Metal oxide libraries for photoanodes for the oxygen evolution reaction (OER) were generated by printing a metal salt solution in an array layout, followed by calcination to yield 22 ternary metal oxide systems. The libraries included a ternary metal cation system based on CuWO4 with one out of eight transition or posttransition metal ions Cr, Mn, Fe, Co, Ni, Zn, Bi, and Ga in different overall atomic ratios. The photocatalyst libraries were screened by scanning photoelectrochemical microscopy for the highest anodic photocurrents. Array elements that showed promising performance were printed in another set of eight libraries with smaller increments of overall composition. Improved performance with respect to CuWO4 was found for Ga, Co, and Ni as the third element. A comparison of the most active composition of those arrays within one library showed the highest activity for Cu48Ga3W49O x . Printing spots of identical composition (Cu48Ga3W49O x , Cu44Ni9W47O x , and Cu44Co9W47O x ) over a larger area facilitated further characterization by X-ray photoelectron spectroscopy ultraviolet photoelectron spectroscopy (UPS), X-ray diffraction, scanning electron microscopy, chopped light voltammetry, and scanning electrochemical microscopy for the OER. High and stable steady-state photocurrents were generated in a photoelectrochemical cell for all three electrodes even at a low constant bias voltage. The best overall photoanode composition Cu48Ga3W49O x showed currents that were 36 times higher than the currents of the binary Cu50W50O x system. Significant n-doping was found by UPS valence band spectra for Ga-containing materials.

Wet-chemical syntheses for quasi two-dimensional (2D) transition metal dichalcogenides (TMDs) have emerged as promising methods for straightforward solution-processing of these materials.However, photoluminescence properties of colloidal TMDs are virtually unexplored due to the typically non-emitting synthesis products. In this work, we demonstrate room temperature microphotoluminescence spectroscopy on delicate ultrathin colloidal WS 2 nanosheets synthesized from WCl 6 and elemental sulfur in oleic acid and oleylamine at 320 °C for the first time. Both, monoand multilayer photoluminescence is observed, revealing comparable characteristics to exfoliated TMD monolayers and underpinning the high quality of colloidal WS 2 nanosheets. In addition, a promising long-term air-stability of colloidal WS 2 nanosheets is observed and the control of their photodegradation under laser excitation is identified as a challenge for further advancing nanosheet monolayers. Our results render colloidal TMDs as easily synthesized and highly promising 2D semiconductors with optical properties fully competitive with conventionally fabricated ultrathin TMDs.

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A new dipping robot is presented for the execution of layer‐by‐layer (LbL) deposition procedures for the modification of electrode surfaces. It is composed of low‐budget parts broadly available three‐dimensional (3D) printer. New extra hardware components produced by 3D printing and the open‐source software can turn such a device into a flexible dipping robot. The required changes in code as well as the printing instructions for the changed hardware components are documented and are made freely available together with tools that allow customizing LbL coating processes. The potential of this very flexible instrumentation is exemplified by a redox‐active film of nickel hexacyanoferrate on a gold electrode modified by a monolayer of 3′‐mercaptobiphenyl‐carbonitrile. Scanning electron microscopy confirm the absence of micometer‐sized cracks. It shows the typical voltammetric behavior of that material.

A flexible, electron-rich building block was integrated into the backbone of a metal−organic framework with a MOF-74 topology. The building block comprises a central anthracene core connected to acetylene groups. Solvothermal synthesis with Mn 2+ yields a highly crystalline anthracene−ethynebased MOF-74 structure. It shows an unusual helical rod-like morphology, exhibiting visible light absorption and photoluminescence.