Insights into the photoactivity of iron modified bismuth titanate (Fe_BTO) nanoparticles

Abstract The photoactivity of a bandgap engineered composite oxide nanostructure − BECON − comprising of Bi, Ti, and O as the building blocks and Fe as an earth-abundant additive (Fe-BTO) has been examined in the presence of UV–vis illumination of water-methanol system. The performance of the Fe-BTO was investigated by examining the effects of Fe-BTO loading, light intensity, methanol concentration, and Fe-BTO stability upon repeated use. Among the parameters evaluated, the photoactivity using 150 mg of catalyst was determined most effective with a methanol concentration of 20 M. In additional insights, all of the time resolved experiments indicated the existence of a methanol concentration dependent 2-zone activity region: zone 1- slow photoactivity and zone 2- accelerated photoactivity. The presence of the 2-zone region is attributed to the intermediates formed during the methanol oxidation. The formation of the intermediate formic acid, which is thermodynamically favored, is identified as one of the key stages in the reaction. Further, repeated use of the Fe-BTO leads to over a 70% loss in the photoactivity. This may be attributed to (i) the formation of surface-functional groups and/or (ii) intrinsic change in the Fe-BTO upon irradiation.