2010 Spring Symposium

 
Jing­guang G. Chen
Cen­ter for Cat­alyt­ic Sci­ence and Tech­nol­o­gy
Depart­ment of Chem­i­cal Engi­neer­ing
Uni­ver­si­ty of Delaware
Newark, DE 19716

Abstract — Met­al car­bides [1–3] and bimetal­lic alloys [4–7] often show nov­el cat­alyt­ic and elec­tro­cat­alyt­ic prop­er­ties. How­ev­er, it is dif­fi­cult to know a pri­ori how the chem­i­cal prop­er­ties of par­tic­u­lar car­bide and bimetal­lic sys­tems will be mod­i­fied rel­a­tive to the par­ent met­als. In the past few years our research group has inves­ti­gat­ed the nov­el cat­alyt­ic prop­er­ties of var­i­ous car­bide and bimetal­lic sys­tems, using a com­bi­na­tion of Den­si­ty Func­tion­al The­o­ry (DFT) cal­cu­la­tions, sur­face sci­ence stud­ies on sin­gle crys­tal sur­faces, and reac­tor and fuel cell stud­ies of sup­port­ed cat­a­lysts. The gen­er­al trends from the exper­i­men­tal and the­o­ret­i­cal stud­ies of car­bide [1] and bimetal­lic sur­faces [4] have been sum­ma­rized in recent reviews.

In this talk we will describe the uti­liza­tion of tung­sten car­bides as poten­tial anode elec­tro­cat­a­lysts for Direct Methanol Fuel Cells (DMFC). Cur­rent­ly, the anode elec­tro­cat­a­lysts for DMFC are Pt and Pt/Ru, which are dis­ad­van­ta­geous in terms of the pro­hib­i­tive­ly high costs and their sus­cep­ti­bil­i­ty to be poi­soned by CO. We will describe how to con­trol the decom­po­si­tion path­ways of methanol on sin­gle crys­tal sur­faces of tung­sten car­bides under well-con­trolled ultra­high vac­u­um (UHV) con­di­tions. We will also dis­cuss the syn­the­sis of phase pure tung­sten car­bide elec­trodes using Phys­i­cal Vapor Depo­si­tion (PVD) to bridge the “mate­ri­als gap” between sin­gle crys­tal sur­faces and poly­crys­talline films. We will then present our results of the elec­tro­chem­i­cal eval­u­a­tion of the tung­sten car­bide elec­trodes to bridge the “pres­sure gap” between UHV envi­ron­ment and elec­tro­chem­i­cal con­di­tions. We will also briefly dis­cuss the ther­mo­dy­nam­ic sta­bil­i­ty and kinet­ic mea­sure­ments regard­ing the bimetal­lic sur­faces in the pres­ence of oxy­gen under both UHV [8] and atmos­pher­ic [9] con­di­tions, which should help iden­ti­fy active and sta­ble bimetal­lic cath­ode elec­tro­cat­a­lysts in the Oxy­gen Reduc­tion Reac­tion (ORR) in fuel cells.

[1] Hwu & Chen, Chem­i­cal Reviews, 105 (2005) 185–212.
[2] Na, Zhang, Zheng, Wang & Chen, Angew. Chem. Int. Ed. 47 (2008) 8510.
[3] Weigert, Stot­tle­my­er, Zell­ner & Chen, J. Phys. Chem. C, 111 (2007) 14617.
[4] Chen, Men­ning & Zell­ner, Sur­face Sci­ence Reports, 63 (2008) 201–254.
[5] Hwu, Eng & Chen, J. Am. Chem. Soc. 124 (2002) 702.
[6] Kitchin, Norskov, Barteau & Chen, Phys. Rev. Lett. 93 (2004) 156801.
[7] Muril­lo, Goda & Chen, J. Am. Chem. Soc. 129 (2007) 7101.
[8] Men­ning & Chen, J. Chem. Phys. 130 (2009) 174709.
[9] Men­ning & Chen, J. Pow­er Sources, 195 (2010) 3140.

