Defect-rich N-doped CeO2 supported by N-doped graphene as a metal-free plasmonic hydrogen evolution photocatalyst

Abstract

Heteroatom doping into metal oxides advantageously modulates optoelectronic properties and provides promising possibilities for efficient light-to-energy conversion. Herein, nitrogen-doped ceria (N-CeO₂) nanoparticles are prepared and then coupled with nitrogen-doped graphene (N-Gr) to create an active and long-lasting N-CeO₂/N-Gr heterocatalyst. Optoelectronic features of N-doping materials (e.g., plasmon) are significantly improved toward the visible-light region, particularly for 3.9% N-CeO₂/N-Gr nanocomposites. Namely, the 3.9% N-CeO₂ possesses numerous catalytic active defects (N states, oxygen vacancy, and Ce³⁺ species), leading to a narrow bandgap energy and to the improved plasmonic properties of the ceria host, while the N-Gr preferably serves as an electron scavenger to collect plasmon-generated hot electrons migrating from 3.9% N-CeO₂ to drive photocatalytic reactions under the irradiation of visible-light. Resultantly, the 3.9% N-CeO₂/N-Gr photocatalyst delivers an impressive hydrogen evolution reaction (HER) rate of 3.7 μmol mg_cat⁻¹ h⁻¹ under visible-light, which is 2.0- and 8.2-fold greater than those obtained from 3.9% N-CeO₂ and CeO₂ ones, respectively. Additionally, the combination of 3.9% N-CeO₂ and N-Gr synergistically produces a long-lasting plasmonic HER photocatalyst system. Metal-free plasmonic N-doped oxides supported by N-doped graphene pave a promising pathway for efficient light-to-hydrogen fuel production accordingly.