Low-Temperature Hydrogen Production via Water Conversion on Pt/TiO₂

Pt-supported TiO₂ catalysts have proved to be good catalysts for efficient hydrogen (H₂) production from photocatalytic water (H₂O) splitting and water–gas shift reactions. However, their origin for efficient H₂O conversion remains poorly understood. Here, we report a systematic study of low-temperature H₂ formation via H₂O conversion on Pt-deposited rutile-TiO₂(110) surfaces by means of spectroscopic and microscopic techniques in combination with first-principles calculations. We show that the low-temperature H₂ formation can occur facilely at ∼200 K via H₂O conversion on the Pt clusters/rutile-TiO₂(110) surfaces, which is initiated by H₂O dissociation at the surface defects, metal–oxide interfaces, and probably regular Ti⁴⁺ sites. More importantly, H₂O-assisted multistep H atom diffusion plays a crucial role for transferring H atoms toward Pt clusters, resulting in efficient H₂ evolution. These results enrich the understanding of H₂ formation via H₂O conversion on Pt/TiO₂ catalysts, which is helpful for understanding this reaction on other metal–oxide catalysts

α V

Many questions remain about the significance of structural features of integrin α(V)β(3) for its mechanism of activation. We have determined and re-refined, respectively, crystal structures of the α(V)β(3) ectodomain linked to C-terminal coiled-coils (α(V)β(3)-AB) or four transmembrane (TM) residues in each subunit (α(V)β(3)-1TM). The α(V) and β(3) subunits with four and eight extracellular domains, respectively, are bent at knees between the integrin headpiece and lower legs, and the headpiece has the closed, low-affinity conformation. The structures differ in occupancy of three metal binding sites in the βI domain. Occupancy appears related to the pH of crystallization, rather than to physiologic regulation of ligand binding at the central, metal-ion dependent adhesion site (MIDAS). No electron density was observed for TM residues and much of the α(V) linker. α(V)β(3)-AB and α(V)β(3)-1TM demonstrate flexibility in the linker between their extracellular and TM domains, rather than previously proposed rigid linkage. A previously postulated interface between the α(V) and β(3) subunits at their knees was also not supported, because it lacks high quality density, required rebuilding in α(V)β(3)-1TM, and differed markedly between α(V)β(3)-1TM and α(V)β(3)-AB. Together with variation in domain-domain orientation within their bent ectodomains between α(V)β(3)-AB and α(V)β(3)-1TM, the structures are compatible with the requirement of large structural changes, such as extension at the knees and headpiece opening, in conveying activation signals between the extracellular ligand-binding site and the cytoplasm