 70 Intensity (A.U.) 2θ (Degrees) Heazlewoodite (Ni3 S2) Sulfur reagents used in this synthesis: A 1:1 ratio of Ni:S eliminated the thermodynamically stable millerite phase (NiS) consistently found creating mixed phase products when larger quantities of sulfur were present. • Oleylamine was used as the solvent of the reaction, its steric effects are used to help control particle size. • The para-substituted thiophenol was injected into the nickel solution at 170°C, to form a precursor phase, then heated to 220°C to form the desired phase. Phase Characterization 20 25 30 35 40 45 50 55 60 65 70 Intensity (A.U.) 2θ (Degrees) Heazlewoodite (Ni3 S2) Polydymite (Ni3 S4) EWG EDG ܥെ ܪଶ െ ܪܥଷ െ X-Ray Diffraction (XRD) was used to analyze the phase composition of each of the particles. Sulfur rich nickel sulfide phases correlated to substituted thiophenols with the less electron donating groups. Potential Phases: • Starting Material (NiCl ଶ ) • Heazlewoodite (Ni ଷ S ଶ ) • Polydymite (Ni ଷ S ସ ) Nickel Oxidation States: Ni ାଶ Ni ା Ni ା Ni ାଶ Ni ାଷ Ni ାଷ Ni ାଶ Electron donating groups are able to donate electrons to the nickel atoms, lowering nickel’s oxidation state, while electron withdrawing groups take electrons and raise the oxidation state. 100 nm A 20 nm Cl HS D 50 nm C 20 nm B Phase Cl Polydymite (Ni ଷ S ସ ) – 100% CH ଷ Polydymite (Ni ଷ S ସ ) – 71.6% Heazlewoodite (Ni ଷ S ଶ ) – 28.4% OCH ଷ Polydymite (Ni ଷ S ସ ) – 52.9% Heazlewoodite (Ni ଷ S ଶ ) – 47.1% NH ଶ Heazlewoodite (Ni ଷ S ଶ ) – 100% • Transmission Electron Microscopy (TEM) was used to obtain these images. • A-D decreases in terms of electron donating groups, A being the most electron donating and D being the least. • A larger surface area to volume ratio (smaller particles with more edges) typically makes for a better catalyst . Testing Catalytic Ability TEM images taken by Jordan Rhodes Future Direction and Conclusion Acknowledgements I would like to thank the National Science Foundation (NSF) for funding my work in the Macdonald lab, The VINSE NSF REU grant: 1560414, The VINSE program and staff, And all the members of the Macdonald lab Electron Donating Group (EDG) Electron Withdrawing Group (EWG) Bruice, P. Y. (2004). Organic Chemistry 6 th Edition. Upper Saddle River, NJ: Pearson/Prentice Hall -0.006 -0.004 -0.002 0 0.002 0.004 0.006 0.008 -0.5 -0.45 -0.4 -0.35 -0.3 -0.25 -0.2 -0.15 -0.1 -0.05 0 Current (mA) Voltage (vs. Ag/AgCl) (V) -CH3 -OCH3 -Cl -NH2 We have developed a facile synthesis of nickel sulfide nanocrystals through hot injection that demonstrates phase control by varying the substituent group of para-substituted thiophenols. In the future, we look to further test and enhance the particles catalytic abilities and test to see if the ligands on the particles are surface or crystal bound. Crystal bound ligands are far more desirable as catalysts because they leave the metal sites of nanocrystals exposed, the catalytically active centers. Additionally crystal bound ligands are more tightly bound and less likely to break. The ligands won’t contaminate the reaction solution. Turo M.J. Macdonald M.E., ACS Nano, 2014, 8 (10), pp 10206 Different phases and morphologies can largely effect the catalytic abilities of nickel sulfide nanocrystals. While nickel sulfides contain an abundance of different phases, phase control of these crystals can be difficult. One proposed method of selectively isolating these phases involves manipulating the sulfur reagent used, where the electron donating ability of substituent groups influences the reactivity of the sulfur precursor. Para-substituted thiophenols were used as the sulfur for this work. Preliminary Linear Sweep Voltammetry in a Hydrogen Evolution Reaction (HER) was used to test the particles’ catalytic ability Image created by Jordan Rhodes Synthetic Process Morphological Characterization Proposed hypothesis for phase change: A more positive voltage when the current drops indicates particles with better catalytic abilities. While the results are preliminary and thus inconclusive, there is already a possible trend showing particles formed using more electron donating substituent groups have greater catalytic abilities.
Transcript of Nickel Sulfide Nanocrystal Synthesis Using Substituted ... · Nickel Sulfide Nanocrystal Synthesis...
