Hierarchical Bi2WO6 embedded nanoporous thin films as photoanodes for PEC water splitting

Abstract

To reach climate goals and reduce global warming, a critical challenge is to decarbonize the energy network and switch to renewable energy sources. However, the intermittent nature of renewable energy raises the need for sustainable methods to store large amounts of renewable energy. Photoelectrochemical (PEC) water splitting offers a promising solution to convert and store renewable energy as hydrogen. This work focuses on a nanoporous Bi2WO6 thin film as a stable, large bandgap protective photoanode for PEC water splitting. We synthesized Bi2WO6 microspheres and nanoflakes using a well-established hydrothermal method and produced nanoporous Bi2WO6 thin films using a citrato-complex aqueous solution-gel method. These films were modified by embedding them with Bi2WO6 microspheres or nanoflakes. Photoelectrochemical characterization shows comparable performance for all thin film types, with an onset potential of 0.2 V vs. RHE, a current density of 0.31 mA/cm2 at 1.23 V vs. RHE under 1.5 sun illumination, and stable operation for 1 hour. This performance is competitive with or superior to existing literature for nanoporous Bi2WO6 thin films. This paper demonstrates that the citratocomplex aqueous solution-gel method is a viable approach for fabricating high-quality nanoporous Bi2WO6 thin films for PEC applications, enhancing particle integration and surface attachment.