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An MnNCN-Derived Electrocatalyst for CuWO4 Photoanodes
- Davi, Martin, Mann, Markus, Ma, Zili, Schrader, Felix, Drichel, Andreas, Budnyk, Serhiy, Rokicinska, Anna, Kustrowski, Piotr, Dronskowski, Richard, Slabon, Adam
- Langmuir 2018 v.34 no.13 pp. 3845-3852
- X-ray diffraction, X-ray photoelectron spectroscopy, cobalt, cyanamides, electric current, electrodes, electrolytes, lighting, oxidation, oxygen production, pH, potassium phosphates, prices, toxicity
- CuWO₄ 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 CuWO₄ under AM 1.5G illumination in potassium phosphate electrolyte (pH 7). Surface functionalization of CuWO₄ photoanodes with MnNCN increased the photocurrent from 22 to 30 μA cm–² at 1.23 V vs RHE. Complementary structural analysis by means of XRD and XPS revealed that MnNCN forms a core–shell structure MnNCN@MnPOₓ 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@MnPOₓ structure.