Amorphous Cu_2-δO as Passivation Layer for Ultra Long Stability of Copper Oxide Nanowires in Photoelectrochemical Environments

Abstract

Core-shell CuO-Cu 2 O nanowires with a surface amorphous Cu 2-δ O layer leads to high stability photocathodes for use in photoelectrochemical splitting of water. The nanowires are synthesized via carbothermal reduction of CuO nanowires at 300 • C during which a 2-3 nm conformal and amorphous Cu 2-δ O layer is formed on the nanowire surface. This Cu 2-δ O layer enhances photocurrent and improves photocorrosion stability of the nanowires. While catalyst-free, pristine CuO nanowires show a photocurrent density is 0.50 mA/cm 2 and a stability of 53% after 3.4 hours of testing at −0.50 V under AM1.5 G conditions; the catalyst-free, carbothermally reduced nanowires achieve a photocurrent density of 0.75 mA/cm 2 and an improved stability of 96% under identical test conditions. The mechanism of enhanced photocurrent and its stability is discussed in the context of extensive pre and post test nanowire characterization.

Recent progress on post-synthetic treatments of photoelectrodes for photoelectrochemical water splitting

“…125 Banerjee et al reported the formation of an amorphous Cu 2Àx O overlayer for the passivation of CuO. 138 By annealing CuO in an enclosed graphitic cylinder at 300 C for 30-120 min, the as-prepared Cu 2Àx O/Cu 2 O/CuO exhibited a photocurrent density of À0.75 mA cm À2 at 0 V vs. RHE, 1.5 times higher than that of bare CuO. The enhanced photoactivity and stability were ascribed to the formation of a type II heterojunction and the benecial electron trapping by the amorphous Cu 2Àx O overlayer.…”