Facile solution combustion synthesis of mesoporous HfTiO4 as novel photoanode material with enhanced visible-light response

Abstract

In this research endeavor, we report the successful synthesis of mesoporous and single-phase nanopowders of orthorhombic hafnium titanate, HfTiO4, using a facile solution combustion approach. The direct synthesis yielded an X-ray amorphous product, which was found to crystallize completely into single-phase HfTiO4 upon annealing at 800 °C for 1 h, marking the first successful synthesis of this material via this method. The synthesized HfTiO4 nanopowders were thoroughly characterized using various techniques. Structural analyses conducted through powder X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy confirmed the formation of pure orthorhombic HfTiO4 nanocrystals, exhibiting an average size of 24.6 nm. Moreover, the scanning electron microscopy (SEM) morphological study and adsorption-structural analysis of the HfTiO4 nanopowder revealed a well-developed mesoporous structure with a specific surface area of 17 m2/g and an average pore size of 15 nm. The band gap of the synthesized HfTiO4 was determined to be 3.47 eV, designating it as a potential photoanode material. Photocatalytic applications were evaluated through photoelectrochemical tests, which showcased a high photoresponse in both the UV (365 nm) and visible (450 nm) regions of the spectrum. Importantly, the photoresponse under visible light surpassed that of commercial TiO2 (Sigma-Aldrich), signifying its potential as an efficient photoanode material.