The effect of sulfur doping on the ZrTiO4 (111) surface toward the CO2RR to chemically valuable products: a density functional theory study

Abstract

Developing efficient photocatalysts for the CO₂ reduction reaction (CO₂RR) is crucial for achieving sustainable energy production and mitigating carbon emissions. This study employed density functional theory (DFT) calculations to investigate the geometric features, structural stability, electronic properties, and catalytic activity of pristine and sulfur-doped ZrTiO₄ (S-doped ZrTiO₄) (111) for the CO₂RR. Sulfur (S) dopant substitution to the oxygen site alters the electronic properties of pristine ZrTiO₄ and thus improves the visible light absorption, as shown by the band gap decrease from 3.11 to 2.53 eV. Ab initio molecular dynamics (AIMD) simulations revealed that the catalysts exhibit excellent stability up to 1273.15 K. Adsorption energy calculations suggest that S-doping enhances the interaction between CO₂ and the catalyst surface, thereby promoting more favorable reaction pathways. The potential-determining step of the CO₂RR over ZrTiO₄ and S-doped ZrTiO₄ catalysts is COOH* formation from *CO₂, with ΔG_max values of 1.48 and 1.51 eV, respectively. Based on thermodynamic and kinetic assessments, it is possible to regulate the product selectivity through S-doping modification. Such a case was linked to the competing steps during CH₂OH hydrogenation, which ultimately led to a more favorable reaction route. In the case of pristine ZrTiO₄, we can expect CH₃OH to be the major product. Meanwhile, over the S-doped ZrTiO₄ surface, the formation of CH₄ was more favorable. These findings offer fundamental insights into the role of sulfur doping in ZrTiO₄ and highlight its potential as a high-performance photocatalyst for the CO₂RR.