Efficient hybrid capacitive deionization with MnO2/g-C3N4 heterostructure: Enhancing Mn dz2 electron occupancy by interfacial electron bridge for fast charge transfer

Abstract

While MnO2 has been identified as a potent agent in the desalination process, its efficacy is significantly impeded by its inherent poor electrical conductivity and substantial ion diffusion barriers. By orchestrating an interfacial electron bridge within the MnO2/g-C3N4 heterostructure, reinforced through Npz-Mndz2 orbital hybridization, we have managed to significantly boost both SAC and SAR in the HCDI process. The reinforced Npz-Mndz2 orbital hybridization triggers a substantial electron transition from g-C3N4 to MnO2, culminating in a high Mn dz2 electron occupancy. Further analysis reveals the formation of a MnN chemical bond at the MnO2/g-C3N4 interface, operating as an essential electron transfer bridge from g-C3N4 to MnO2. This process concurrently initiates a rise in the Mn dz2 orbital energy level, equipping the Mn dz2 electron with superior redox activity. With these enhancements, the manufactured MnO2/g-C3N4 exhibits exemplary performance, boasting an improved SAC of 68 mg g−1 and SAR of 3.6 mg g−1 min−1 with a decreased energy consumption of 0.7224 kWh kg−1 at 1.2 V. This innovative work offers an unconventional roadmap for activating electron redox activity and thereby accelerating charge transfer in transition metal oxides.