Double quantum dots decorated 3D graphene flowers for highly efficient photoelectrocatalytic hydrogen production

Photoelectrocatalysis (PEC) has been demonstrated as a promising technique for hydrogen production. However, the high over-potential and high recombination rate of photo-induced electron-hole pairs lead to poor hydrogen production efficiency. In order to overcome these problems, TiO2 and Au dual quantum dots (QDs) on three-dimensional graphene flowers (Au@TiO2@3DGFs) was synthesized by an electro-deposition strategy. The combination of Au and TiO2 modulates the band gap of TiO2, shifts the absorption to visible lights and improves the utilization efficiency of solar light. Simultaneously, the size-quantization TiO2 on 3DGFs not only achieves a larger specific surface area over conventional nanomaterials, but also promotes the separation of the photo-induced electron-hole pairs. Besides, the 3DGFs as a scaffold for QDs can provide more active sites and stable structure. Thus, the newly-developed Au@TiO2@3DGFs composite exhibited an impressive PEC activity and excellent durability. Under −240 mV potential (vs. RHE), the photoelectric current density involved visible light illumination (100 mW cm−2) reached 90 mA cm−2, which was about 3.6 times of the natural current density (without light, only 25 mA cm−2). It worth noting that the photoelectric current density did not degrade and even increased to 95 mA cm−2 over 90 h irradiation, indicating an amazing chemical stability.