Influence of Film Thickness on Screen‐Printed BiFeO 3 Photoelectrodes for Nitrogen Reduction Reaction

ABSTRACT In the last years, perovskites structures have been explored for their ability to photo‐electrochemically store hydrogen in the form of ammonia. Various types of perovskites, ranging from halide inorganic perovskites to oxidic systems with single or double perovskite structures, have been investigated for this purpose. In this study, a simple and low‐cost single oxide perovskite, specifically BiFeO 3 (BFO), was synthesized via a sol‐gel method and the related photo‐electrodes were optimized in terms of film thickness and tested for nitrogen reduction reaction (N 2 RR). The resulting BFO powder was comprehensively characterized from the structural, optical, and morphological points of view. Screen‐printed photoelectrodes with an optical band gap of 2.17±0.05 eV were prepared and the influence of the film thicknesses on the photoelectrochemical properties was assessed. From Mott‐Schottky analyses, all systems were thermodynamically suitable to drive N 2 RR at pH 7 while thicker films were able to produce, under illumination, 22 µA cm −2 at ‐0.6 V versus NHE due to a reduced charge transfer resistance. A Faradic Efficiency close to 90 ± 9% for NH 3 was obtained at ‐0.4 V versus NHE with a yield of 9 µg h −1 cm −2 without producing hydrogen, highlighting the importance of bismuth and iron atoms on the nitrogen selectivity.