skip to content

Department of Chemistry

 

David M. Halat

Research

Traditional solid oxide fuel cells (SOFCs) operate at or above 800°C. An outstanding problem in current SOFC research is enabling electrochemical functionality at 'intermediate' temperatures (400-800°C). Mixed ionic-electronic conductors (MIECs) are of significant interest as cathode materials for the next generation of SOFCs as their large oxide ion conductivity helps overcome sluggish oxygen reduction kinetics at the cathode at these lower temperatures.

Our group has previously shown solid-state nuclear magnetic resonance (ssNMR) can resolve both local structure and dynamics in SOFC electrolytes to gain insight into fundamental mechanisms of ionic conductivity and ultimately enable the selection of improved materials. A similar approach to study MIECs is complicated by the presence of paramagnetic transition metal (TM) cations (e.g. Ni2/3+, Mn3+). Though TM ions critically provide electronic conductivity in an operational SOFC cathode, their paramagnetism severely broadens resonances from adjacently bonded nuclei as observed by NMR.

In my work, both experimental (ssNMR) and computational (periodic DFT) techniques converge to help assign NMR spectra of MIECs on the basis of paramagnetic interactions. As a model MIEC, we have focused on the perovskite-derived Ruddlesden-Popper material La2NiO4+δ, which shows remarkably high oxygen conductivity at intermediate temperatures. Through variable-temperature NMR, we resolve two distinct mechanisms of O2- movement via interstitial and vacancy migration. These are among the first ssNMR studies of oxide ion dynamics in paramagnetic materials.


Hot spectra: 17O MAS VT-NMR spectra of La2NiO4+δ at operational SOFC temperatures (600-800°C) provide evidence for two different mechanisms of oxygen exchange.

I was previously in the group of Rob Walker at Montana State University, studying mechanisms of SOFC anode operation and degradation through in situ high-temperature vibrational Raman spectroscopy (see publications). I also briefly did similar work at the Energy Futures Lab (Fuel Cell Network) at Imperial College London, UK.

Education
2013-2018 
University of Cambridge
Cambridge, UK
Ph.D. Chemistry (with Clare Grey FRS) 

2009-2013 
Montana State University
Bozeman, MT
B.S. Chemistry
B.S. Mathematics

Publications

13.  Wu, Y.; Halat, D. M.; Wei, F.; Binford, T.; Seymour, I. D.; Gaultois, M. W.; Shaker, S.; Wang, J.; Grey, C. P.; Cheetham, A. K. Mixed X-site formate-hypophosphite hybrid perovskites. Chem. Eur. J., 24, 11309–11313 (2018).

12.  Halat, D. M.; Dunstan, M. T.; Gaultois, M. W.; Grey, C. P.  Study of defect chemistry in the system La2-xSrxNiO4+δ by 17O solid-state NMR spectroscopy and Ni K-edge XANES. Chem. Mater. 30, 4556–4570 (2018).

11.  Lebens-Higgins, Z. W.; Sallis, S.; Faenza, N. V.; Badway, F.; Pereira, N.; Halat, D. M.; Wahila, M.; Schlueter, C.; Lee, T.-L.; Yang, W.; Grey, C. P.; Amatucci, G. G.; Piper, L. F. J. Evolution of the Electrode–Electrolyte Interface of LiNi0.8Co0.15Al0.05O2 Electrodes Due to Electrochemical and Thermal Stress. Chem. Mater., 30, 958–969 (2018).

10.  Kim, G.; Griffin, J. M.; Blanc, F.; Halat, D. M.; Haile, S. M.; Grey, C. P. Revealing Local Dynamics of the Protonic Conductor CsH(PO3H) by Solid-State NMR Spectroscopy and First-Principles Calculations. J. Phys. Chem. C, 121, 27830–27838 (2017).

9.  Hope, M. A.; Halat, D. M.; Magusin, P. C. M. M.; Paul, S.; Peng, L.; Grey, C. P. Surface-selective direct 17O DNP NMR of CeO2 nanoparticles. Chem. Commun. 53, 2142–2145 (2017).

8. Pecher, O.*; Halat, D. M.*; Lee, J.; Liu, Z.; Griffith, K. J.; Braun, M.; Grey, C. P. Enhanced efficiency of solid-state NMR investigations of energy materials using an external automatic tuning/matching (eATM) robot. J. Magn. Reson. 275, 127–136 (2017). (* = equal contribution)

7.  Halat, D. M.; Dervişoğlu, R.; Kim, G.; Dunstan, M. T.; Blanc, F.; Middlemiss, D. S.; Grey, C. P. Probing Oxide-Ion Mobility in the Mixed Ionic–Electronic Conductor La2NiO4+δ  by Solid-State 17O MAS NMR Spectroscopy.  J. Am. Chem. Soc. 138, 11958–11969 (2016).

