Congcong Wang,Dingke Xue,Xinyu Shen,Hua Wu,Yu Zhang,Haining Cui,William W Yu
Perovskite white light-emitting devices (WLEDs) without intercalation layers have not been achieved due to the ion exchange. Although the intercalation layers prevent ion exchange between perovskite nanocrystals (NCs), it also creates a new problem of charge imbalance and the structure becomes more complex. In this study, blue emitting ZnCdS/ZnS NCs with high quantum yield and stability are introduced to work with the yellow emission from CsPb(Br/I)3 perovskite NCs for WLEDs. The WLEDs are constituted of ITO/ZnO/PEI/ZnCdS/ZnS NCs/CsPb(Br/I)3 NCs/TCTA/MoO3/Au. This design avoids ion exchange between different perovskites NCs, and realizes white light emission by simple fabrication. As a result, we achieved the white light coordinates of (0.34, 0.34) and a correlated color temperature of 5153 K.
Studies on highly efficient heterojunction photocatalysts are regarded as an important task for H 2 production by water splitting. In this work, a novel ternary Fe 3 S 4 /ZnCdS/ZnS (FS/ZCS/ZnS) heterostructures were successfully prepared by a simple grinding method. With ZCS/ZnS nanoclusters loading on the surface of Fe 3 S 4 microflowers, photocatalytic H 2 production of ZCS/ZnS was largely improved in lactic acid (LA) solution. The H 2 evolution rate of FS/ZCS/ZnS is high up to 4.36 mmol g −1 h −1 under visible light irradiation and 8.13 mmol g −1 h −1 under full spectrum irradiation. Prolonged experiments and cycle tests showed that FS/ZCS/ZnS is stable and reusable. The formation of ternary heterostructures facilitates the separation and transfer of photogenerated charge carriers (PCCs, including photogenerated electrons and holes), leading to the activity enhancement of photocatalytic H 2 production. The strategy for the heterojunction construction can provide more perspective for the design of high-efficiency and recyclable photocatalysts for H 2 evolution.
Studies on highly efficient noble-metal-free catalysts are regarded as an important task for H2 production by water-splitting. MoS2/ZnCdS/ZnS dual heterostructures were successfully prepared with respective supernatant MoS2 colloidal solutions (called M/ZC/Z) and MoS2 precipitates (M(p)/ZC/Z). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of the M/ZC/Z sample showed that ZnS nanosheets were decorated with ZnCdS nanorods and few-layered MoS2. Then, photocatalytic hydrogen production study was performed and the results showed that the M/ZC/Z sample has a H2 evolution rate of up to 79.3 mmol g–1 h–1 under visible light irradiation with an apparent quantum efficiency of 47.9% at 420 nm with noble-metal-free catalysts, which is nearly 5 times that of the M(p)/ZC/Z sample (15.7 mmol g–1 h–1) and approximately 9 times that of the ZC/Z sample (8.98 mmol g–1 h–1). Cycle tests showed that M/ZC/Z is stable and reusable. Without sacrificial agents, the production rates for hydrogen and oxygen evolution were obtained as 3.15 and 1.55 mmol g–1 h–1, respectively. Time-resolved photoluminescence spectra revealed that the well-matched structure is effective in the separation and transfer of photogenerated electron and hole pairs, leading to the enhancement of the photocatalytic H2 production activity.
The introduction of metal complex units makes it possible to expand the functional applications of metal hydrogen-bonded organic frameworks (M-HOFs). An M-HOFs-templated strategy was developed to construct ultra-fine ZnCdS/ZnS heterojunction with high-porosity for efficient photocatalytic hydrogen production. Due to the weak and feasible hydrogen-bonding interactions, the nonmetallic units on HOFs can be quickly replaced by S 2− in aqueous solution and derived into porous sulfides without pyrolysis process. Surprisingly, the surface area of ZnCdS/ZnS heterojunction was up to 320 m 2 g −1 . The ultra-fine heterojunction with high porosity offered more surface reaction sites and shortened carrier transport distance, improving separation efficiency of photogenerated electrons and holes. The size and structure-dependent properties of ZnCdS/ZnS heterojunction exhibited excellent photocatalytic hydrogen evolution rate, which was 1.68 mmol h −1 without cocatalyst. This study provides a novel strategy for constructing ultra-fine heterojunction with high porosity and high surface area to achieve efficient H 2 evolution.
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