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An MnNCN-Derived Electrocatalyst for CuWO4 Photoanodes
Martin Davi1, Markus Mann1, Zili Ma1
1Institute of Inorganic Chemistry , RWTH Aachen University , Landoltweg 1 , D-52056 Aachen , Germany.
Langmuir : the ACS Journal of Surfaces and Colloids
|March 20, 2018
Summary
Manganese carbodiimide (MnNCN) enhances copper tungstate (CuWO4) photoanodes for water oxidation, increasing photocurrent. The MnNCN surface transforms into a manganese phosphate layer, improving catalytic activity in neutral pH conditions.
Area of Science:
- Materials Science
- Electrochemistry
- Photocatalysis
Background:
- Copper tungstate (CuWO4) is a promising photoanode material for neutral pH applications.
- Manganese-based electrocatalysts are attractive due to their affordability and low toxicity.
- The use of transition-metal carbodiimides/cyanamides for photoelectrochemical (PEC) water oxidation remains largely unexplored.
Purpose of the Study:
- To investigate manganese carbodiimide (MnNCN) as an electrocatalyst for CuWO4 photoanodes in PEC water oxidation.
- To understand the surface chemistry and structural evolution of MnNCN under operating conditions.
- To evaluate the performance enhancement of CuWO4 photoanodes functionalized with MnNCN.
Main Methods:
- Surface functionalization of CuWO4 photoanodes with MnNCN.
- Photoelectrochemical measurements under AM 1.5G illumination in potassium phosphate electrolyte (pH 7).
- Structural and surface analysis using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS).
Main Results:
- Surface functionalization with MnNCN increased the photocurrent of CuWO4 photoanodes from 22 to 30 μA cm⁻² at 1.23 V vs RHE.
- XRD and XPS analysis revealed the formation of a core-shell MnNCN@MnPOx structure, mimicking a manganese phosphate electrocatalyst.
- The surface chemistry of MnNCN in phosphate electrolyte differs significantly from its cobalt analogue (CoNCN).
- A standalone MnNCN electrode exhibited a detectable photocurrent, indicating semiconducting properties within the MnNCN@MnPOx structure.
Conclusions:
- MnNCN acts as an effective electrocatalyst for CuWO4 photoanodes, enhancing PEC water oxidation efficiency.
- The in-situ formation of a manganese phosphate layer on MnNCN is crucial for its catalytic performance.
- MnNCN presents a novel and promising material for PEC water splitting applications.
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