Significant Impact of Exposed Facets on the BiVO4 Material Performance for Photocatalytic Water Splitting Reactions

The impact of the four predominant (010), (110), (001), and (121) exposed facets obtained experimentally for monoclinic BiVO₄ on its photocatalytic performance for water splitting reactions is investigated on the basis of the hybrid density functional theory including the spin-orbit coupling. Although their electronic structure is similar, their transport and redox properties reveal anisotropic characters based on the crystal orientation and termination. The particular role of each facet in proton reduction was correlated with the surface Bi coordination number and their geometrical distribution. Our work predicts the (001) facet as the only good candidate for both HER and OER, while the (010) facet is a fitting candidate for OER only. The (110) and (121) surfaces are acceptable candidates only for OER but less potential than (001) and (010). These outcomes will efficiently conduct experimentalists for an attentive design of facet-oriented BiVO₄ samples toward improving water oxidation and proton reduction.

Combinatorial Synthesis of Oxysulfides in the Lanthanum-Bismuth-Copper System

Establishing synthesis methods for a target material constitutes a grand challenge in materials research, which is compounded with use-inspired specifications on the format of the material. Solar photochemistry using thin film materials is a promising technology for which many complex materials are being proposed, and the present work describes application of combinatorial methods to explore the synthesis of predicted La-Bi-Cu oxysulfide photocathodes, in particular alloys of LaCuOS and BiCuOS. The variation in concentration of three cations and two anions in thin film materials, and crystallization thereof, is achieved by a combination of reactive sputtering and thermal processes including reactive annealing and rapid thermal processing. Composition and structural characterization establish composition-processing-structure relationships that highlight the breadth of processing conditions required for synthesis of LaCuOS and BiCuOS. The relative irreducibility of La oxides and limited diffusion indicate the need for high temperature processing, which conflicts with the temperature limits for mitigating evaporation of Bi and S. Collectively the results indicate that alloys of these phases will require reactive annealing protocols that are uniquely tailored to each composition, motivating advancement of dynamic processing capabilities to further automate discovery of synthesis routes.

Insights into the Impact of Native Defects on the Conductivity of CuVO3 Material for Photovoltaic Application: A First-Principles Computational Study

We report a theoretical study on the impact of native defects present in CuVO₃ material on its conductivity using first-principles calculations based on density functional theory. We find a low and direct band gap of 1.4 eV for the pristine cell together with relatively high solar absorption efficiency, high macroscopic dielectric constant, and delocalized orbital characters of photogenerated charge carriers. This result highlights CuVO₃ as a good candidate for photovoltaic application. Among the various explored native defects (including vacancies, interstitials, and antisites), we demonstrate that only those associated with O vacancies are shallow donors and with Cu vacancies are shallow acceptors, leading respectively to n-type and p-type conductivities under O-poor and O-rich growing conditions.

Bismuth Oxysulfide and Its Polymer Nanocomposites for Efficient Purification

The danger of toxic organic pollutants in both aquatic and air environments calls for high-efficiency purification material. Herein, layered bismuth copper oxychalcogenides, BiCuSO, nanosheets of high photocatalytic activity were introduced to the PVDF (Polyvinylidene Fluoride). The fibrous membranes provide an easy, efficient, and recyclable way to purify organic pollutant. The physical and photophysical properties of the BiCuSO and its polymer composite were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), ultraviolet-visible diffuse reflection spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), electron spin resonance (EPR). Photocatalysis of Congo Red reveals that the BiCuSO/PVDF shows a superior photocatalytic activity of a 55% degradation rate in 70 min at visible light. The high photocatalytic activity is attributed to the exposed active {101} facets and the triple vacant associates VBi‴VO••VBi‴. By engineering the intrinsic defects on the surface of bismuth oxysulfide, high solar-driven photocatalytic activity can be approached. The successful fabrication of the bismuth oxysulfide and its polymer nanocomposites provides an easy and general approach for high-performance purification materials for various applications.