Speaker’s Biog­ra­phy — Jing­guang Chen is the Claire D. LeClaire Pro­fes­sor of chem­i­cal engi­neer­ing. He also holds the posi­tions of the Inter­im Direc­tor of the Uni­ver­si­ty of Delaware Ener­gy Insti­tute and Co-Direc­tor of the Ener­gy Fron­tier Research Cen­ter at the Uni­ver­si­ty of Delaware. He received his Ph.D. degree from the Uni­ver­si­ty of Pitts­burgh 1988. He spent one year in Ger­many as a Hum­boldt Post­doc­tor­al Fel­low before start­ing his career at the Exxon Cor­po­rate Research Lab­o­ra­to­ries. In 1998 he accept­ed a fac­ul­ty posi­tion at the Uni­ver­si­ty of Delaware and served as the Direc­tor of the Cen­ter for Cat­alyt­ic Sci­ence and Tech­nol­o­gy (CCST) from 2000–2007. He has 200 jour­nal pub­li­ca­tions and 17 US patents. He is very active in serv­ing the sur­face sci­ence and catal­y­sis com­mu­ni­ties, includ­ing respon­si­bil­i­ties as the Chair for the Gor­don Research Con­fer­ence on Catal­y­sis in 2002, the Chair of the Philadel­phia Catal­y­sis Club in 2004, the Catal­y­sis Sec­re­tari­at of the Amer­i­can Chem­i­cal Soci­ety in 2007, and the Board of Direc­tors for the North Amer­i­can Catal­y­sis Soci­ety. He is also the co-founder and team leader of the first Syn­chro­tron Catal­y­sis Con­sor­tium in the US for the Depart­ment of Ener­gy.

2010 Spring Symposium

 
George J. Antos
Direc­tor, Catal­y­sis and Bio­catal­y­sis Pro­gram
Direc­torate for Engi­neer­ing
Nation­al Sci­ence Foun­da­tion


Abstract — Catal­y­sis played an impor­tant role in the devel­op­ment of the petro­le­um-derived fuel indus­try into the key part of the world­wide indus­tri­al pic­ture that it is today. For var­i­ous strate­gic rea­sons, a new fuel plat­form based on bio­mass is desired to sup­ple­ment and replace the petro­le­um of today. Corn-derived ethanol from fer­men­ta­tion was the first move­ment. Addi­tion­al tech­nol­o­gy is seen to be nec­es­sary how­ev­er. Where can we seek the tools nec­es­sary to achieve ambi­tious petro­le­um-replace­ment goals? Recent advances in catal­y­sis and bio­catal­y­sis hold great promise for new path­ways to the mass pro­duc­tion of next gen­er­a­tion hydro­car­bon bio­fu­els: green gaso­line, diesel and jet fuel from switch­grass, for­est waste, and agri­cul­tur­al residue. The poten­tial advan­tages of hydro­car­bon pro­duc­tion from lig­no­cel­lu­losic feed­stocks will be dis­cussed, and the newest process path­ways and catal­y­sis impacts will be out­lined. Com­mer­cial­iza­tion efforts will be dis­cussed. Yet gaps in knowl­edge still exist. Fed­er­al fund­ing oppor­tu­ni­ties in hydro­car­bon bio­fu­els will be touched on.

Speaker’s Biog­ra­phy — Dr. George J. Antos is cur­rent­ly the Direc­tor of the Catal­y­sis and Bio­catal­y­sis Pro­gram in the Engi­neer­ing Direc­torate at the Nation­al Sci­ence Foun­da­tion. This pro­gram receives 150–200 pro­pos­als for uni­ver­si­ty research fund­ing in fun­da­men­tal catal­y­sis, bio­catal­y­sis, bio­mass con­ver­sion, elec­tro­catal­y­sis and pho­to­catal­y­sis each year with mil­lions of dol­lars award­ed annu­al­ly. George joined NSF after a 33+ year career in indus­try with UOP LLC. This expe­ri­ence encom­passed the research, devel­op­ment and com­mer­cial­iza­tion of process, cat­a­lyst and mate­r­i­al tech­nolo­gies for the petro­le­um refin­ing and petro­chem­i­cal indus­tries. George has authored and co-authored over 160 US patents, and has develped a large num­ber of pre­sen­ta­tions and papers in the area. George is also an Adjunct Pro­fes­sor with the Chem­i­cal and Bio­log­i­cal Engi­neer­ing Depart­ment at the Uni­ver­si­ty of Wis­con­sin, Madi­son and is CEO of Cat­a­lyst Real­iza­tions, Inc., a con­sult­ing com­pa­ny. His edu­ca­tion includes a B.S. in Chem­istry from Iowa State Uni­ver­si­ty, and M.S. and Ph.D. degrees in Chem­istry from North­west­ern Uni­ver­si­ty.

