Surface Activation of the g-C3N4 Bilayer by π-Conjugation and Interlayer Orbital Interaction to Promote OER and HER

A novel, eco-friendly, polymorphic graphitic carbon nitride (g-C3N4) bilayer with its potential application in photoresponsive and physicochemical properties enhanced due to interlayer coupling lacks investigation of different stacking configurations, interlayer atomic superposition, and their effect on photoactive reaction sites. Using the hybrid density functional theory, structural, electronic, optical, and photocatalytic properties of nine spatially modified bilayers referred to as S0–S8, together with site-dependent oxygen/hydrogen evolution reactions (OER/HER) on the most photoactive bilayer (S3), have been explored in this work. vdW bilayers arranged considering all possibilities of interlayer atom–atom/atom–bond alignment along with the upper layer rotated by 0° (AA) and 180° (AB) on energy and force minimization are classified into planar (corrugated) geometry with band gap decrement (increment) compared to the monolayer, indicating the role of π-delocalization. Increased mobility, feasible surface migration, and reduced rate of recombination for photogenerated charge carriers in S3 along with the highest optical absorbance indicated its importance over monolayer and other bilayer configurations. Among the different active reaction sites, the best suitable site on S3 reveals 2 and 3 (20) times drop in value of overpotential for OER and HER (with an additional H2O molecule), respectively, against the monolayer. Current analysis displays efficient charge carrier separation, in which charge transfer within the bilayer on intermediate adsorption and formation of an interfacial electric field illustrates the stepwise reaction mechanism and proclaims the synergistic effect of π-conjugation and interlayer orbital interaction for surface activation and improved photocatalytic activity of the g-C3N4 bilayer as compared to the monolayer.