2D Honeycomb-Kagome Polymer Tandem as Effective Metal-Free Photocatalysts for Water Splitting.

On the basis of first-principles calculations, the potential of applying 2D honeycomb-kagome polymers made of heteroatom-centered triangulene derivatives to photocatalyze water splitting is explored. The designed 2D polymers possess indirect bandgaps in the range of 1.80-2.84 eV and show pronounced light absorption in the ultraviolet and visible region of the solar spectrum. With suitable band edge alignment, the examined N- and B-center polymers can generate sufficient photon-excited electrons and holes to activate the hydrogen and oxygen evolution reactions, respectively. The combination of lattice-inherent band features (flat bands) with chemical functionalization (potential shift due to heteroatoms) makes it possible to construct tandem cells with suppressed electron/hole recombination for effective overall water splitting. In addition, there is a potential difference between the half-electrodes that can be utlized to power​ auxiliary components in self-sufficient photocatalyzers.