2010 Spring Symposium

 
Alessan­dro Fal­di
Exxon­Mo­bil Research & Engi­neer­ing Com­pa­ny
1545 Route 22 East
Annan­dale, NJ 08801
Alessandro.​Faldi@​ExxonMobil.​com


The pre­sen­ta­tion first high­lights ExxonMobil’s Out­look for Ener­gy, which reflects an assess­ment of glob­al sup­ply and demand through 2030 based on the under­ly­ing fac­tors that are shap­ing impor­tant ener­gy chal­lenges around the world. As always, the Out­look for Ener­gy focus­es on sev­er­al key areas of inter­est, which this year will include grow­ing trans­porta­tion and pow­er gen­er­a­tion demands as well as the out­look for ener­gy-relat­ed CO₂ emis­sions.

Eco­nom­ic progress and grow­ing pop­u­la­tions, espe­cial­ly in devel­op­ing coun­tries, will dri­ve ener­gy demand approx­i­mate­ly 35% high­er in 2030 ver­sus 2005. This demand increase is antic­i­pat­ed despite sub­stan­tial effi­cien­cy gains, which are expect­ed to accel­er­ate as new tech­nolo­gies are devel­oped and deployed.

Ris­ing trans­porta­tion needs will increase relat­ed ener­gy require­ments approx­i­mate­ly 40% by 2030, even as light-duty vehi­cles with much bet­ter fuel econ­o­my pen­e­trate the mar­ket. The rise in trans­porta­tion demand will be met pri­mar­i­ly by oil, which will pro­vide close to 95 per­cent of all trans­porta­tion fuels in 2030.

As economies grow, glob­al demand for elec­tric­i­ty is pro­ject­ed to increase 75 per­cent by 2030. Con­sis­tent with this pro­jec­tion, ener­gy for pow­er gen­er­a­tion is expect­ed to remain the largest and fastest grow­ing seg­ment of glob­al demand, dri­ven in large part by increas­es in Asia Pacif­ic. Meet­ing the expect­ed world­wide growth in pow­er demand will require a diverse set of ener­gy sources. Today coal is dom­i­nant and will retain the largest share glob­al­ly through 2030; how­ev­er, nat­ur­al gas, nuclear, and renew­ables will all gain mar­ket share.

In the sec­ond part of my talk, I’ll describe that meet­ing this ener­gy demand requires an inte­grat­ed set of solu­tions, includ­ing expand­ing all types of sup­ply, improv­ing effi­cien­cy, and mit­i­gat­ing green­house gas emis­sions. I’ll touch on exam­ples of how tech­nol­o­gy will play a crit­i­cal role in meet­ing these chal­lenges, and dis­cuss ExxonMobil’s alliance with a lead­ing biotech com­pa­ny, Syn­thet­ic Genomics Inc., to research and devel­op next gen­er­a­tion bio­fu­els from pho­to­syn­thet­ic algae.

Speaker’s Biog­ra­phy Alessan­dro Fal­di — Alessan­dro has a Lau­rea in Chem­i­cal Engi­neer­ing from the Poly­tech­nic of Milan, Italy, and a Ph. D. in Chem­i­cal Engi­neer­ing from the Uni­ver­si­ty of Min­neso­ta. He joined Exxon Chem­i­cal Com­pa­ny in 1994 as a research engi­neer at the Bay­town Poly­mers Cen­ter, Exxon Chem­i­cal Tech­nol­o­gy, where he held tech­ni­cal posi­tions in mate­ri­als char­ac­ter­i­za­tion, advanced char­ac­ter­i­za­tion and prod­uct devel­op­ment.

In 2000, Alessan­dro moved to Exxon­Mo­bil Chemical’s head­quar­ters in Hous­ton, Texas where he held mar­ket plan­ner and mar­ket devel­op­ment posi­tions in the Polypropy­lene busi­ness.

In 2005, Alessan­dro returned to Chemical’s Tech­nol­o­gy in Bay­town, Texas to become Pro­gram Leader of a break­through team that devel­oped advan­taged tech­nol­o­gy for Exxon­Mo­bil Chemical’s spe­cial­ty busi­ness.

In 2007, he was appoint­ed Cor­po­rate Pro­grams Port­fo­lio Man­ag­er in Cor­po­rate Strate­gic Research, Exxon­Mo­bil Research and Engi­neer­ing Com­pa­ny and is respon­si­ble for man­ag­ing emerg­ing-oppor­tu­ni­ty pro­grams that sup­port the Corporation’s gen­er­al inter­est.

