Effective photoelectrocatalytic reduction of CO2 to formic acid using controllably annealed TiO2 nanoparticles derived from porous structured Ti foil

The rate of global warming and unfavorable climate changes caused by the drastic upsurge of carbon dioxide (CO2) emission has necessitated the development of approaches to limit the significantly high concentration of CO2 in the atmosphere. The photoelectrochemical reduction of CO2 results in a reduction of the energy required to transform this greenhouse gas into valuable end products. In this study, we fabricated cost-effective and novel 3D nanoporous structured (3DNS) TiO2 nanoparticles (T-NPs) on the surface of a thin titanium foil (T-foil) by chemical treatment with hydrogen peroxide (H2O2) followed by calcination at high temperatures in the range of 400-800 degrees C. The as-proposed samples were analyzed by several characterizations such as XRD, XPS, TEM, and Raman spectroscopy. At 600 degrees C, the anatase-dominated mixed phases of calcinated T-foil (TO600) were seen, and a maximum photocurrent density of 71.5 mu A/cm(2) was obtained, in comparison to the T-foils treated at other temperatures (TO400, TO500, TO700, and TO800). Because of the better photocurrent density, TO600 was selected as the photocathode material for photoelectrochemical CO2 reduction performed with or without the presence of solar light. The lowest CO2 reduction onset potential (-1.191 V) was observed on the TO600 sample in the presence of light with Ag/AgCl as the reference electrode. H-1 NMR analysis of the product solution revealed the formation of formic acid as the major product of the CO2 reduction reaction after the chronoamperometric electrolysis was performed for more than 25 h. The maximum faradaic efficiency (64%) and formic acid yield (165 mu mol cm(-2) h(-1)) were obtained at an applied potential of - 1.3 V (vs. Ag/AgCl reference electrode) for TO600.

Automated summary

In this study, cost-effective and novel 3D nanoporous structured TiO2 nanoparticles were fabricated for photoelectrochemical reduction of CO2. The samples prepared at 600 degrees C exhibited the highest photocurrent density and the lowest CO2 reduction onset potential.