Boosting the photocatalytic performance of Cu₂O for hydrogen generation by Au nanostructures and rGO nanosheets

As a narrow band-gap semiconductor, cuprous oxide (Cu₂O) has a relatively high conduction band that can exhibit high driving force for the photocatalytic generation of hydrogen under visible light. Besides, its adjustable morphologies and abundant source also make it possible to be employed as a theoretically optimal photocatalyst. However, the low charge migration and poor stability commonly limit its practical application, and various strategies have been explored in previous studies. In this study, we have novelly utilized Au nanorod (NR) and nanobipyramid (NBP) nanocrystallites as well as rGO nanosheets to boost the photocatalytic activity of Cu₂O over hydrogen generation. The ternary rGO wrapped Au@Cu₂O with a yolk-shelled structure (y-Au@Cu₂O/rGO) was synthesized by a handy and controllable method. When excited by solar light (λ > 400 nm), it was found that the H₂ yields of Cu₂O/rGO, y-Au nanoparticle@Cu₂O/rGO, y-Au NR@Cu₂O/rGO, and y-Au NBP@Cu₂O/rGO were increased in the order of 248, 702, 1582 and 1894 μmol g^-1 in 4 h. The outstanding photocatalytic performances of y-Au NR@Cu₂O/rGO and y-Au NBP@Cu₂O/rGO could be attributed to the combination function of quick electron transfer of rGO and abundant near-infrared-light-driven hot carriers on Au NRs and NBPs that could inject into Cu₂O and then a quick transfer to rGO to participate in H₂ reduction. Besides the above results, it was also found that Cu₂O maintained good stability after several cycling photocatalysis tests, which could be ascribed to the migration of holes from Cu₂O to Au that prevented the photooxidation of Cu₂O. This study may give a guide to fabricating controllable and effective photocatalysts based on plasmonic metals, semiconductors, or two-dimensional nanosheets, which possess full-solar-light-driven photocatalytic activities in the future.