Construction of S-scheme p-n heterojunction between protonated g-C3N4 and α-MnS nanosphere for photocatalytic H2O2 production and in situ degradation of oxytetracycline

Photocatalytic H 2 O 2 production is a green and sustainable technology, which still exposes the issues of excessive dependence on organic electron donors and pure O 2 , and lacking effective use. It is necessary to develop more efficient and more economical photocatalysis system for H 2 O 2 production. Here, we construct a S-scheme p-n heterojunction from the p-type MnS and the n-type protonated g-C 3 N 4 (PCN) semiconductors for photocatalytic H 2 O 2 production and achieve the in situ use of H 2 O 2 for oxidative degradation of oxytetracycline (OTC). The PCN/MnS composite synthesized by a one-step method well maintains a nanosphere structure of α-MnS and load the PCN on the sphere surface to form a heterojunction with strong interaction. PCN/MnS exhibits the improved photogenerated charge separation and electron transfer efficiency. An optimal photocatalyst can produce 669.6 μM of H 2 O 2 for 6 h without using the electron donors and the pure O 2 gas. The mechanism proposed the contribution of a S-scheme p-n heterojunction forms between PCN and MnS. The electrons in conduction band (CB) of MnS are responsible for the major single-electron reduction of •O 2 - radicals and the auxiliary two-electron reduction of O 2 for H 2 O 2 production, while the holes in valence band (VB) of PCN further promote the separation of photocarriers. The photogenerated H 2 O 2 can be effectively used as an in-situ oxidant to achieve 82.2% degradation of OTC in water within 80 min. The •O 2 - radicals which originate from the in situ decomposition of H 2 O 2 over PCN/MnS mainly contribute to the OTC oxidation .