As a first step towards a microscopic understanding of single-Pt atom-dispersed catalysts on non-conventional TiN supports, we present density-functional theory (DFT) calculations to investigate the adsorption properties of Pt atoms on the pristine TiN(100) surface, as well as the dominant influence of surface defects on the thermodynamic stability of platinized TiN. Optimized atomic geometries, energetics, and analysis of the electronic structure of the Pt/TiN system are reported for various surface coverages of Pt. We find that atomic Pt does not bind preferably to the clean TiN surface, but under typical PEM fuel cell operating conditions, i.e. strongly oxidizing conditions, TiN surface vacancies play a crucial role in anchoring the Pt atom for its catalytic function. Whilst considering the energetic stability of the Pt/TiN structures under varying N conditions, embedding Pt at the surface N-vacancy site is found to be the most favorable under N-lean conditions. Thus, the system of embedding Pt at the surface N-vacancy sites on TiN(100) surfaces could be promising catalysts for PEM fuel cells.

A defect engineering of inorganic solids garners great deal of research activities because of its high efficacy to optimize diverse energy-related functionalities of nanostructured materials. In this study, a novel in situ defect engineering route to maximize electrocatalytic redox activity of inorganic nanosheet is developed by using holey nanostructured substrate with strong interfacial electronic coupling. Density functional theory calculations and in situ spectroscopic analyses confirm that efficient interfacial charge transfer takes place between holey TiN and Ni−Fe-layered double hydroxide (LDH), leading to the feedback formation of nitrogen vacancies and a maximization of cation redox activity. The holey TiN−LDH nanohybrid is found to exhibit a superior functionality as an oxygen electrocatalyst and electrode for Li−O 2 batteries compared to its non-holey homologues. The great impact of hybridization-driven vacancy introduction on the electrochemical performance originates from an efficient electrochemical activation of both Fe and Ni ions during electrocatalytic process, a reinforcement of interfacial electronic coupling, an increase in electrochemical active sites, and an improvement in electrocatalysis/charge-transfer kinetics.

In this work, we present density-functional theory calculations to investigate the surface properties of TiN as a function of surface orientation and termination, as well as the influence of surface defects for various surface defect concentrations. We calculate both the surface energies (including vacancy formation) as a function of the nitrogen chemical potential, and plot the first-principles derived equilibrium crystal shape (ECS) under different growth conditions. We find that surface defects can considerably change the derived ECS of TiN (especially under nitrogen-lean conditions), highlighting the importance of surface defect consideration in modeling nanoparticle morphology.

CuRhO 2 in the delafossite structure is a promising, highly stable photocathode material for solar water splitting, yet the fundamental bulk and surface properties of CuRhO 2 that are relevant to such an application have rarely been studied. In this work, we present a comprehensive computational study of the bulk and majority (001) surface of CuRhO 2 using density functional theory at the meta-GGA and hybrid functional levels. For bulk CuRhO 2 , our results show a significant degree of hybridization between Rh, Cu, and oxygen states near the valence band maximum suggesting a high hole mobility in this material in comparison to other Cu-delafossite oxides. The typical Cu vacancy and Cu antisite defects are predicted to behave as shallow acceptors in bulk CuRhO 2 ; they do not trap charge carriers and should not act as electron− hole recombination centers under photoexcitation. The computed surface stability diagram under vacuum conditions shows that CuRhO 2 (001) typically exposes the Rh/O termination with empty surface states in the lower half of the band gap. Cu antisite defects can however form on this surface, leading to deep hole states that can trap electrons and favor the recombination of photoexcited carriers. Overall, the present results provide fundamental insight into the properties of intrinsic defects in the bulk and at the surface of CuRhO 2 . This knowledge is an essential basis for an investigation of the photo-electrochemical performance of this material.

The density and arrangement of oxygen vacancies (V O s) play an important role in tuning the physicochemical properties of TiO 2 for different technological applications, hence motivating significant interest in the characteristics of V O s' complexes and superstructures in this material. In this work we focus on the geometries and stabilities of V O s' aggregates in rutile (R-TiO 2 ) and anatase (A-TiO 2 ), the two most common TiO 2 polymorphs, using density functional theory (DFT) calculations with on-site Hubbard U repulsion. Through extensive exploration of various possible configurations, we identify the most favorable geometries of divacancies and larger V O s' complexes. We find that divacancies prefer to lie at second-nearest-neighbor trans positions in the same TiO 6 octahedron, and ordered chains and planar aggregates of V O s are energetically favorable over disordered noninteracting vacancies in both A-and R-TiO 2 . However, the energetic gain upon V O s' aggregation is much larger in R-TiO 2 than A-TiO 2 . As a result, vacancy complexes are stable at and above typical sample preparation and annealing temperatures (∼1000 K) in R-TiO 2 , whereas only one-dimensional chain structures are predicted to survive at those temperatures in anatase.