Nickel Sulfide Nanocrystal Synthesis Using Substituted ThiophenolsJoe Veglak1,2, Jordan Rhodes1 & Janet Macdonald1
1 Department of Chemistry, Vanderbilt University, Nashville, TN2 Department of Chemical Engineering, Rose-Hulman Institute of Technology, Terre Haute, IN
Introduction
20 25 30 35 40 45 50 55 60 65 70
Inte
nsity
(A.
U.)
2θ (Degrees)
Polydymite (Ni3 S4)
20 25 30 35 40 45 50 55 60 65 70
Inte
nsity
(A.
U.)
2θ (Degrees)
Heazlewoodite (Ni3 S2)
Sulfur reagents used in this synthesis:
A 1:1 ratio of Ni:S eliminated the thermodynamically stablemillerite phase (NiS) consistently found creating mixedphase products when larger quantities of sulfur werepresent.
• Oleylamine was used as thesolvent of the reaction, its stericeffects are used to help controlparticle size.
• The para-substituted thiophenolwas injected into the nickelsolution at 170°C, to form aprecursor phase, then heatedto 220°C to form the desiredphase.
Phase Characterization
20 25 30 35 40 45 50 55 60 65 70
Inte
nsity
(A.
U.)
2θ (Degrees)
Heazlewoodite (Ni3 S2)Polydymite (Ni3 S4)
EWG
EDG
X-Ray Diffraction (XRD)was used to analyze thephase composition ofeach of the particles.
Sulfur rich nickel sulfide phases correlated to substituted thiophenols with the less electron donating groups.
Potential Phases:
• Starting Material (NiCl )
• Heazlewoodite(Ni S )
• Polydymite(Ni S )
Nickel Oxidation States:NiNi Ni NiNi Ni NiElectron donating groups are able to donateelectrons to the nickel atoms, lowering nickel’soxidation state, while electron withdrawing groupstake electrons and raise the oxidation state.
100 nm
A
20 nm
Cl
HS
D
50 nm
C
20 nm
B
Phase Cl Polydymite
(Ni S ) – 100%CH Polydymite (Ni S ) – 71.6%Heazlewoodite(Ni S ) – 28.4%OCH Polydymite (Ni S ) – 52.9%Heazlewoodite (Ni S ) – 47.1%NH Heazlewoodite (Ni S ) – 100%
• Transmission ElectronMicroscopy (TEM) wasused to obtain theseimages.
• A-D decreases interms of electrondonating groups, Abeing the most electrondonating and D beingthe least.
• A larger surface area tovolume ratio (smallerparticles with moreedges) typically makesfor a better catalyst .
Testing Catalytic AbilityTEM images taken by Jordan Rhodes
Future Direction and Conclusion
AcknowledgementsI would like to thank the National Science Foundation (NSF) for funding my work in the Macdonald lab,The VINSE NSF REU grant: 1560414,The VINSE program and staff,And all the members of the Macdonald lab
Electron Donating Group (EDG)
Electron Withdrawing Group (EWG)
Bruice, P. Y. (2004). Organic Chemistry 6th Edition. Upper Saddle River, NJ: Pearson/Prentice Hall
-0.006
-0.004
-0.002
0
0.002
0.004
0.006
0.008
-0.5 -0.45 -0.4 -0.35 -0.3 -0.25 -0.2 -0.15 -0.1 -0.05 0Curr
ent
(mA)
Voltage (vs. Ag/AgCl) (V)
-CH3
-OCH3-Cl-NH2
We have developed a facile synthesis of nickel sulfide nanocrystalsthrough hot injection that demonstrates phase control by varying thesubstituent group of para-substituted thiophenols. In the future, we look tofurther test and enhance the particles catalytic abilities and test to see if theligands on the particles are surface or crystal bound.
Crystal bound ligands are far moredesirable as catalysts because theyleave the metal sites of nanocrystalsexposed, the catalytically active centers.Additionally crystal bound ligands aremore tightly bound and less likely tobreak. The ligands won’t contaminate thereaction solution.Turo M.J. Macdonald M.E., ACS Nano, 2014, 8 (10), pp 10206
Different phases and morphologies can largely effect thecatalytic abilities of nickel sulfide nanocrystals. While nickelsulfides contain an abundance of different phases, phasecontrol of these crystals can be difficult. One proposed methodof selectively isolating these phases involves manipulating thesulfur reagent used, where the electron donating ability ofsubstituent groups influences the reactivity of the sulfurprecursor. Para-substituted thiophenols were used as thesulfur for this work.
Preliminary Linear SweepVoltammetry in a HydrogenEvolution Reaction (HER)was used to test theparticles’ catalytic ability
Image created by Jordan Rhodes
Synthetic Process Morphological Characterization
Proposed hypothesis for phase change:
A more positive voltage when the current drops indicates particles with better catalytic abilities.
While the results are preliminary and thus inconclusive, there is already a possible
trend showing particles formed
using more electron donating substituent groups have greater
catalytic abilities.
