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