Cu2O as an emerging photocathode for solar water splitting - A status review

Recently, cuprous oxide (Cu2O) based photocathodes have gained research attention for hydrogen (H-2) production through photoelectrochemical (PEC) water splitting reactions due to marginally lower synthesis cost and low energy intensity fabrication processes. Unique properties of Cu2O, such as tunable bandgap, appropriate band edge potentials with water redox levels and non-toxic nature makes it beneficial for PEC applications. Cuprite is mainly studied under visible light to facilitate enhanced H-2 gas production upon illumination. However, notoriously photocorrosion degrades the PEC performance and restricts the photoactivity of Cu2O. Moreover, because of the redox potentials lies within the band gap of Cu2O; self-photocorrosion or self-oxidation upon illumination is unavoidable. Improvement in the Cu2O photocathodes was achieved by finding elegant solutions such as forming thin heterojunction layers by atomic layer deposition (ALD) as well other methods, co-catalyst deposition, tuning crystal facets and surface modifications with different synthetic methods. In this review, we discuss the improvements in Cu2O photocathodes achieved over the years for enhanced H-2 production with recently studied photocathodes. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.