In this study, Ti@Ni0.85Se electrodes with a triple hierarchy architecture were designed, and their applications in electrocatalytic water splitting were studied. The 3D electrode is comprised of three types of structures including the bottom square Ti mesh structure as the conductive substrate, a vertical and uniform Ni0.85Se nanosheet arrays structure in the intermediate section, and the topmost Ni0.85Se flower structure. This triple hierarchy architecture is binder‐free, conductive, and has a particular feature of enlarged surface areas, exposing more active sites, promoting mass‐ and charge‐transfer, and accelerating dissipation of gases generated during water electrolysis. Moreover, DFT calculations confirmed that the Ni0.85Se possesses metallic character, which further promotes the charge transfer of the electrocatalyst. Benefiting from this special structure and metallic character, the electrode displays a superior activity of 10 mA cm−2 at 120 mV hydrogen evolution reaction overpotential and 30 mA cm−2 at 270 mV oxygen evolution reaction overpotential. By using this electrode as a bifunctional electrocatalyst, an alkali electrolyzer affords a water splitting current of 10 mA cm−2 at a cell voltage of 1.66 V.

A CdWO/BiOCO core-shell heterostructure photocatalyst was fabricated via a facile two-step hydrothermal process. Flower-like BiOCO was synthesized and functioned as the cores on which CdWO nanorods were coated as the shells. Photoluminescence (PL) spectra and electron paramagnetic resonance (EPR) demonstrate that the CdWO/BiOCO core-shell heterostructure photocatalyst possesses a large amount of oxygen vacancies, which induce defect levels in the band gap and help to broaden light absorption. The photocatalyst exhibits enhanced photocatalytic activity for Rhodamine B (RhB), methylene blue (MB), methyl orange (MO), and colorless contaminant phenol degradation under solar light irradiation. The heterostructured CdWO/BiOCO core-shell photocatalyst shows drastically enhanced photocatalytic properties compared to the pure CdWO and BiOCO. This remarkable enhancement is attributed to the following three factors: (1) the presence of oxygen vacancies induces defect levels in the band gap and increases the visible light absorption; (2) intimate interfacial interactions derived from the core-shell heterostructure; and (3) the formation of the n-n junction between the CdWO and BiOCO. The mechanism is further explored by analyzing its heterostructure and determining the role of active radicals. The construction of high-performance photocatalysts with oxygen vacancies and core-shell heterostructures has great potential for degradation of refractory contaminants in water with solar light irradiation.

Flower-like CdWO4–BiOCl–Bi2WO6 ternary hybrid photocatalyst shows enhanced photocatalytic activity due to dye sensitization and its cascade structure.