Cutting-Edge PCN-ZnO\nNanocomposites with Experimental\nand DFT Insights into Enhanced Hydrogen Evolution Reaction

Polymeric carbon nitride (PCN) and PCN-ZnO nanocomposites\nare promising\ncandidates for catalysis, particularly for hydrogen evolution reactions\n(HER). However, their catalytic efficiency requires enhancement to\nfully realize their potential. This study aims to improve the HER\nperformance of PCN by synthesizing PCN-ZnO nanocomposites using melamine\nas a precursor. Two synthesis methods were employed: thermal condensation\n(Method 1) and liquid exfoliation (Method 2). Method 1 resulted in\na composite with a 2.44 eV energy gap and reduced particle size, with\nsignificantly enhanced performance as a bifunctional electrocatalyst\nfor simultaneous hydrogen and oxygen production. In contrast, Method\n2 produced a nanocomposite with an enhanced surface area and a minor\nalteration in the band gap. In alkaline electrolytes, the PCN-ZnO<sub>0.4</sub> nanocomposite synthesized with Method 1 exhibited high\nHER performance with an overpotential of 281 mV, outperforming pristine\nPCN (382 mV) and ZnO (302 mV), along with improved oxygen evolution\nreaction (OER) activity. Further analysis in a two-electrode alkaline\nelectrolyzer using PCN-ZnO<sub>0.4</sub> nanocomposite as both the\nanode and cathode demonstrated its promise as a bifunctional electrocatalyst.\nDensity functional theory (DFT) calculations explained the enhanced\ncatalytic activity of the PCN-ZnO nanocomposite, confirming that hydrogen\nevolution occurs through the Heyrovsky process, consistent with experimental\nresults. Notably, the solar-to-hydrogen (STH) efficiency of the PCN-ZnO\nnanocomposite was four times greater, at 21.7% compared to 5.2% for\nthe PCN monolayer, underscoring its potential for efficient solar-driven\nhydrogen production. This work paves the way for future advancements\nin the design of high-performance electrocatalysts for sustainable\nenergy applications.