Morphology-dependent activation of hydrogen peroxide with Cu2O for tetracycline hydrochloride degradation in bicarbonate aqueous solution

The design of efficient heterogeneous catalysts in bicarbonate-activated hydrogen peroxide systems (BAP) is a hot topic in wastewater treatment. In this work, Cu 2 O nanoparticles with different morphologies including cubic shape (c-Cu 2 O), octahedron shape (o-Cu 2 O) and spherical shape (s-Cu 2 O), were applied in BAP for the first time to degrade tetracycline hydrochloride (TC). Compared with Cu 2+ ions and CuO, TC degradation was boosted in the presence of Cu 2 O in the BAP system, with the degradation rate following the order c-Cu 2 O > o-Cu 2 O > s-Cu 2 O. The morphology-dependent effects could be linearly correlated with the ratio of surface oxygen species (O S ), but not with the surface area or Cu(I) ratio. The c-Cu 2 O catalyst with exposure of (100) facets contained 76.6% O S as the active site for H 2 O 2 adsorption and activation, while the value was much lower for o-Cu 2 O and s-Cu 2 O with dominant (111) facets. The presence of HCO 3 − enhanced the interactions among Cu 2 O, H 2 O 2 and TC, leading to facile oxidation of Cu(I) to Cu(II) by H 2 O 2 , and the formation of various reactive species such as hydroxyl radicals and Cu(III) contributed to TC degradation. This work provides a new method for enhancing H 2 O 2 activation with heterogeneous catalysts by crystal facet engineering.