Direct Photoelectric Storage of Solar Energy in C‐Rich Polymeric Carbon Nitride Cell: Mechanism and Performance Improvement

The photochargeable materials have drawn growing research interest for the application of direct photoelectric storage of solar energy. Carbon-rich conjugated carbon nitride polymers with hybrid pi-conjugated structure combining heptazine motifs with graphitic carbon rings have drawn a lot of attention for the extended conjugation length, tunable band gap, and 2D thin-layer structure. The carbon-rich polymeric carbon nitride (CPCN) with a band gap of 1.74 eV is successfully applied in direct photoelectric storage of solar energy. However, the ambiguous underlying mechanism limits the performance improvement. Herein, the relationship of microstructure and photoelectrochemical properties of the CPCN material is further investigated using the techniques including nuclear magnetic resonance spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and cyclic voltammetry. The influence of the ratio of conjugated C(sic)N-C to C(sic)C-C on the band edge positions of the CPCN material, which directly relates to electron transport paths of the photo-charging and discharging processes, is revealed. With the diffusion-controlled charge storage regime, the CPCN cell obtains a specific capacity of 44.6 C g(-1).