Surface modification of (semi)conducting materials with polymers provides a strategy for interfacing electrodes with electrocatalysts for reactions of industrial importance. The resulting constructs create opportunities to capture, convert and store solar energy in the form of chemical bonds, generating solar fuels. This thesis describes III-V semiconductors, modified with molecular catalysts embedded in thin-film polymeric coatings. Overarching goals of this work include building protein-like, soft-material environments on solid-state electrode surfaces. This approach enables coordination of earth-abundant metal centers within the three-dimensional molecular coatings to modulate the electronic and catalytic properties of the overall assembly and provide assemblies for studying the effects of polymeric-encapsulation on electrocatalytic as well as photoelectrosynthetic performance. In summary, this work provides 1) new approaches to designing, interfacing, and characterizing (semi)conducting and catalytic materials to effectively power chemical transformations (including hydrogen evolution and carbon dioxide reduction), and 2) kinetic models for better understanding the structure-function relationships governing the performance of these assemblies.

As the simplest carboxylic acid, formic acid (FA) is ubiquitous to Earth’s atmosphere, helping seed cloud nucleation and leading to acid rain. By studying the interactions between FA and high intensity light under high vacuum, conditions similar to the upper atmosphere, on other planets (either in the solar system or beyond), and even in interstellar media are emulated. These results were produced from a home built vacuum chamber system, with a Wiley-McLaren time of flight mass spectrometer and using femtosecond (fs) laser pulses. The laser characteristics were as follows: a pulse width >35 fs, center wavelength of 400 nm (probe pulse was 800 nm for the pump-probe investigation), and laser intensities at ~10¹⁵ W/cm².At high laser intensities, the first direct experimental evidence of CO³⁺ was recorded from the Coulomb explosion (CE) of the formic acid dimer (FAD) from a molecular beam. Theoretical calculations provided further evidence for the formation of CO³⁺ from the vertical ionization of FAD. When (FA)_n(H₂O)_mH⁺ clusters (n = 1-7 and m = 0-1) were exposed to similar laser intensities, the larger clusters (n = 5-7) favored complete atomization from CE, indicating that the repulsive forces within the clusters at those sizes was too great to withstand to form CO³⁺. The protonated nature of the clusters and the peak shapes recorded in the mass spectra suggested that neutral (FA)_n⁺ clusters undergo a dissociation mechanism within the extraction region. A novel technique was created to calculate these dissociation times on the order of 100s of nanoseconds (ns), increasing by ~10 ns for each additional FA molecule. Using pump-probe spectroscopy, it was observed similarly that neutral (FA)_n clusters with n > 1, showed evidence of ion pair formation of the form [(FA)_nH⁺·OOCH^-] on the sub-picosecond timescale, increasing by 70 fs per FA molecule. Both trends indicate that the neutral clusters prefer to form compact 3d structures, but after photoexcitation the clusters have competing pathways to ionization, either through multiphoton ionization (ns dynamics) or ion pair formation (fs dynamics) that inevitably lead to the expansion and subsequent rearrangement into linear chains for the protonated cluster.

Microsolvation studies have begun to shed the light on the impact that single water molecules have on the structure of a molecule. The difference in behavior that molecules show when exposed to an increasing number of water molecules has been considered important but remains elusive. The cluster distributions of formic acid were studied for its known importance as an intermediate in the water gas shift reaction. Implementations of the water gas shift reaction range from a wide range of applications. Studies have proposed implementations such as variety such as making water on the manned mission to mars and as an industrial energy source. The reaction pathway of formic acid favors decarboxylation in solvated conditions but control over the pathway is an important field of study. Formic acid was introduced into a high vacuum system in the form of a cluster beam via supersonic expansion and was ionized with the second harmonic (400nm) of a pump-probe laser. Mass spectra showed a ‘magic’ 5,1 (formic acid, water) peak which showed higher intensity than was usually observed in clusters with 1 water molecule. Peak integration showed a higher relative abundance for the 5,1 cluster as well and showed the increased binding favorability of this conformation. As a result, there is an enhanced probability of molecules sticking together in this arrangement and this is due to the stable, cage-like structure that the formic acid forms when surrounding the water molecule.

One strategic objective of the National Aeronautics and Space Administration (NASA) is to find life on distant worlds. Current and future missions either space telescopes or Earth-based observatories are frequently used to collect information through the detection of photons from exoplanet atmospheres. The primary challenge is to fully understand the nature of these exo-atmospheres. To this end, atmospheric modeling and sophisticated data analysis techniques are playing a key role in understanding the emission and transmission spectra of exoplanet atmospheres. Of critical importance to the interpretation of such data are the opacities (or absorption cross-sections) of key molecules and atoms. During my Doctor of Philosophy years, the central focus of my projects was assessing and leveraging these opacity data. I executed this task with three separate projects: 1) laboratory spectroscopic measurement of the infrared spectra of CH4 in H2 perturbing gas in order to extract pressure-broadening and pressure-shifts that are required to accurately model the chemical composition of exoplanet atmospheres; 2) computing the H2O opacity data using ab initio line list for pressure and temperature ranges of 10^-6–300 bar and 400–1500 K, and then utilizing these H2O data in radiative transfer models to generate transmission and emission exoplanetary spectra; and 3) assessing the impact of line positions in different H2O opacities on the interpretation of ground-based observational exoplanetary data through the cross-correlation technique.