TiO2 anatase plays a central role in energy and environmental research. A major bottleneck toward developing artificial photosynthesis with TiO2 is that it only absorbs ultraviolet light, owing to its large bandgap of 3.2 eV. If one could reduce the bandgap of anatase to the visible region, TiO2-based photocatalysis could become a competitive clean energy source. Here, using scanning tunneling microscopy and spectroscopy in conjunction with density functional theory calculations, we report the discovery of a highly reactive titanium-terminated anatase surface with a reduced bandgap of less than 2 eV, stretching into the red portion of the solar spectrum. By tuning the surface preparation conditions, we can reversibly switch between the standard anatase surface and the newly discovered low bandgap surface phase. The identification of a TiO2 anatase surface phase with a bandgap in the visible and high chemical reactivity has important implications for solar energy conversion, photocatalysis, and artificial photosynthesis.

The prevalence of PTSD is higher in drug than in alcohol dependence. The more strictly PTSD is diagnosed (by interviewer and questionnaire) the more clearly are associations with characteristics of SUD. PTSD seems to be an independent risk factor for an unfavorable outcome of SUD.

Nickel (oxy)hydroxide-based (NiOH) materials are widely used for energy storage and conversion devices. Understanding dynamic processes at the solid-liquid interface of nickel (oxy)hydroxide is important to improve reaction kinetics and efficiencies. In this study, in situ electrochemical atomic force microscopy (EC-AFM) was used to directly investigate dynamic changes of single-layered Ni(OH) nanosheets during electrochemistry measurements. Reconstruction of Ni(OH) nanosheets, along with insertion of ions from the electrolyte, results in an increase of the volume by 56% and redox capacity by 300%. We also directly observe Fe cations adsorb and integrate heterogeneously into or onto the nanosheets as a function of applied potential, further increasing apparent volume. Our findings are important for the fundamental understanding of NiOH-based supercapacitors and oxygen-evolution catalysts, illustrating the dynamic nature of Ni-based nanostructures under electrochemical conditions.

Metal (oxy)hydroxides (MO H, M = Fe, Co, Ni, and mixtures thereof) are important materials in electrochemistry. In particular, MO H are the fastest known catalysts for the oxygen evolution reaction (OER) in alkaline media. While key descriptors such as overpotentials and activity have been thoroughly characterized, the nanostructure and its dynamics under electrochemical conditions are not yet fully understood. Here, we report on the structural evolution of NiCoO H nanosheets with varying ratios of Ni to Co, in operando using atomic force microscopy during electrochemical cycling. We found that the addition of Co to NiO H nanosheets results in a higher porosity of the as-synthesized nanosheets, apparently reducing mechanical stress associated with redox cycling and hence enhancing stability under electrochemical conditions. As opposed to nanosheets composed of pure NiO H, which dramatically reorganize under electrochemical conditions to form nanoparticle assemblies, restructuring is not found for NiCoO H with a high Co content. NiFeO H nanosheets show high roughness as-synthesized which increases during electrochemical cycling while the integrity of the nanosheet shape is maintained. These findings enhance the fundamental understanding of MO H materials and provide insight into how nanostructure and composition affect structural dynamics at the nanoscale.

Dye-sensitized solar cells constitute a promising approach to sustainable and low-cost solar energy conversion. Their overall efficiency crucially depends on the effective coupling of the photosensitizers to the photoelectrode and the details of the dye's energy levels at the interface. Despite great efforts, the specific binding of prototypical ruthenium-based dyes to TiO2, their potential supramolecular interaction, and the interrelation between adsorption geometry and electron injection efficiency lack experimental evidence. Here we demonstrate multiconformational adsorption and energy level alignment of single N3 dyes on TiO2 anatase (101) revealed by scanning tunnelling microscopy and spectroscopy. The distinctly bound molecules show significant variations of their excited state levels associated with different driving forces for photoelectron injection. These findings emphasize the critical role of the interfacial coupling and suggest that further designs of dye-sensitized solar cells should target a higher selectivity in the dye-substrate binding conformations in order to ensure efficient electron injection from all photosensitizers.