6. Seymour, I. D.; Middlemiss, D. S.; Halat, D. M.; Trease, N. M.; Pell, A. J.; Grey, C. P. Characterizing Oxygen Local Environments in Paramagnetic Battery Materials via 17O NMR and DFT Calculations. J. Am. Chem. Soc. 138, 9405–9408 (2016).

5. Reeping, K. W.; Halat, D. M.; Kirtley, J. D.; McIntyre, M. D.; Walker, R. A. In Situ Optical and Electrochemical Studies of SOFC Carbon Tolerance. ECS Trans. 61, 57–63 (2014).

4. McIntyre, M. D.; Kirtley, J. D.; Halat, D. M.; Reeping, K. W.; Walker, R. A. In Situ Spectroscopic Studies of Carbon Formation in SOFCs Operating with Syn-gas. ECS Trans. 57, 1267–1275 (2013).

3. Kirtley, J. D.; McIntyre, M. D.; Halat, D. M.; Walker, R. A. Insights into SOFC Ni/YSZ Anode Degradation Using In-Situ Spectrochronopotentiometry. ECS Trans. 50, 3–15 (2013). 

2. Kirtley, J.; Singh, A.; Halat, D.; Oswell, T.; Hill, J. M.; Walker, R. A. In Situ Raman Studies of Carbon Removal from High Temperature Ni–YSZ Cermet Anodes by Gas Phase Reforming Agents. J. Phys. Chem. C 117, 25908–25916 (2013).

1. Kirtley, J. D.; Halat, D. M.; McIntyre, M. D.; Eigenbrodt, B. C.; Walker, R. A. High-Temperature ‘Spectrochronopotentiometry’: Correlating Electrochemical Performance with In Situ Raman Spectroscopy in Solid Oxide Fuel Cells.  Anal. Chem. 84, 9745–9753 (2012).

Contact
Dr David Halat
Email: dh471@cam.ac.uk 
Office: +44(0)1223 336484 

Address:
 Department of Chemistry
 University of Cambridge
 Lensfield Road
 Cambridge, CB2 1EW
 United Kingdom

Publications

Mixed X-Site Formate-Hypophosphite Hybrid Perovskites
Y Wu, DM Halat, F Wei, T Binford, ID Seymour, MW Gaultois, S Shaker, J Wang, CP Grey, AK Cheetham
– Chemistry
(2018)
24,
11309
Study of Defect Chemistry in the System La2-xSrxNiO4+delta by O-17 Solid-State NMR Spectroscopy and Ni K-Edge XANES
DM Halat, MT Dunstan, MW Gaultois, S Britto, CP Grey
– Chemistry of Materials
(2018)
30,
4556
Evolution of the Electrode-Electrolyte Interface of LiNi0.8Co0.15Al0.05O2 Electrodes Due to Electrochemical and Thermal Stress
ZW Lebens-Higgins, S Sallis, NV Faenza, F Badway, N Pereira, DM Halat, M Wahila, C Schlueter, TL Lee, W Yang, CP Grey, GG Amatucci, LFJ Piper
– Chemistry of Materials
(2018)
30,
958
Revealing Local Dynamics of the Protonic Conductor CsH(PO 3 H) by Solid-State NMR Spectroscopy and First-Principles Calculations
G Kim, JM Griffin, F Blanc, DM Halat, SM Haile, CP Grey
– Journal of Physical Chemistry C
(2017)
121,
27830
Enhanced efficiency of solid-state NMR investigations of energy materials using an external automatic tuning/matching (eATM) robot
O Pecher, DM Halat, J Lee, Z Liu, KJ Griffith, M Braun, CP Grey
– Journal of Magnetic Resonance
(2017)
275,
127
Surface-selective direct 17 O DNP NMR of CeO 2 nanoparticles
MA Hope, DM Halat, PCMM Magusin, S Paul, L Peng, CP Grey
– Chemical communications (Cambridge, England)
(2017)
53,
2142
Probing Oxide-Ion Mobility in the Mixed Ionic-Electronic Conductor La<inf>2</inf>NiO<inf>4+δ</inf>by Solid-State<sup>17</sup>O MAS NMR Spectroscopy
DM Halat, R Dervişoğlu, G Kim, MT Dunstan, F Blanc, DS Middlemiss, CP Grey
– Journal of the American Chemical Society
(2016)
138,
11958
Characterizing Oxygen Local Environments in Paramagnetic Battery Materials via O-17 NMR and DFT Calculations
ID Seymour, DS Middlemiss, DM Halat, NM Trease, AJ Pell, CP Grey
– Journal of the American Chemical Society
(2016)
138,
9405

Research Group

Telephone number

01223 336484

Email address

dh471@cam.ac.uk