Regulating the electronic properties, quantum capacitance and photocatalytic activity of Sc2CO2 based on Y doping and strain

The doping of transition metals can effectively modulate the electronic structures and enhance the photocatalytic activity of MXenes. The electronic and photocatalytic properties, as well as the quantum capacitance of Sc2CO2-Y under biaxial strain, were studied by density functional theory. Sc2CO2-Y is a direct semiconductor and keeps its semiconductor character under strain. Sc2CO2-Y under tensile strain has higher photocatalytic activity than under compressive strain. In particular, Sc2CO2-Y at 2% strain has the slowest recombination rate of electrons and holes because of the largest m(h)*/m(e)*. Sc2CO2-Y under strain is a potential cathode material. Its large potential keeps the character of cathode materials for Sc2CO2-Y under strain. Sc2CO2-Y under tensile strain has better conductivity, especially under 5% strain, due to having the largest Re (epsilon(0)). Sc2CO2-Y under strain can perform the HER, but fails to perform the OER at pH = 0, and tensile strain increases the reduction capacity of Sc2CO2-Y. Under strains from -2% to 2%, Sc2CO2-Y can perform the OER in an alkaline environment. Sc2CO2-Y is a good CO2 photocatalyst in acidic environments; the increase of pH value weakens the N-2 reducing capacity of Sc2CO2-Y under strain. Its work function, charge transfer and optical properties are also explored.