Phosphorylated g-CN/sulfur self-doped g-CN homojunction carboxymethyl cellulose beads: An efficient photocatalyst for HO production.

The development of highly reusable, affordable, and durable photocatalysts for the production of hydrogen peroxide (HO) remained a challenge. In this study, a homojunction photocatalyst (SPGCN) is constructed between phosphorylated g-CN (PCN) and sulfur self-doped g-CN (SCN) using a simple wet impregnation method. Later, the obtained SPGCN homojunction is transformed into hydrogel beads using carboxymethyl cellulose via an effective cross-linking strategy (SPGCN/CMC). The photocatalytic beads displayed a phenomenal HO production of 3.5 mM under visible light illumination for 60 min. The SPGCN/CMC hydrogel beads showed a maximum reusability of 10 cycles with a decline of 1.5 mM HO production. The improved photocatalytic efficiency is indicated by strengthened utilization of visible light via tuning of the band gap, suppressed recombination of electron-hole pairs, and higher separation efficiency through the effective construction of Z-scheme between the phosphorylated carbon nitride and the sulfur-self-doped carbon nitride present in the SPGCN/CMC beads. The mechanistic studies affirmed the dominant role of superoxide radicals in HO production. The photocatalytic HO production followed a highly selective two-electron reduction reaction. Overall, this study highlights the efficient engineering of carbon nitride-based materials towards artificial photosynthesis.