Carbon nitrides have emerged as a new class of functional materials for a wide range of energy and environmental applications due to their chemical, photophysical and catalytic properties as well as their low-price, facile synthesis and stability.

A general synthesis of carbon nitride (CN) films with extended optical absorption, excellent charge separation under illumination, and outstanding performance as a photoanode in water-splitting photoelectrochemical cells is reported. To this end, we introduced a universal method to rapidly grow CN monomers directly from a hot saturated solution on various substrates. Upon calcination, a highly uniform carbon nitride layer with tuned structural and photophysical properties and in intimate contact with the substrate is obtained. Detailed photoelectrochemical and structural studies reveal good photoresponse up to 600 nm, excellent hole extraction efficiency (up to 62%) and strong adhesion of the CN layer to the substrate. The best CN photoanode demonstrates a benchmark-setting photocurrent density of 353 µA cm⁻² (51% faradaic efficiency for oxygen), and external quantum yield value above 12% at 450 nm at 1.23 V versus RHE in an alkaline solution, as well as low onset potential and good stability.

We studied the chemical, optical and catalytic properties of metal (Pt, Pd, Ag, Au)–Cu₂O core–shell nanoparticles grown via a simple and reproducible approach which utilizes aqueous-phase reactions at room temperature. We were able to control the thickness of the Cu₂O shell and examine the effect of the core's shape and size on the structure and properties of the hybrid nanocrystals. We also studied the optical properties of the hybrid nanocrystals, in particular the effect of the Cu₂O shell thickness on the frequency of the plasmon of gold nanorods. In addition, the catalytic activity of the hybrid nanostructures was examined by testing the reduction reaction of 4-nitrophenol with NaBH₄. Finally, the hybrid metal–Cu₂O nanostructures were used as templates to form the yolk–shell of metal–Cu₂S materials. The interface and the crystalline structures of the four hybrid nanostructures were extensively characterized by high resolution transmission electron microscopy (HRTEM), energy-filtered TEM (EFTRM) and X-ray diffraction (XRD).