In spite of the enormous promise that polymeric carbon nitride (PCN) materials hold for various applications, the fabrication of high-quality, binder-free PCN films and electrodes has been a largely elusive goal to date. Here, we tackle this challenge by devising, for the first time, a water-based solÀ gel approach that enables facile preparation of thin films based on poly(heptazine imide) (PHI), a polymer belonging to the PCN family. The solÀ gel process capitalizes on the use of a water-soluble PHI precursor that allows formation of a non-covalent hydrogel. The hydrogel can be deposited on conductive substrates, resulting in formation of mechanically stable polymeric thin layers. The resulting photoanodes exhibit unprecedented photoelectro-chemical (PEC) performance in alcohol reforming and highly selective (~100 %) conversions with very high photocurrents (> 0.25 mA cm À 2 under 2 sun) down to < 0 V vs. RHE. This enables even effective PEC operation under zero-bias conditions and represents the very first example of a 'soft matter'-based PEC system capable of bias-free photoreforming. The robust binder-free films derived from solÀ gel processing of watersoluble PCN thus constitute a new paradigm for high-performance 'soft matter' photoelectrocatalytic systems and pave the way for further applications in which high-quality PCN films are required.

Despite their technological importance for water splitting, the reaction mechanisms of most water oxidation catalysts (WOCs) are poorly understood. This paper combines theoretical and experimental methods to reveal mechanistic insights...

Cobaloximes are promising, earth-abundant catalysts for the light-driven hydrogen evolution reaction (HER). Typically, these cobalt(III) complexes are prepared in situ or employed in their neutral form, for example, [Co(dmgH) 2 (py) Cl], even though related complex salts have been reported previously and could, in principle, offer improved catalytic activity as well as more efficient immobilization on solid support. Herein, we report an interdisciplinary investigation into complex salts [Co(dmgH) 2 (pyWe describe their strategic syntheses from the commercially available complex [Co(dmgH) 2 (py)Cl] and demonstrate that these double and single complex salts are potent catalysts for the light-driven HER. We also show that scanning electrochemical cell microscopy can be used to deposit arrays of catalysts [Co(dmgH) 2 (py py)Cl] on supported and free-standing amino-terminated ~1-nm-thick carbon nanomembranes (CNMs). Photocatalytic H 2 evolution at such arrays was quantified with Pd microsensors by scanning electrochemical microscopy, thus providing a new approach for catalytic evaluation and opening up novel routes for the creation and analysis of "designer catalyst arrays", nanoprinted in a desired pattern on a solid support.

To date most studies focusing on light‐driven water splitting for green energy conversion schemes depend on bulk analyses of the produced hydrogen using, e. g., head‐space gas chromatography. In this contribution, we present the fabrication of Pd‐modified microelectrodes for in situ electrochemical hydrogen measurements using de‐alloyed Au−Ni microelectrodes. Stability studies and pH‐dependent investigations revealed the stability of these microsensors over a period of seven days, and confirmed their applicability in a pH range of 3–10 with a limit of detection (LOD)<1 μmol/L. First in situ proof‐of‐principle electrochemical imaging of hydrogen generated at a microelectrode and operando studies of hydrogen evolution at earth‐abundant cobalt hydrogen evolution catalysts using the developed Pd‐microsensors in combination with scanning electrochemical microscopy (SECM) demonstrated the potential of these microsensors for operando studies in light‐driven heterogeneous catalysis.