Engineering 2D g-C3N4 for Enhanced Photocatalytic Water Purification: Impact of Post-Processing on Activity Enhancement

Abstract

In recent decades, g-C3N4 has emerged as a potential candidate amongst the 2D materials revolutionizing the materialistic approach towards water remediation applications. Being mostly accessible semiconductors by their excellent conductivity but facing challenges in their bulk counterparts prone to faster recombination rates, fewer active sites for adsorption, and poor light absorptive capacity. To address these drawbacks and develop an efficient metal-free photocatalyst with only g-C3N4 is the prime focus of this research. The main aim is directed towards the engineering of metal-free, pristine g-C3N4 sheets from its bulk form to ultrathin nanosheets (NS), partially exfoliated nanosheets (PS) by two scalable post-processing methods (Thermal exfoliation, mechano-hydrothermal) in absence of dopants, heterojunctions or co-catalysts. The engineered g-C3N4 sheets aid straight comparison of photocatalytic enhancement exclusively grounded on tailored morphologies enabling a precise benchmark for adsorption, charge dynamics and ROS mediated degrdation. The formed bulk g-C3N4 (BS), ultra-thin nanosheets (NS) and partially exfoliated forms (PS) were rigorous studied with analytical tools to understand their structure-property-activity relationships. Remarkably, NS unveiled the highest degradation efficiency (97%) toward methylene blue dye under visible light illumination within 60 minutes followed by PS (82%) and BS (62%). EPR analysis and scavenging test predicted that super oxide radicals and singlet oxygen are responsible for enhanced and rapid degradation of MB. The intermediates and MB breakdown pathway was outlined with LC-MS studies. Experimental UV-Vis DRS analysis was correlated with DFT calculated bandgaps, enables a rare dual insight into band structure evolution. In addition, a clear quantitative bond was recognized amongst surface area, porosity and degradation efficiency. The developed photocatalysts demonstrated excellent stability over six cycles of reuse, subjected in degradation of complex water matrix with mixture of various dyes with 80.9% of mineralization emphasizes their practical relevance . Toxicity studies with plants growth (green gram seeds) suggested the growth rate (root length 16 cm; shoot length 14 cm) is similar for distilled water and dye treated water further substantiating its environmental sustainality. This research underlines the potential of morphology controlled, metal-free, scalable g-C3N4 as a strong green photocatalyst for sustainable water treatment.