High performance and toxicity assessment of Ta3N5 nanotubes for photoelectrochemical water splitting.

• Ta 3 N 5 nanotubes are surface modified with a composite Co-based cocatalyst. • Co(OH) x /CoPi composite cocatalyst is electrodeposited and optimized. • Ta 3 N 5 nanotubes optimized with Co(OH) x /CoPi reached 6.3 mA/cm2 under 1 Sun. • Ta 3 N 5 nanotubes are non-toxic towards human cell line HeLa S3. In this work, Co-based cocatalysts are electrodeposited on mesoporous Ta 3 N 5 nanotubes. The electrodeposition time is varied and the optimized photoelectrode reaches a photocurrent density of 6.3 mA/cm2 at 1.23 V vs. SHE, under simulated solar illumination of 1 Sun, in 1 M NaOH. The best performing electrode, apart from the high photocurrent density, shows improved stability under intense photoelectrochemical water splitting conditions. The dual function of the cocatalyst to improve not only the photoelectrochemical performance, but also the stability, is highlighted. Moreover, we adopted a simple protocol to assess the toxicity of Co and Ta contained nanostructured materials (representing used photoelectrodes) employing the human cell line HeLa S3 as target cells. [ABSTRACT FROM AUTHOR]