Photoelectrochemical hydrogen production from water splitting using heterostructured nanowire arrays of Bi2O3/BiAl oxides as a photocathode

Abstract To date, most metal oxide-based photocathodes used in photoelectrochemical cells for water splitting contain copper cations in its composition, which can be reduced to metal Cu under cathodic bias leading to deactivation of the photoelectrode. Here, a Cu-free photocathode composed by a ternary heterostructure of Bi 2 O 3 /Al 2 Bi 24 O 39 /Al 2 Bi 48 O 75 nanowires is reported with a narrow band gap energy (1.83 eV) and suitable conduction band edge potential (−0.98 V RHE ) for water reduction to hydrogen. Photoelectrochemical measurements display that the highest photocurrent density of − 4.85 mA cm −2 at 0 V RHE under simulated sunlight is achieved by tuning the Bi:Al molar ratio of photocathode to 21:1. The photocurrent onset potential of the Bi 2 O 3 /BiAl oxides photoelectrode was estimated to be 0.57 V RHE at pH 7, which is comparable to that of silicon. Controlled potential photoelectrolysis at 0 V RHE showed a stable photocurrent of about − 2 mA cm −2 for 2 h of continuous operation. The H 2 measured at this time was 696 μmol cm −2 , which corresponds to a Faradaic efficiency of 93%. Finally, this work gives a new generation of Cu-free photocathodes and demonstrates a promising future of BiAl oxides in constructing photoelectrochemical devices for water splitting.