Synthesis, characterization, and photocatalytic activity of stannum-doped MgIn2S4 microspheres

A series of Sn 2+ doped MgIn 2 S 4 photocatalysts were prepared via a facial hydrothermal method . The Sn dopants substitute the sites of Mg atom in MgIn 2 S 4 unit cell, but not alter the crystal structure, demonstrated by the results of XRD and XPS . Compared to pristine MgIn 2 S 4 , Sn-doped MgIn 2 S 4 samples exhibit significantly enhanced photocatalytic CO 2 reduction activity. With increasing the Sn dopant content, the CO 2 conversion rate first ascends, achieving the maximum rate at Sn-MgIn 2 S 4 -2 sample, and then decreases. After illumination for 4 h, the highest yield of CO and CH 4 for Sn-MgIn 2 S 4 -2 sample reaches about 3.35 and 3.33 times higher than that of pristine MgIn 2 S 4 . The theoretical results based on density functional theory calculations reveal that Sn doping in MgIn 2 S 4 tunes the band structure from the direct-transition of MgIn 2 S 4 to indirect-transition, diminishes band gap and extends the light absorption range, reduces the effective masses of holes and promotes the migration of photoinduced carriers. The experimental results also demonstrate the positive role of Sn dopant in accelerating the separation and transportation of charges, and improving CO 2 adsorption ability. This work systematically investigates and discusses the Sn 2+ doping effect in MgIn 2 S 4 on crystal structure, lattice variations, electronic band structures , CO 2 adsorption ability, and photocatalytic CO 2 reduction activity, which can provide a new hint for the fabrication of efficient photocatalyst by metal ion doping.