Molten Salt Modulation\nof Potassium–Nitrogen–Carbon\nfor the Breaking Kinetics Bottleneck of Photocatalytic Overall Water\nSplitting and Environmental Impact Reduction

Sluggish interfacial water dissociation and the O<sub>2</sub> evolution\nreaction (OER) kinetics are the main obstacles that limit the photocatalytic\noverall water-splitting performance. A molten salt modulation of potassium–nitrogen–carbon\nis herein demonstrated as the formation of highly crystalline potassium-doped\npoly­(triazine imide) (KPTI). The in situ X-ray diffraction patterns\nand theoretical calculation show that the KCl melt can significantly\nreduce the free energy for the polycondensation of triazine building\nblocks owing to the formation of a kinetically stable KPTI. Benefiting\nfrom the presence of potassium–carbon–nitrogen moiety,\nthe catalyst not only weakens the excitonic confinement to improve\nthe separation efficiency of photogenerated charge carriers but also\nenhances the stability of carbon sites by suppressing the undesired\nCO formation. Moreover, KPTI accelerates water dissociation\nby forming interfacial K·H<sub>2</sub>O clusters with an ordered\nstructure, which supplies sufficient protons for the H<sub>2</sub> evolution reaction and lowers the energy barrier to enhance the\nkinetics of OER. Therefore, a stable photocatalytic overall water-splitting\nperformance can be achieved over KPTI with a stoichiometric generation\nof products (H<sub>2</sub> and O<sub>2</sub>). Life cycle assessment\nshows that a carbon-neutral scenario can be achieved on KPTI production\nin the near term with an increase in green power in the electricity\ngrid.