Strongly Coupled Metal Oxide/Reassembled Carbon Nitride/Co–Pi Heterostructures for Efficient Photoelectrochemical Water Splitting

The photoelectrochemical application of carbon nitride is extremely exciting because of the meta-free components, low cost, nontoxicity, and appropriate band positions. To construct carbon nitride-based heterostructures, a conventional ultrasonic exfoliation method is usually used to fabricate dispersion of ultrathin nanosheets. However, the outstretched structure and the poor dispersity inevitably result in the poor interfacial contact between different materials. To solve this problem, hydrolyzed carbon nitride suspension was used as a homogeneous precursor for the fabrication of composite photoanodes. The in situ reassembly of one-dimensional nanofibers resulted in the formation of uniform and ultrathin carbon nitride nanoarchitectures on the surface of Fe₂O₃ nanorod arrays. Because of the strongly coupled interfaces and the deposition of Co-Pi water oxidation cocatalysts, the as-synthesized heterostructured photoanodes exhibited three-fold increased photocurrent density and good stability, compared to pristine Fe₂O₃. The significantly improved photoactivity of the Fe₂O₃/reassembled carbon nitride/Co-Pi heterostructures was ascribed to the decreased interfacial conductivity and facilitated charge separation. This material designing strategy was further used to construct TiO₂/carbon nitride, ZnO/carbon nitride, and WO₃/carbon nitride heterostructures. The incorporation of hydrolyzed carbon nitride could remarkably enhance the photoelectrochemical performance of these metal oxide photoanodes. Thus, this work provides a new paradigm for designing carbon nitride-based composite nanostructures for efficient and stable solar fuel production.