Porous carbon nitride rods as an efficient photoanode for water splitting and benzylamine oxidation

Abstract

Controlling the properties of a polymeric carbon nitride (CN) layer during its in situ growth on a conductive substrate, including its directionality, morphology, specific surface area, and defects, is challenging because of the high temperature of the reaction and the substrate properties. Here, we report the growth of defect-rich, porous 1D CN with enhanced optical properties and photocatalytic activity by utilizing sophisticated supramolecular assemblies composed of melamine and HCl as starting precursors. The supramolecular assembly composition directs the 1D growth, and the presence of protonated amines in the precursor leads to partial condensation and defect generation. The 1D configuration, high specific surface area, and abundance of defects of the photoanode result in high photoelectrochemical activity for water and benzylamine oxidation. The new design of the CN photoanode leads to very low overpotential, good photocurrent density of 183 ± 8 μA cm⁻² at 1.23 V vs. reversible hydrogen electrode (RHE), with an incident photon to current efficiency (IPCE) of up to 10.5% and enhanced stability (retaining ∼62% activity) for 10 h. Moreover, the conversion of benzylamine into benzaldehyde and imine N-benzylideneaniline in the presence of O₂ reaches 56% compared to 16% for the reference CN photoanode.