Facile fabrication of a metal-free ²D–²D Nb₂CTx@g-C₃N₄ MXene-based Schottky-heterojunction with the potential application in photocatalytic processes

Clean energy production and environmental detoxification through photocatalysis have received widespread attention due to their efficiency and capability to address global energy and environmental related calamities. Moreover, graphitic carbon nitride (g-C₃N₄) and many other single-semiconductor based photocatalysts have been widely explored; however, their performance is still unsatisfactory. Herein, the engineering of g-C₃N₄ as a primary photocatalyst interlayered with niobium carbide (Nb₂CTx) MXene co-catalyst for the formation of efficient photo-responsive Schottky-heterojunction photocatalyst is demonstrated. Visible-light absorption of g-C₃N₄ is proportional to the Nb₂CT_x contents. Moreover, g-C₃N₄ energy bandgap was significantly lowered from 2.61 eV to 2.19, 2.08, and 2.32 eV for 1, 3, and 5 wt% of Nb₂CT_x loaded onto g-C₃N₄, respectively. Nb₂CT_x MXene as a co-catalyst allows a formation of an efficient photocatalyst with high potential to eliminate the use of costly noble metals. The devised Schottky-junction restrained the electron recombination rates threefold relative to the pristine g-C₃N₄. The conduction band potential of g-C₃N₄ and the composites were observed to be more positive in relation to the standard reduction potential of O₂/•O₂^- (−0.33 V) CO₂/CO (−0.53 V), CO₂/CH₄ (−0.24 V), H₂/H⁺ (0.0 V), signifying its merits potentials for photocatalysis. The observed charge carriers with more negative reduction potential facilitates efficient photocatalytic reactions, particularly in hydrogen production and catalytic transformation of carbon dioxide into useful sources of energy. Fabricating a heterostructure between g-C₃N₄ and Nb₂CT_x MXene demonstrates the feasibility of facile preparation of photocatalysts with merit features due to synergistic catalytic effects.