May Molecule of the Month
May 2023’s Molecule of the Month is cobalt(II) phthalocyanine (CoPc)! In the latest report of light-driven CO₂ reduction with this catalyst, CoPc was noncovalently immobilized on cadmium sulfide (CdS)-dispersed carbon nanotubes (CNTs). The CdS light absorbers generated electron-hole pairs, and the electrons were rapidly transferred from the CdS through the CNTs to the CoPcs for selective CO₂-to-CO conversion. These proposals were supported by ultrafast transient absorption (TA) measurements of CdS exciton bleaching. Moreover, systems without the CoPc or CdS did not demonstrate CO formation, and a CdS/CoPc system was both much slower and much more biased towards H₂ formation than the fully constituted ternary hybrid catalyst. Additionally, the CNT created local photothermal heating for the conversion of amine-captured CO₂ to CO without other energy inputs. In situ Raman spectra during CO₂RR revealed that CoPc was observed during light-driven CO formation, implicating it as the active species. In situ UV-Visible spectroscopic studies showed doubly-reduced catalyst CoPc reacted almost immediately with CO₂ to generate singly-reduced CoPc, consistent with complementary Raman experiments. The CHASE collaboration was lead by Hailiang Wang’s group with spectroscopic measurements from Tim Lian’s laboratory and additional contributions from Judy Cha’s group.
Check it out at https://doi.org/10.1002/anie.202302152 !
April Molecule of the Month
April 2023’s Molecule of the Month is N-trans [Ru(terpy-4’-(C₆H₄-4-(C(O)NHC₃H₆-3-silatrane)))(Mebim-py)(NCCH₃)](PF₆)₂! This ruthenium silatrane catalyst was attached to tantalum(V) nitride (Ta₃N₅), which is a potential photoanode for water oxidation applications, and was shown to passivate defects on the surface. The spatial and energetic distribution of trap states throughout Ta₃N₅ thin films with and without the immobilized Ru silatrane catalyst was characterized using drive-level capacitance profiling (DLCP). The Ru silatrane-immobilized Ta₃N₅ was shown to have over two orders of magnitude lower density of surface defects as compared to the Ru silatrane-free Ta₃N₅. The Ru silatrane molecule’s surface passivation led to suppressed trapping and recombination of photoexcited carriers, which was characterized by absorption, photoluminescence, and transient photovoltage measurements. The findings from this study may guide the integration and development of high-performance Ta₃N₅ thin film devices. The CHASE collaboration was lead by the Lopez group with synthetic efforts by CHASE staff scientist Dr. Stephen J. Tereniak.
Check it out at https://doi.org/10.1021/acsami.2c19275!
March Molecule of the Month
Image and post credit: Dr. Steve Tereniak
March 2023’s Molecule of the Month is fac-Re(4,4’-bis(4-butylsilatrane)-2,2’-bipyridine)(CO)₃Cl! This Re-silatrane CO₂ reduction catalyst was attached to TiO₂-coated, n-type silicon(100) and shown to give a Faradaic efficiency of about 30% for the reduction of CO₂ to CO, whereas an amide-linked Re silatrane catalyst silicon electrode gave only 3% Faradaic efficiency for this reduction. The CO₂ reduction performance correlates with the solution electrochemistry of these complexes in that compounds without amides gave well-behaved reductions, whereas a compound with an amide gave poor reductive electrochemical features. A similar Re-bpy CO₂ reduction catalyst with only one alkylsilatrane functional group was attached to TiO₂-coated, low-doped p-type silicon(100) and was shown to give a photovoltage of ~0.5 V under illumination. Characterization techniques used in the study include X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR), and cyclic voltammetry (CV). The CHASE collaboration was lead by the Hazari, Mayer, and Concepcion groups and also included contributions by the Cahoon, Lockett, Meyer, and Wang groups as well as CHASE staff scientists Dr. Carrie L. Donley and Dr. Renato N. Sampaio.
Check it out at https://doi.org/10.1021/acs.inorgchem.2c04137!
February Molecule of the Month
Image and post credit: Dr. Steve Tereniak
February 2023’s Molecule of the Month is fac-Re(5-(p-styrene)-phen)(CO)₃Cl!
This CO₂ reduction catalyst was attached to hydrogen-terminated silicon(111) by sonochemical hydrosilylation, the first example of sonochemical hydrosilylation applied to immobilize an organometallic complex on a Si photoelectrode, and backfilled with 1-hexene! The hybrid photoelectrode was characterized by a variety of techniques including attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-IR), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM), and contact angle goniometry. The paper was a collaboration among the Dempsey, Castellano, Atkin, Fakhraai, and Meyer groups with photoelectron spectroscopy by CHASE staff scientist Dr. Carrie L. Donley.
Check it out at https://pubs.acs.org/doi/10.1021/acsami.2c17078!