Band-gap reduction of oxides via partial hydrolysis-enhanced carbothermic reaction

In the realm of metal oxide semiconductors, reducing the bandgap often necessitates the cumbersome process of high-temperature annealing in a controlled atmosphere, such as through the carbothermal reaction. However, we unveil a graceful approach to crafting narrow-gap metal oxides by delicately governing the hydrolysis reaction of metal alkoxides. Through carefully modulated hydrolysis, carbon-based residues nestled within intermolecular confines transform into graphite, nestled beside the metal oxide. This metamorphosis enables the carbothermic reaction to transpire even in the open air at temperate conditions. Diving deeper, theoretical explorations illuminate that oxygen vacancies, introduced by partial hydrolysis, are the driving force behind the color transformation of the oxides and the enhancement of photothermal conversion efficiency. The method presented here, rooted in partial hydrolysis, paves a fresh path for the creation of black metal oxide with tailored charge transition behavior, holding great promise for solar photothermal applications. © 2023 Elsevier Ltd