Facile preparation of nanostructured CuBi2O4 for the photoelectrochemical valorization of 4-nitrophenol to 4-aminophenol under benign conditions

• CuBi 2 O 4 was developed by drop-casting of a Cu 2+ precursor on a nanostructured BiOI. • The photocathode shows high photocurrent and a highly positive onset potential. • A faradaic efficiency of 87.4 % can be achieved at near-neutral pH over CuBi 2 O 4 . Photoelectrochemical (PEC) synthesis of value-added chemicals from organic waste has attracted significant attention, as it enables a carbon-neutral cycle. At the same time, solar energy can be stored as chemical energy. Herein, a nanostructured CuBi 2 O 4 (nanoCuBi 2 O 4 ) is demonstrated as an efficient and selective photocathode for PEC valorization of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). nanoCuBi 2 O 4 can be readily synthesized by drop-casting of a Cu 2+ precursor onto an electrodeposited BiOI template, followed by a heat treatment. The optimal condition resulted in a tetragonal CuBi 2 O 4 with a porous morphology. A photocurrent up to -0.8 mA cm −2 at 0.4 V vs the reversible hydrogen electrode (V RHE ) with a positive onset potential of 1.1 V RHE under AM 1.5 G illumination (100 mW cm −2 ) in O 2 -purged electrolyte can be achieved. Notably, the nanoCuBi 2 O 4 photocathode efficiently PEC-catalyzes the formation of 4-AP, with a faradaic efficiency of 87.4 ± 8.8 % at 0.35 V RHE without the need for any cocatalyst in a near-neutral phosphate buffer solution. This makes nanoCuBi 2 O 4 a promising material for the sustainable generation of industrial essential feedstock from harmful waste.