2009 Spring Symposium

 
Jochen Lauter­bach
Depart­ment of Chem­i­cal Engi­neer­ing
Uni­ver­si­ty of Delaware
Newark, DE

Abstract — We have been using high-through­put (HT) approach­es based on rapid-scan FTIR hyper­spec­tral imag­ing in the mid-infrared to screen cat­a­lyst for­mu­la­tions for the dis­cov­ery and opti­miza­tion of new and improved mate­ri­als. In com­bi­na­tion with HT meth­ods, we also employ a vari­ety of more tra­di­tion­al spec­tro­scop­ic meth­ods to under­stand the under­ly­ing fun­da­men­tal sci­ence.

Two exam­ples will be used to illus­trate this research approach: de-NOx for auto­mo­tive exhaust after-treat­ment and ammo­nia decom­po­si­tion cat­a­lysts for CO free hydro­gen generation.While HT screen­ing is a macro­scop­ic analy­sis tech­nique, we are also inter­est­ed in observ­ing non-lin­ear phe­nom­e­na on work­ing cat­a­lysts in situ on the microscale using spec­tro­scop­ic imag­ing based on ellip­som­e­try. The col­lec­tive, glob­al behav­iour of a cat­alyt­ic sys­tem depends on the effec­tive com­mu­ni­ca­tion of local reac­tiv­i­ty vari­a­tions to dis­tant points in the sys­tem. One mode of com­mu­ni­ca­tion occurs via par­tial pres­sure fluc­tu­a­tions in the gas-phase above the cat­alyt­i­cal­ly active sur­face. This gas-phase cou­pling mode is con­sid­ered to be most effec­tive under vac­u­um con­di­tions, where the mean free path between mol­e­c­u­lar col­li­sions is large. We take advan­tage of a spa­tial­ly dis­trib­uted sys­tem of iso­lat­ed chem­i­cal oscil­la­tors to inves­ti­gate the details of gas-phase com­mu­ni­ca­tion in the 10–3 Torr range. Char­ac­ter­i­za­tion of local gas-phase vari­a­tions, in con­junc­tion with local kinet­ic activ­i­ty on the sur­face, shows that sur­face/­gas-phase inter­ac­tion might dif­fer from the con­ven­tion­al assump­tion of a gra­di­ent free, mol­e­c­u­lar flow envi­ron­ment near the sur­face. This analy­sis pro­vides a quan­ti­ta­tive esti­mate of the effec­tive gas-phase cou­pling length in a het­ero­ge­neous sys­tem. This cou­pling length was found to be in agree­ment with sur­face imag­ing results which qual­i­ta­tive­ly showed cou­pling between oscil­la­tors.

Speaker’s Biog­ra­phy — Jochen Lauter­bach received his Diplo­ma in Physics at the Uni­ver­si­ty of Bayreuth, Ger­many under Prof. J. Küp­pers and his Doc­tor­ate in Phys­i­cal Chem­istry at the Fritz-Haber Insti­tute of the Max-Planck-Soci­ety, Berlin, Ger­many under Pro­fes­sor G. Ertl. He came to the US in 1994 with a Feodor-Lynen-Fel­low­ship of the Alexan­der von Hum­boldt-Foun­da­tion and per­formed his post-doc­tor­al work at the Uni­ver­si­ty of Cal­i­for­nia at San­ta Bar­bara under Prof. W.H. Wein­berg. He joined the fac­ul­ty at Pur­due in 1996 and, in 2002, moved to the Uni­ver­si­ty of Delaware, where he cur­rent­ly is a Pro­fes­sor in the Chem­i­cal Engi­neer­ing Depart­ment. His research inter­ests include the design of cat­alyt­ic mate­ri­als using high-through­put screen­ing method­olo­gies and in situ spec­tro­scop­ic tech­niques, devel­op­ment of cat­a­lyst syn­the­sis method­olo­gies based on microemul­sions, nano-engi­neered poly­mer films from renew­able feed­stock, and non-lin­ear dynam­ics of chem­i­cal reac­tions, in par­tic­u­lar exter­nal spa­tiotem­po­ral forc­ing. Pro­fes­sor Lauter­bach has pub­lished close to 100 papers/book chap­ters and has giv­en over 150 invit­ed pre­sen­ta­tions.

