What Limits the Stability Performance of Polymeric Carbon Nitride Photoanode for Photoelectrochemical Water Splitting?

Although many researches have been reported about the high performance of polymeric carbon nitride (PCN) photoanode, but it is still limited by poor stability. In this work, PCN nanosheets photoanode is used as a platform to investigate the sources of this issue. Through a combination of photoelectrochemical, X-ray Photoelectron Spectroscopy (XPS), and Potentiostatic Electrochemical Impedance Spectroscopy (PIES) measurements, it is shown that amounts of C═O bonds will form on the surface of PCN photoanodes, which limited the separation of the photogenerated carriers. To solve this problem, the TiO₂ is deposited on PCN photoanode (named as PCN/TiO₂) to improve the stability. And the PEC water splitting studies revealed that the stability of PCN/TiO₂ photoanode is improved significantly as its photocurrent density can still maintain 90% after 3 h of reaction. This study provides a new way to understand the mechanism for the performance decrease of PCN photoanode and hope to inspire more powerful strategies to improve PCN photoanode stability.