Template-free synthesis of Mn²⁺ doped hierarchical CuS yolk–shell microspheres for photocatalytic reduction of Cr(vi)

Abstract

Yolk-shell structures have been widely used in catalysis and energy storage in recent years because they improve the efficiency of charge utilization by enhancing light scattering and creating more active...

Electronic Properties of Transition and Alkaline Earth Metal Doped CuS: A DFT Study

“…Although Mn doping was not studied in this work, the general finding that transition metal doping tends to give relatively high electron masses is consistent with previous work showing that Mn ions in CuS can modify the charge carrier dynamics and decrease recombination by trapping electrons [42] …”

“…Although Mn doping was not studied in this work, the general finding that transition metal doping tends to give relatively high electron masses is consistent with previous work showing that Mn ions in CuS can modify the charge carrier dynamics and decrease recombination by trapping electrons. [42] In the [001] direction, hole mobility increases compared with undoped CuS for all dopants except Mg and Ca while hole mobility in the [100] direction is quite similar for all dopants; this similarity of all hole masses in the [100] direction may be due to the valence band states being formed predominantly by the same atoms for all the dopants. In general, the alkaline earth dopants tend to increase hole mass and decrease electron mass compared with undoped CuS, while the transition metal dopants tend to have both electron and hole masses decreased in the [001] direction and increased in the [100] direction.…”

“…The reduction in the band gap of CuS due to doping with Fe is consistent with a previous experimental study, [41] as well as reports of the effects of other transition metal dopants. [40,42] For Cr-doped CuS, there is also a significant contribution from dopant states at the VB maximum, which is not seen for the other dopants.…”

“…For example, in a study of M cation (M=Co 2+ , Ho 2+ ) doped CuS, [40] both dopants were found to cause an expansion of the CuS crystal structure (i. e., increased volume of the unit cell) and a red shift in the band gap, resulting in an enhancement of visible‐light absorption and photocatalytic activity compared to pure CuS. Similarly, doping CuS with Fe has been found to decrease the band gap from 2.47 eV to 1.98 eV and increase the optical absorption coefficient from 1.15×10 5 cm −1 to 1.71×10 5 cm −1 , [41] while Mn doping has been found to not only narrow the band gap (to 1.35 eV, compared to 1.58 eV for undoped CuS) but also reduce the recombination rate due to the Mn ions serving as trapping sites for photogenerated electrons [42] . Ni doping of CuS was found to decrease the charge transfer resistance and change the surface atomic environments and electronic structure, as well as introduce defects, resulting in an improvement in the oxygen evolution reaction (OER) activity of CuS [43] .…”

“…Similarly, doping CuS with Fe has been found to decrease the band gap from 2.47 eV to 1.98 eV and increase the optical absorption coefficient from 1.15×10 5 cm À 1 to 1.71×10 5 cm À 1 , [41] while Mn doping has been found to not only narrow the band gap (to 1.35 eV, compared to 1.58 eV for undoped CuS) but also reduce the recombination rate due to the Mn ions serving as trapping sites for photogenerated electrons. [42] Ni doping of CuS was found to decrease the charge transfer resistance and change the surface atomic environments and electronic structure, as well as introduce defects, resulting in an improvement in the oxygen evolution reaction (OER) activity of CuS. [43] Khalili and Dehghani [44] showed that using a doped CuS counter-electrode in a quantum dot-sensitized solar cell (with a TiO 2 photoanode) can improve the power conversion efficiency (PCE).…”