2009 Spring Symposium

 
Gary Haller
Depart­ment of Chem­istry
Yale Uni­ver­si­ty
New Haven, CT

Abstract — Mobil com­po­si­tion of mate­r­i­al No. 41 (MCM-41) was dis­closed in 1992 and short­ly after a research project was ini­ti­at­ed at Yale to use these mate­ri­als to demon­strate a radius of cur­va­ture effect on cat­alyt­ic activ­i­ty. The “radius of cur­va­ture” effect implies a change in the sol­id sur­face ten­sion of the pore wall as the pore diam­e­ter (cur­va­ture) is changed that is expect­ed to change the activity/selectivity of an iso­lat­ed cat­alyt­ic site on the pore wall of the sup­port. An iso­lat­ed site can be formed by iso­mor­phous sub­sti­tu­tion (dur­ing syn­the­sis) of some Si cations by V cations in the MCM-41 sil­i­ca matrix. Sev­er­al labs have report­ed that iso­lat­ed V sites on a sil­i­ca sup­port are prefer­able to dimers, oligomers or poly­mers of van­dia on a sil­i­ca sup­port for the oxi­da­tion of methanol to formalde­hyde. MCM-41 might have an advan­tage rel­a­tive to oth­er sil­i­cas because of its very high sur­face area, >1000 m²/g. Both the air oxi­da­tion of methanol and methane to formalde­hyde have been used as probe reac­tions for cat­alyt­ic char­ac­ter­i­za­tion of V-MCM-41. SBA-15 has a sim­i­lar struc­ture to MCM-41, but larg­er pores and thick­er walls. Iso­mor­phous sub­sti­tu­tion of V dur­ing syn­the­sis is not prac­ti­cal, but well dis­persed V can be pre­pared post-syn­the­sis by graft­ing (reac­tion with sur­face hydrox­yls). The activ­i­ty for methanol oxi­da­tion on V-MCM-41 and V-SBA-15 will be com­pared and dis­cussed.

Speaker’s Biog­ra­phy — Gary L. Haller is the Hen­ry Pren­tiss Bec­ton Pro­fes­sor of Engi­neer­ing and Applied Sci­ence at Yale Uni­ver­si­ty with joint appoint­ments in the Depart­ments of Chem­i­cal Engi­neer­ing and Chem­istry. Pro­fes­sor Haller received a B.S. in math­e­mat­ics and chem­istry from the Uni­ver­si­ty of Nebras­ka at Kear­ney in 1962 and a Ph.D. in phys­i­cal chem­istry from North­west­ern Uni­ver­si­ty in 1966. Fol­low­ing a NATO Post-doc­tor­al Fel­low­ship at Oxford Uni­ver­si­ty, he joined the fac­ul­ty of Yale where he has held a vari­ety of admin­is­tra­tive posts that include Chair of the Depart­ment of Chem­i­cal Engi­neer­ing, Chair of the Coun­cil of Engi­neer­ing, and Deputy Provost for Phys­i­cal Sci­ences and Engi­neer­ing. He was Mas­ter of Jonathan Edwards Col­lege, one of twelve res­i­den­tial col­leges that com­prise Yale Col­lege 1997–2008.

Pro­fes­sor Haller’s research involved the mol­e­c­u­lar under­stand­ing of het­ero­ge­neous cat­a­lysts. His research com­bines the inor­gan­ic chem­istry of cat­a­lyst syn­the­sis, phys­i­cal chem­istry of spec­tro­scop­ic char­ac­ter­i­za­tion of het­ero­ge­neous cat­a­lysts, and the kinet­ics and mech­a­nism of sim­ple organ­ic reac­tions. Cur­rent research is focused on cat­a­lysts for the syn­the­sis of sin­gle walled car­bon nan­otubes and the appli­ca­tion of these car­bon nan­otubes as sup­ports for nov­el cat­alyt­ic reac­tions such as aque­ous phase reform­ing (a route to renew­able ener­gy sources).

