Atomic Layer Deposition of TixFe2-xO3 Photoanodes and Photocurrent Response Optimization by using Response Surface Methodology

Hematite (Fe2O3) is a promising visible-light-active semiconductor material for photoelectrocatalytic applications; however, it has yet to achieve its theoretical maximum efficiency. Researchers globally are making significant efforts to enhance its performance and surpass the current efficiency limitations. Here we report the photoelectrocatalytic performance of TixFe2-xO3 films deposited by atomic layer deposition (ALD) using FeCp2 and Ti(OMe)4 as precursors. Response Surface Methodology (RSM) with a face-centered central composite design (FC-CCD) was used to model and optimize the photocurrent response of TixFe2-xO3 thin film photoanodes. Deposition parameters, including the cycle ratio of TiO2 to Fe2O3, total number of ALD cycles and deposition temperature, were selected as independent variables, while the photocurrent density (PCD) at 1.23 V and 1.70 V vs RHE was used as the response variable. Thin film depositions were carried out according to FC-CCD design matrix, followed by post-annealing at 500oC for 1 hour in air. The films were then evaluated for their photocurrent response using a photoelectrochemical cell under standard AM 1.5G illumination, 100 mW/cm2. The experimental photocurrent responses were fitted to a second-order polynomial equation, resulting in the development of a mathematical model that establishes a relationship between the deposition parameters and PCD of TixFe2-xO3 photoanode. Analysis of model parameters revealed that film thickness and dopant concentration are the most significant factors influencing the PCD of TixFe2-xO3 photoanode. This study confirms that RSM based FC-CCD can be efficiently applied for the modeling and optimization of photocurrent response of TixFe2-xO3 photoanodes.