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A major goal of energy research is to use visible light to cleave water directly, without an applied voltage, into hydrogen and oxygen. Since the initial reports of the ultraviolet (UV) activity of TiO2 and SrTiO3 in the 1970s, researchers have pursued a fundamental understanding of the mechanistic and molecular-level phenomena involved in photo-catalysis. Although it requires UV light, after four decades SrTiO3 is still the gold standard for splitting water. It is chemically stable and catalyzes both the hydrogen and the oxygen reactions without applied bias. While ultrahigh vacuum (UHV) surface science techniques have provided useful insights, we still know relatively little about the structure of electrodes in contact with electrolytes under operating conditions. Here, we report the surface structure evolution of a SrTiO3 electrode during water splitting, before and after training with a positive bias. Operando high-energy X-ray reflectivity measurements demonstrate that training the electrode irreversibly reorders the surface. Scanning electrochemical microscopy (SECM) at open circuit correlates this training with a tripling of the activity toward photo-induced water splitting. A novel first-principles joint density-functional theory (JDFT) simulation constrained to the X-ray data via a generalized penalty function identifies an anatase-like structure for the more active, trained surface.
Titanium-island formation on graphene as a function of defect density is investigated. When depositing titanium on pristine graphene, titanium atoms cluster and form islands with an average diameter of about 10nm and an average height of a few atomic
In this work, second-generation Car-Parrinello-based QM/MM molecular dynamics simulations of small nanoparticles of NbP, NbAs, TaAs and 1T-TaS$_2$ in water are presented. The first three materials are topological Weyl semimetals, which were recently
The k-space polarization structure and its strain response in SrTiO3 with rotational instability are studied using a combination of first-principles density functional calculations, modern theory of polarization, and analytic Wannier-function formula
Heterostructures made of transition metal oxides are new tailor-made materials which are attracting much attention. We have constructed a 6-band k.p Hamiltonian and used it within the envelope function method to calculate the subband structure of a v
Many-body descriptors are widely used to represent atomic environments in the construction of machine learned interatomic potentials and more broadly for fitting, classification and embedding tasks on atomic structures. It was generally believed that