2009 Spring Symposium

 
Danielle A. Hans­gen
Depart­ment of Chem­i­cal Engi­neer­ing
Uni­ver­si­ty of Delaware
Newark, DE

Abstract — The ammo­nia decom­po­si­tion reac­tion has recent­ly received increased atten­tion due to the pos­si­bil­i­ty of ammo­nia being used as a hydro­gen stor­age medi­um in a pos­si­ble hydro­gen econ­o­my. We have explored this decom­po­si­tion reac­tion through mul­ti­scale micro­ki­net­ic mod­el­ing for a num­ber of tran­si­tion met­al cat­a­lysts, includ­ing Cu, Pt, Ir, Ru, Pd, Rh, Co, Ni, Fe, W, and Mo, to bet­ter under­stand the reac­tion mech­a­nism. An under­stand­ing of the reac­tion mech­a­nism and elec­tron­ic prop­er­ties of these met­als has giv­en insight into how to tai­lor cat­a­lysts to improve cat­alyt­ic activ­i­ty for this reac­tion.

The mech­a­nism con­sists of 12 ele­men­tary reac­tion steps and 5 sur­face species, name­ly N, H, NH, NH₂, and NH₃. For many of the met­als, a large por­tion of the sur­face is cov­ered by adsor­bates. For these met­als, repul­sive adsor­bate-adsor­bate inter­ac­tions were expect­ed to change the bind­ing ener­gies of the sur­face species, there­by chang­ing the ele­men­tary reac­tion acti­va­tion bar­ri­ers and mod­i­fy­ing the cat­alyt­ic activ­i­ty [1]. Cov­er­age depen­dant atom­ic heats of chemisorp­tion were cal­cu­lat­ed through DFT using the Vien­na Ab-ini­tio Sim­u­la­tion Pack­age (VASP) for the var­i­ous tran­si­tion met­al cat­a­lysts. Cov­er­age depen­dant mol­e­c­u­lar bind­ing ener­gies were cal­cu­lat­ed using a method based on scal­ing rela­tion­ships pub­lished by Abild-Ped­er­son et al. [2] and acti­va­tion bar­ri­ers were cal­cu­lat­ed through the bond-order con­ser­va­tion (BOC) method [3].

Inclu­sion of the inter­ac­tion para­me­ters to the mod­els result­ed in reduced nitro­gen cov­er­ages and a peak shift in the vol­cano curve. The con­ver­sions were plot­ted against the char­ac­ter­is­tic nitro­gen heat of chemisorp­tion for each met­al, which was found to be an ade­quate descrip­tor for this reac­tion. The vol­cano curve of the con­ver­sions cal­cu­lat­ed through the micro­ki­net­ic mod­els are in good agree­ment with exper­i­men­tal data of sin­gle met­al cat­a­lysts by Gan­ley and cowork­ers [4]. The max­i­mum activ­i­ty was found at a nitro­gen heat of chemisorp­tion of approx­i­mate­ly 130 kcal/mol.

A DFT study of nitro­gen bind­ing ener­gies on Pt-3d bimetal­lic sur­faces showed a bind­ing ener­gy of 131 kcal/mol on the Ni-Pt-Pt sur­face, indi­cat­ing that it could be a poten­tial­ly active cat­a­lyst; there­fore sur­face sci­ence exper­i­ments were per­formed to assess the micro­ki­net­ic mod­el and DFT results. The Ni-Pt-Pt sur­face was found to be more active at decom­pos­ing ammo­nia at low tem­per­a­tures and des­orbed nitro­gen at low­er tem­per­a­tures than a Ru(0001) sur­face [5], cur­rent­ly the most active sin­gle met­al cat­a­lyst

Speaker’s Biog­ra­phy — Danielle Hans­gen received her Bachelor’s degree in chem­i­cal engi­neer­ing in 2005 from the Uni­ver­si­ty of Wash­ing­ton. She is cur­rent­ly a third year, PhD can­di­date in chem­i­cal engi­neer­ing at the Uni­ver­si­ty of Delaware. She is advised by Dr. Dion G. Vla­chos and Dr. Jing­guang G. Chen and is work­ing on the ratio­nal design of cat­a­lysts for the ammo­nia decom­po­si­tion reac­tion.

