Polymeric carbon nitride-based photocathodes for visible light-driven selective reduction of oxygen to hydrogen peroxide

Polymeric carbon nitrides (PCN) are sustainable, tunable, non-toxic and chemically stable materials that represent highly promising heterogeneous photocatalysts for light-driven hydrogen peroxide production via selective reduction of dioxygen. However, most of the studies on photocatalytic H2O2 production using PCN-based photocatalysts reported so far have used PCN powder suspensions and have been carried out in the presence of additional (sacrificial) electron donors, such as aliphatic or aromatic alcohols. Herein, we report the first multicomponent hybrid photocathode based on PCN that is capable of selective reduction of dioxygen to H2O2 under visible light irradiation (420 nm LED). A comparative analysis of various photocathode architectures is carried out using electronic absorption spectroscopy, surface photovoltage spectroscopy, open-circuit photopotential spectroscopy, and photocurrent measurements, including in-situ detection of formed H2O2 using microelectrodes. Notably, the ability of PCN-based photocathodes to catalyze the light-driven reduction of O2 to H2O2 in the absence of any additional electron donor is unambiguously demonstrated. Our study thus highlights the intrinsic nature of the photocatalytic activity of PCN in H2O2 production, and paves the way for the development of further PCN-based photocathodes in which PCN could be coupled with more effective light absorbers to increase the overall performance.