Cu2O/CuO heterojunction catalysts through atmospheric pressure plasma induced defect passivation

A novel route to fabricate Cu2 0/CuO heterojunction electrodes using an atmospheric pressure plasma jet (APPJ) is demonstrated. This process promotes favourable band alignment and produces nanoscale CuO surface features from Cu20 with low density of interfacial defects. This electrode can operate without any transparent current collector, showing remarkable currents and stability towards oxygen evolution reaction (OER) (6 mA cm(-2) for 2 h at pH14) as well as photocatalytic hydrogen evolution reaction (HER) activity (-1.9 mA cm(-2) for 800 s at pH7). When the electrocatalytic oxygen evolution (OER) activity was measured for Cu2O/CuO electrode deposited on FTO substrate the currents increased to similar to 40 mA cm(-2) at 0.8 V vs SCE in 1 M KOH without compensating for the electrode electrolyte surface resistance (iR correction). The composite films also exhibited a high rate towards photo degradation of Methylene Blue (MB) and phenol in the visible spectra, indicating efficient charge separation. We modelled the electronic structure of this epitaxially grown Cu2O/CuO heterojunction using density functional theory. The calculations revealed the distinctive shifts towards Fermi level of the p-band centre of O atom in Cu2O and d-band centre of Cu atom in CuO at the interface contribute towards the increased catalytic activity of the heterostructure. Another factor influencing the activity stems from the high density of excited species in the plasma introducing polar radicals at the electrode surface increasing the electrolyte coverage. This work presents the potential of APPJ functionalization to tune the surface electronic properties of copper oxide based catalysts for enhanced efficiency in OER and HER water splitting.

Automated summary

A novel method using atmospheric pressure plasma jet (APPJ) was demonstrated to fabricate Cu2 0/CuO heterojunction electrodes with favorable band alignment, producing nanoscale CuO surface features with low density of interfacial defects. The electrode showed remarkable performance in oxygen evolution reaction (OER) and photocatalytic hydrogen evolution reaction (HER). The electronic structure modeling revealed shifts in band centers at the interface, contributing to increased catalytic activity of the heterostructure. The study highlighted the potential of APPJ functionalization in tuning surface electronic properties of copper oxide catalysts for enhanced efficiency in OER and HER water splitting.