Caged supramolecular systems are promising hosts for guest inclusion, separation, and stabilization. Well-studied examples are mainly metal-coordination-based or covalent architectures. An anion-coordination-based cage that is capable of encapsulating halocarbon guests is reported for the first time. This A4L4-type (A=anion) tetrahedral cage, [(PO4)4L4](12-), assembled from a C3-symmetric tris(bisurea) ligand (L) and phosphate ion (PO4(3-)), readily accommodates a series of quasi-tetrahedral halocarbons, such as the Freon components CFCl3, CF2Cl2, CHFCl2, and C(CH3)F3, and chlorocarbons CH2Cl2, CHCl3, CCl4, C(CH3)Cl3, C(CH3)2Cl2, and C(CH3)3Cl. The guest encapsulation in the solid state is confirmed by crystal structures, while the host-guest interactions in solution were demonstrated by NMR techniques.

The perovskite-related oxynitride SrTaO 2 N is a prospective photoanode candidate with favorable band-edge positions. We have synthesized SrTaO 2 N nanowires with roughened surfaces by a hydrothermal process on a tantalum substrate and nitridation at 1273 K under flowing ammonia and hydrogen. The nanowires were coated with a ferrihydrite holestorage layer for photoelectrochemical water oxidation under AM 1.5G illumination in 0.1 M NaOH electrolyte (pH 13). The nanowires exhibit an electronic band gap of 2.32 eV, and the photocorrosion can be decreased with ferrihydrite coating. In the presence of Na 2 SO 3 as a hole scavenger, the nanowires do not yield higher photocurrent. This indicates that the limiting factors for hole extraction are processes occurring in the bulk instead of at the semiconductor−electrolyte interface. Our work is the first trial of a SrTaO 2 N photoanode based on nanowires and may also be promising for other quaternary oxynitride semiconductors to achieve a one-dimensional morphology.

CuWO is a photoanode candidate in neutral pH, and manganese-based oxygen evolution reaction electrocatalysts are of high interest due to their low price and low toxicity. Considering the unexplored chemistry of transition-metal carbodiimides/cyanamides for the PEC water oxidation, we investigated MnNCN as an electrocatalyst for CuWO under AM 1.5G illumination in potassium phosphate electrolyte (pH 7). Surface functionalization of CuWO photoanodes with MnNCN increased the photocurrent from 22 to 30 μA cm at 1.23 V vs RHE. Complementary structural analysis by means of XRD and XPS revealed that MnNCN forms a core-shell structure MnNCN@MnPO in phosphate electrolyte and mimics a manganese phosphate electrocatalyst. As such, the surface chemistry of MnNCN significantly differs from previous studies on the cobalt analogue (CoNCN). A separately prepared MnNCN electrode developed a small but detectable photocurrent due to photogenerated holes inside the semiconducting carbodiimide core of the MnNCN@MnPO structure.

Sunlight can be used to split water into hydrogen and oxygen by means of a photoelectrochemical (PEC) cell. Oxide nanostructures in heterojunction geometry, consisting of anisotropic WO 3 nanostructures coated with a second semiconductor having a narrower band gap, such as α-Fe 2 O 3 , have emerged as prospective photoanodes. Herein, the integration of monodisperse CoPd nanocrystals (NCs) with α-Fe 2 O 3 and WO 3 /α-Fe 2 O 3 heterojunction semiconductor nanostructures for PEC water oxidation is reported. Depositing CoPd NCs on the [a]

We investigated CuWO 4 as a promising photoanode and its surface functionalization with Ag 2 NCN. The composite photoanode displays a synergetic effect between its constituents during photoelectrochemical (PEC) water oxidation. After placing Ag 2 NCN particles on the CuWO 4 thin film, the photocurrent density increases from 15 to 45 μA cm −2 at 1.23 V vs reversible hydrogen electrode (RHE) in phosphate buffer electrolyte at pH 7 under simulated AM1.5 G illumination. The different positions of the band edges of CuWO 4 and Ag 2 NCN favor charge carrier separation at their interface. Upon illumination, photogenerated electrons of both semiconductors are transferred to the conduction band and can migrate to the counterelectrode. The higher position of the conduction band edge of Ag 2 NCN allows its electrons to be injected into the conduction band of CuWO 4 . Simultaneously, holes from the cyanamide are blocked, because the valence band edge position of CuWO 4 is positioned lower than for Ag 2 NCN. This results in more efficient charge separation and hole collection efficiencies. Herein, we emphasize the potential of carbodiimides and cyanamides in the design of photoelectrodes beyond oxide and nitride semiconductors.