TY - JOUR
T1 - Adsorption of Formic Acid on CH3NH3PbI3 Lead-Halide Organic-Inorganic Perovskites
AU - Nayakasinghe, M. T.
AU - Han, Yulun
AU - Sivapragasam, N.
AU - Kilin, Dmitri S.
AU - Oncel, N.
AU - Burghaus, U.
N1 - Publisher Copyright:
© 2019 American Chemical Society.
PY - 2019/9/19
Y1 - 2019/9/19
N2 - The adsorption kinetics of formic acid (HCOOH) was studied under ultrahigh vacuum (UHV) on lead-halide organic-inorganic perovskites (CH3NH3PbI3) supported on indium-doped tin oxide (ITO). The thin film samples were made at ambient pressure using the common liquid-phase synthesis, but samples were degassed under UHV. We studied real-world samples which do have some carbon impurities. Adsorption and decomposition kinetics were characterized with thermal desorption spectroscopy. Furthermore, samples' composition (including impurities) were inspected under UHV with Auger electron spectroscopy and X-ray photoelectron spectroscopy. Accordingly, formic acid adsorbs molecularly at 100 K but decomposed above 600 K. On ITO or thermally decomposed perovskite samples, formic acid adsorbs only molecularly. The gas-phase species detected are consistent with a decomposition mechanism via the formation of formate (HCOO) and formyl (HCO) intermediates. The perovskite itself also decomposed thermally, but it is stabilized to some extent by the adsorbed formic acid. In addition, density functional theory calculations (DFT) were used to characterize the molecular adsorption pathway of HCOOH as well as the adsorption of various decomposition fragments. Accordingly, molecular formic acid adsorption is facilitated by a Pb-O bond formation between a 5-fold coordinated Pb atom on the surface of the perovskite and the carbonyl O atom of formic acid.
AB - The adsorption kinetics of formic acid (HCOOH) was studied under ultrahigh vacuum (UHV) on lead-halide organic-inorganic perovskites (CH3NH3PbI3) supported on indium-doped tin oxide (ITO). The thin film samples were made at ambient pressure using the common liquid-phase synthesis, but samples were degassed under UHV. We studied real-world samples which do have some carbon impurities. Adsorption and decomposition kinetics were characterized with thermal desorption spectroscopy. Furthermore, samples' composition (including impurities) were inspected under UHV with Auger electron spectroscopy and X-ray photoelectron spectroscopy. Accordingly, formic acid adsorbs molecularly at 100 K but decomposed above 600 K. On ITO or thermally decomposed perovskite samples, formic acid adsorbs only molecularly. The gas-phase species detected are consistent with a decomposition mechanism via the formation of formate (HCOO) and formyl (HCO) intermediates. The perovskite itself also decomposed thermally, but it is stabilized to some extent by the adsorbed formic acid. In addition, density functional theory calculations (DFT) were used to characterize the molecular adsorption pathway of HCOOH as well as the adsorption of various decomposition fragments. Accordingly, molecular formic acid adsorption is facilitated by a Pb-O bond formation between a 5-fold coordinated Pb atom on the surface of the perovskite and the carbonyl O atom of formic acid.
UR - https://www.scopus.com/pages/publications/85072635039
U2 - 10.1021/acs.jpcc.9b03319
DO - 10.1021/acs.jpcc.9b03319
M3 - Article
AN - SCOPUS:85072635039
SN - 1932-7447
VL - 123
SP - 22873
EP - 22886
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 37
ER -