2009 Spring Symposium

 
Dr Christo­pher J. Kiely
Cen­ter for Advanced Mate­ri­als and Nan­otech­nol­o­gy
Lehigh Uni­ver­si­ty
Beth­le­hem, PA

Abstract — Sup­port­ed gold clus­ters and gold-pal­la­di­um nanopar­ti­cles are intense­ly stud­ied mate­ri­als pri­mar­i­ly because of their excit­ing poten­tial appli­ca­tions in catal­y­sis. The recent avail­abil­i­ty of aber­ra­tion cor­rect­ed ana­lyt­i­cal elec­tron micro­scopes is rev­o­lu­tion­iz­ing our abil­i­ty to char­ac­ter­ize the mor­phol­o­gy, crys­tal­log­ra­phy and chem­i­cal com­po­si­tion of such nanoscop­ic vol­umes of mate­ri­als and for the first time are giv­ing us more real­is­tic views of these cat­a­lyst sys­tems. To illus­trate the supe­ri­or imag­ing per­for­mance of this new gen­er­a­tion of elec­tron micro­scopes, we will present a high angle annu­lar dark field (HAADF) imag­ing study of a sys­tem­at­ic set of gold on iron oxide CO oxi­da­tion cat­a­lysts, rang­ing from those with lit­tle or no activ­i­ty, to oth­ers with very high activ­i­ties. Using this approach, com­bined with XPS analy­sis, we will unam­bigu­ous­ly demon­strate that the high cat­alyt­ic activ­i­ty for CO oxi­da­tion derives from the pres­ence of bi-lay­er clus­ters which are ~0.5 nm in diam­e­ter. We will also demon­strate that core-shell struc­tures in sub-5nm Au+Pd, Pd@Au and Au@Pd bimetal­lic nanopar­ti­cles can be direct­ly visu­al­ized using the z-con­trast sen­si­tiv­i­ty of the HAADF imag­ing tech­nique. To illus­trate the chem­i­cal analy­sis capa­bil­i­ties of aber­ra­tion cor­rect­ed ana­lyt­i­cal micro­scopes, we will describe the poten­tial advan­tages of com­bin­ing X-ray Ener­gy Dis­per­sive Spec­troscopy (XEDS) spec­trum imag­ing with mul­ti­vari­ate sta­tis­ti­cal analy­sis (MSA) tech­niques. Through sev­er­al case stud­ies of the Au-Pd bimetal­lic cat­a­lyst sys­tems, we will demon­strate that STEM-XEDS can pro­vide invalu­able high spa­tial res­o­lu­tion com­po­si­tion­al infor­ma­tion on (i) alloy homo­gene­ity and phase seg­re­ga­tion effects with­in indi­vid­ual nanopar­ti­cles, (ii) par­ti­cle size — alloy com­po­si­tion cor­re­la­tions, and (iii) alloy com­po­si­tion changes that can occur as these cat­a­lysts are used.

Speaker’s Biog­ra­phy — Chris Kiely obtained his BSc in Chem­i­cal Physics (1983) and PhD in Microstruc­tur­al Physics (1986) from Bris­tol Uni­ver­si­ty. From 1986–89 he was a vis­it­ing post­doc­tor­al research asso­ciate in the Mate­ri­als Research Lab­o­ra­to­ry at the Uni­ver­si­ty of Illi­nois at Urbana-Cham­paign. He joined the Mate­ri­als Sci­ence and Engi­neer­ing Depart­ment at Liv­er­pool Uni­ver­si­ty as a Lec­tur­er in 1989, where he worked his way through the ranks until even­tu­al­ly being award­ed a Per­son­al Chair in Mate­ri­als Chem­istry in 1999. Kiely joined Lehigh Uni­ver­si­ty (Penn­syl­va­nia, USA) as Pro­fes­sor of Mate­ri­als Sci­ence and Engi­neer­ing in 2002. He is cur­rent­ly the Direc­tor of the Cen­ter of the Nanochar­ac­ter­i­za­tion Lab­o­ra­to­ry at Lehigh Uni­ver­si­ty, which hous­es an array of twelve elec­tron micro­scopes, includ­ing two aber­ra­tion cor­rect­ed instru­ments. He also serves as the Direc­tor of the Lehigh Microscopy Schools. His research exper­tise lies in the appli­ca­tion and devel­op­ment of trans­mis­sion elec­tron microscopy tech­niques for the study of nanoscale fea­tures in mate­ri­als. His areas of inter­est include cat­a­lyst mate­ri­als, nanopar­ti­cle self-assem­bly, car­bona­ceous mate­ri­als, and het­eroepi­tax­i­al inter­face struc­tures. He is also involved in microscopy tech­nique devel­op­ment, and his cur­rent inter­ests include X-Ray Ultra­mi­croscopy (XuM) and aber­ra­tion cor­rect­ed Ana­lyt­i­cal Elec­tron Microscopy (AEM).