Boosting photocatalytic nitrogen reduction to ammonia by dual defective -C[tbnd]N and K-doping sites on graphitic carbon nitride nanorod arrays

Abstract

Bi-defective g-C3N4 (K and -CN) nanorod arrays with favorable light absorption through multiple light scattering/reflections were designed for photocatalytic N2 reduction. The highest record of NH3 production, 23.5 mmol/(h·gcat), was achieved when dual defects are present at the nanoarrays without any cocatalysts, which is about two orders higher than its counterpart. The N2 reduction rate is proportional to -CN, unveiling its role as active sites. Its synergistic effect with K was observed. Theoretical calculations support that -CN site is crucial to N2 activation by donating electrons, while cation like K center traps electrons. Consequently, modification with such dual defects in conjunction with nanoarray configuration creates a favorable electron-dominated structure to overcome the energy barrier for activating inert nitrogen, enhancing charge separation and light absorption effectively. The present work underlines the impetus of defects engineering and nanoarray configuration for the rational design of active photocatalysts for efficient N2 fixation.