Interplay between the interfacial Mo–N bonds within MoC nanodot/N-doped carbon composites for efficient photocatalytic reduction of Cr(VI) and hydrogen evolution reaction

A novel photocatalytic cocatalyst, MoC quantum dots integrated into N-doped carbon microflowers (MoC–NC), was synthesized, establishing a key Mo–N interfacial bond. The Mo–N bond's regulation was achieved by adjusting the pH of Mo-polydopamine precursor solutions. A composite photocatalyst, MoC–NC/CdS (MNS), was formed by in situ growth of nano-CdS on MoC–NC. The pH during synthesis, crucial for Mo–N bond formation, significantly influenced Cr(VI) reduction and H₂ evolution performance. The optimal MNS, created at pH 9.0, demonstrated 99.2% reduction efficiency for Cr(VI) in 20 min and H₂ evolution rate of 11.4 mmol·g^-1·h^-1 over 3 h, outperforming Pt/CdS. Mechanistic studies and density functional theory revealed MoC–NC's role in enhancing light absorption, reaction kinetics, and electron transport, attributing to its ultra-small quantum dots and abundant Mo–N bonds.