S, Na Co-Doped Graphitic Carbon Nitride/Reduced Graphene Oxide Hollow Mesoporous Spheres for Photoelectrochemical Catalysis Application

As an environmentally friendly visible-light-responsive and metal-free photocatalyst, the photoelectrochemical (PEC) performance of graphitic carbon nitride (CN) has still been limited by its large optical band gap, low absorption of light, and inefficient transfer of electron–hole carriers. Herein, we report an S, Na co-doped CN/reduced graphene oxide (rGO) (S, Na-CN/rGO) hollow mesoporous sphere (HMS) prepared by supramolecular preorganization of monomers. The as-prepared S, Na-CN/rGO HMS is uniform with a diameter of ∼2 μm and exhibits a high specific surface area up to 92.3 m2g–1, a narrow band gap of 2.26 eV, and a high PEC performance with a photocurrent density of 14.04 μA/cm2, which is 78-fold of bulk CN (0.18 μA/cm2). The significantly enhanced PEC performance is attributed to the synergistic effect of enhanced light absorption by the multiple reflections of incident light in the unique HMS structure, the changes of the electronic structure by S, Na co-doping, and the well-conduced rGO layers in CN. The results have provided a way for realizing the practical photoelectrochemical catalysis application of CN.