Engineered controlled on the synthesis of bismuth-molybdenum oxide semiconductors tailors photoelectrocatalytic activity

Abstract

The engineered fabrication of Bi₂MoO₆ thin-films enables controlled modification of photoelectrocatalytic responses based on the synthesis method. Using a modified Pechini auto-combustion method, which involves the formation of stable chelates between mixed metal ions and citric acid, the photoelectrochemical performance of Bi₂MoO₆ can be tuned by varying the synthesis components. This study elucidates the impacts of HNO₃, NH₃, and Bi³⁺ concentrations during the manufacturing of Bi₂MoO₆ thin layers. The concentration of HNO₃ was critical for the formation of a high-purity crystallographic phase. Adding NH₃ enhanced photoelectrochemical responses due to its thermal effect during combustion, resulting from crosslinking between metal-citrate complexes. Additionally, the photocurrent response under applied potential and light irradiation (λ = 365 nm) could be tuned by adjusting the stoichiometry between Bi³⁺ and Mo⁶⁺. The optimal Bi³⁺:Mo⁶⁺ ratio resulted in the maximum photocurrent of 0.65 mA cm^-2 at 0.61 V vs Ag/AgCl (1.23 V vs RHE) and lowest charge transfer resistance value of 0.8 kΩ when evaluated in the presence of hole-scavenger species. This study provides an understanding into the role of each synthesis component and highlights the importance of optimizing synthesis procedures to achieve higher photoelectrochemical performance in thin-film catalysts.