(Invited) Carbon Nitride Layers As Light-Harvesting Semiconductors for Photoelectrochemical Cells

Abstract

Photoelectrochemical cells (PECs) have been developed as environmentally friendly systems that can directly utilize photogenerated electron-hole pairs for water splitting, fuel production, conversion of carbon dioxide, and pollutant degradation. Most reports on the photocatalytic or PEC hydrogen (H2) evolution via water splitting have focused on the H2 reduction half-reaction by generating on the photoanode oxygen or using sacrificial agents to consume the generated h+. Lately, much effort has been invested into synthesizing valuable chemicals on the photoanode while retaining the production of H2 on the cathode.Over the past few years, polymeric carbon nitrides (CN) have attracted widespread attention due to their outstanding electronic properties, which have been exploited in various applications, including photo- and electro-catalysis, heterogeneous catalysis, CO2 reduction, water splitting, light-emitting diodes, and PV cells. CN comprises only carbon and nitrogen, and it can be synthesized by several routes. Its unique and tunable optical, chemical, and catalytic properties, alongside its low price and remarkably high stability to oxidation (up to 500 °C), make it a very attractive material for photoelectrochemical applications. However, few reports regarded CN utilization in PECs due to the difficulty in acquiring a homogenous CN layer on a conductive substrate and our lack of a basic understanding of the intrinsic layer properties of CN.This talk will introduce new approaches to growing CN layers with altered properties on conductive substrates for photoelectrochemical applications. The growth mechanism and their chemical, photophysical, electronic, and charge transfer properties will be discussed. I will show the utilization of PEC with a CN-based photoanode as a stable and efficient platform for the oxidation of water or organic molecules to oxygen or added-value chemicals, respectively, with hydrogen co-production.