Construction of Advanced S-Scheme Heterojunction Interface Composites of Bimetallic Phosphate MnMgPO4 with C3N4 Surface with Remarkable Performance in Photocatalytic Hydrogen Production and Pollutant Degradation

Novel S-scheme heterojunction interface composite (MnMgPO4@C3N4) of bimetallic phosphate MnMgPO4 and C3N4 with different proportions was successfully constructed in this work. The nanosheet surface structure and the integration interface of two materials endowed the composite heterojunctions with superior visible light absorption and improved photogenerated carrier transfer, boosting the photocatalytic hydrogen production and degradation performance. The interface composite (5C5MMP) with the optimal mass ratio (MnMgPO4/C3N4 = 5/5) achieved the strongest photocatalytic potency. The hydrogen evolution rate was about 3.595 mmol<middle dot>g-1<middle dot>h-1, and the pollutants of methylene blue (MB), oxytetracycline (OTC), and tetracycline (TE) were almost entirely degraded within 40 min. The degradation rates were approximately 97.1% (MB), 95.4% (OTC), and 99.7% (TE). Notably, the heterojunction interface composite displayed exceptional photocatalytic stability and structural durability. The photocatalytic mechanism revealed that the 5C5MMP heterojunction interface exhibited the strongest photocurrent response, the least electron transfer resistance, and the lowest carrier recombination rate, resulting in exceptional photocatalytic performance. Furthermore, both C3N4 and MgMnPO4 were identified as n-type semiconductors. The optimized band structure of the composite photocatalyst interface and the enhanced charge carrier separation enabled the 5C5MMP photocatalytic system to generate more reactive photogenerated electrons for reduction and holes for oxidation, significantly accelerating the photocatalytic hydrogen production and pollutant degradation. By proposing an S-scheme heterojunction interface composite, this research offers an innovative strategy for designing efficient composite photocatalysts and underscores the feasibility of using bimetallic phosphate composites to enhance hydrogen production and pollutant removal.