Excessive carbon dioxide (CO2) emissions by combustions of fossil fuels is linked to the global warming and rapid climate change. One promising route to lowering the concentration of CO2 in the atmosphere is to reduce it to useful small molecules via photoelectrocatalytic hydrogenation, which would enable solar energy storage with a zero carbon emission cycle and perform a more efficient separation of the photogenerated electron and hole pair than pure photocatalysis. Indeed, photoelectrocatalytic CO2 reduction has been an intense focus of research. Using density functional theory (DFT), we studied CO2 reduction reaction on the defective anatase TiO2 (101) surface, at both the solvent/catalyst and the electrolyte/catalyst interfaces. The analysis of the electronic structure of the surface shows a contrast between the solvent/catalyst and the electrolyte/catalyst interfaces, which results in the two corresponding catalytic cycles being distinct. Our study explains at the electronic and mechanistic level why methanol is the main product in the presence of the electrolyte and the overpotential not only controlled by reaction process but also the diffusion process.

High-level electronic structure calculations of the low-lying energy electronic states for ThH, ThH–, and ThH+ are reported and compared to experimental measurements. The inclusion of spin–orbit coupling is critical to predict the ground-state ordering as inclusion of spin–orbit switches the coupled-cluster CCSD­(T) ordering of the two lowest energy states for ThH and ThH+. At the multireference spin–orbit SO-CASPT2 level, the ground states of ThH, ThH–, and ThH+ are predicted to be the 2Δ3/2, 3Φ2, and 3Δ1 states, respectively. The adiabatic electron affinity is calculated to be 0.820 eV, and the vertical detachment energy is calculated to be 0.832 eV in comparison to an experimental value of 0.87 ± 0.02 eV. The observed ThH– photoelectron spectrum has many transitions, which approximately correlate with excitations of Th+ and/or Th. The adiabatic ionization energy of ThH including spin–orbit corrections is calculated to be 6.181 eV. The natural bond orbital results are consistent with a significant contribution of the Th+H– ionic configuration to the bonding in ThH. The bond dissociation energies for ThH, ThH–, and ThH+ using the Feller–Peterson–Dixon approach were calculated to be similar for all three molecules and lie between 259 and 280 kJ/mol.

Recent advances in microdroplet chemistry have shown that chemical reactions in water microdroplets can be accelerated by several orders of magnitude compared to the same reactions in bulk water. Among the large plethora of unique properties of microdroplets, an especially intriguing one is the strong reducing power that can be sometimes as high as alkali metals as a result of the spontaneously generated electrons. In this study, we design a catalyst-free strategy that takes advantage of the reducing ability of water microdroplets to reduce a certain molecule, and the reduced form of that molecule can convert CO 2 into value-added products. By spraying the water solution of C 6 F 5 I into microdroplets, an exotic and fragile radical anion, C 6 F 5 I •− , is observed, where the excess electron counter-intuitively locates on the σ* antibonding orbital of the C−I bond as evidenced by anion photoelectron spectroscopy. This electron weakens the C−I bond and causes the formation of C 6 F 5 − , and the latter attacks the carbon atom on CO 2 , forming the pentafluorobenzoate product, C 6 F 5 CO 2 − . This study provides a good example of strategically making use of the spontaneous properties of water microdroplets, and we anticipate that microdroplet chemistry will be a green avenue rich in new opportunities in CO 2 utilization.

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The results of a combined experimental and computational study of the uranium atom are presented with the aim of determining its electron affinity. Experimentally, the electron affinity of uranium was measured via negative ion photoelectron spectroscopy of the uranium atomic anion, U−. Computationally, the electron affinities of both thorium and uranium were calculated by conducting relativistic coupled-cluster and multi-reference configuration interaction calculations. The experimentally determined value of the electron affinity of the uranium atom was determined to be 0.309 ± 0.025 eV. The computationally predicted electron affinity of uranium based on composite coupled cluster calculations and full four-component spin–orbit coupling was found to be 0.232 eV. Predominately due to a better convergence of the coupled cluster sequence for Th and Th−, the final calculated electron affinity of Th, 0.565 eV, was in much better agreement with the accurate experimental value of 0.608 eV. In both cases, the ground state of the anion corresponds to electron attachment to the 6d orbital.