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This work is focused on evaluating the performance of exchange-correlation functionals from density functional theory in providing descriptor values derived from the electron density of saddle point structures (transition states) in chemical reactions. The properties investigated were obtained from the quantum theory of atoms in molecules, including atomic charges and electron density topological data at the bond critical points. In addition, parameters from the Interacting quantum atom energy partition were used as well in this comparative study. The reference values are attained in coupled cluster calculations with iterative single and double excitations (CCSD). Six elementary reactions are considered here: CO + H

The development of visible-light active photocatalysts is vital to harvest the solar irradiation and build efficient photoelectrochemical devices. Bismuth oxyhalide (BiOCl, BiOBr and BiOI) materials stand out due to their remarkable properties, e.g., the band gap energy can be tuned from 1.9 to 3.4 eV depends on the halide employed. However, the hydrothermal synthesis of this material class was not properly investigated and compared. Then, we evaluated the effect of the hydrothermal treatment in the BiOX’s structural, electronic, morphological and textural properties and the relationship with their photocatalytic performance. Methylene blue (MB) dye was used as probe for photocatalytic performance evaluation under ultraviolet (UV) and visible (Vis) radiation. BiOCl and BiOBr samples showed a good photoactivity under both UV and visible radiation, on other hand the BiOI samples was not active, likely due to the fast charge recombination. BiOCl and BiOBr samples exhibit a favorably interaction with MB dye, because their surfaces are negatively charged. BiOCl samples were able to promote around 40 and 80% of the MB dye degradation under visible and UV radiation, respectively. The samples were also employed as photoanode for O2 evolution, BiOI sample exhibited the best performance, due to the synergistic effect of photocatalysis and electrocatalysis.