An Electrospun Porous CuBi₂O₄ Nanofiber Photocathode for Efficient Solar Water Splitting

While the CuBi₂O₄-based photocathode has emerged as an ideal candidate for photoelectrochemical water splitting, it is still far from its theoretical values due to poor charge carrier transport, poor electron-hole separation, and instability caused by self-photoelectric-corrosion with electrolytes. Establishing synthesis methods to produce a CuBi₂O₄ photocathode with sufficient cocatalyst sites would be highly beneficial for water splitting. Here, the platinum-enriched porous CuBi₂O₄ nanofiber (CuBi₂O₄/Pt) with uniform coverage and high surface area was prepared as a photocathode through an electrospinning and electrodeposition process for water splitting. The prepared photocathode material was composed of a CuBi₂O₄ nanofiber array, which has a freestanding porous structure, and the Pt nanoparticle is firmly embedded on the rough surface. The highly porous nanofiber structures allow the cocatalyst (Pt) better alignment on the surface of CuBi₂O₄, which can effectively suppress the electron-hole recombination at the electrolyte interface. The as-fabricated CuBi₂O₄ nanofiber has a tetragonal crystal structure, and its band gap was determined to be 1.8 eV. The self-supporting porous structure and electrocatalytic activity of Pt can effectively promote the separation of electron-hole pairs, thus obtaining high photocurrent density (0.21 mA/cm² at 0.6 V vs. RHE) and incident photon-to-current conversion efficiency (IPCE, 4% at 380 nm). This work shows a new view for integrating an amount of Pt nanoparticles with CuBi₂O₄ nanofibers and demonstrates the synergistic effect of cocatalysts for future solar water splitting.