Synthesis and photocatalytic activity of quasi-one-dimensional (1-D) solid solutions Ti$_{1-x}$M$_{x}$O$_{2-2x/2}$ (M(III)= Fe(III), Ce(III), Er(III), Tb(III), Eu(III), Nd(III) and Sm(III), $0\le x\le 0.1$)

Quasi-one-dimensional (1–D) solid solutions Ti$_{1-x}$M$_{x}$O$_{2-2x/2}$ (M(III)= Fe(III), Ce(III), Er(III), Tb(III), Eu(III), Nd(III), Sm(III), $0\le x\le 0.1$) with the anatase structure have been synthesized by heating glycolate Ti$_{1-x}$M$_{x}$(OCH$_2$CH$_2$O)$_{2-x/2}$ in air at a temperature above 450$^\circ$C. A method was proposed for the production ofiron-and carbon-doped titanium dioxide with the anatase structure Ti$_{1-x}$Fe$_{x}$O$_{(2-x/2)-y}$C$_y$ and of composites basedthereon containing an excessive carbon content. It was shown that the oxide solid solutions exhibit photocatalyticactivity in the hydroquinone photooxidation reaction during irradiation in the ultraviolet spectrum. A correlationwas established between the hydroquinone oxidation rate and the concentration of the substituting ions “M” in thecatalyst. In the framework of the theory of ion-covalent binary solid solutions, a correlation was found betweenthe energy of the photocatalytic reaction and the estimated mixing enthalpy of binary solid solutions formation.