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Strongly coupled CdS/graphene quantum dots nanohybrids for highly efficient photocatalytic hydrogen evolution: Unraveling the essential roles of graphene quantum dots

机译：用于高效光催化氢气进化的强耦合CDS /石墨烯量子点纳米组织：揭开石墨烯量子点的基本作用

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It have been recognized that the coupling of graphene quantum dots (GQDs) with semiconductor photocatalysts endow the resulting nanocomposites with enhanced photocatalytic performances, however, the essential roles of GQDs have not been clearly revealed yet. Herein, we report that a high efficiency of the photocatalytic H2 evolution was achieved using strongly coupled nanohybrids of CdS with GQDs (CdS/GQDs) as visible-light-driven photocatalysts. CdS/GQDs nanohybrids were synthesized by a facile hydrothermal method in which the crystallization of CdS precursor and coupling of GQDs could be accomplished in one-step. GQDs are firmly decorated on the surface of CdS nanoparticles, forming “dot-on-particle” heterodimer structures. GQDs have no significant influence on the crystallite structure of CdS but render the nanohybrids with strong light absorption at the wavelength beyond the band edge of CdS. Under visible light irradiation (≥420nm), CdS/GQDs nanohybrids reach the highest H2 production rate of 95.4μmol·h−1, about 2.7 times higher than that of pure CdS nanoparticles, at GQDs content of 1.0wt %, and the apparent quantum efficiency (AQE) was determined to be 4.2% at 420nm. Incident light-wavelength dependent experiments reveal that the light absorption of CdS dominated the performance of nanohybrids, and the excess light absorption coming from GQDs hardly contributes to the observed higher activity. Photocurrent response, steady-state and time-resolved PL, and EIS measurements suggest that the high activity of CdS/GQDs is attributed predominantly to the graphene-like nature of GQDs, which can act as an efficient electron acceptor to induce an efficient charge separation. This work clearly reveals that GQDs mainly played a role of electron acceptor instead of a photosensitizer in enhancing the photocatalytic H2 evolution performances of CdS/GQDs nanohybrids, which offers a new insight to understand the essential roles of GQDs in semiconductor/GQDs nanohybrids for efficient solar energy conversion applications.
机译：已经认识到，石墨烯量子点（GQDS）与半导体光催化剂的偶联赋予所得纳米复合材料具有增强的光催化性能，然而，GQD的基本作用尚未清楚地揭示。在此，我们报告说，使用具有GQDS（CDS / GQDS）的CDS的强偶联的CD纳米嗜含量为可见光的光催化剂，实现了光催化H2进化的高效率。通过容易水热法合成CdS / GQDS纳米组织，其中Cds前体的结晶和GQDS的偶联可以在一步中完成。 GQDS牢固地装饰在CDS纳米颗粒的表面上，形成“点粒子”异二聚体结构。 GQD对CD的微晶结构没有显着影响，但在波长的波长下具有强光吸收的纳米冬小麦的影响。在可见光照射（≥420nm）下，Cds / gqds纳米冬次含量达到95.4μmol·h-1的最高H2生产率，比纯CDS纳米粒子高约2.7倍，GQDS含量为1.0wt％，表观量子效率（AQE）确定为420nm的4.2％。入射光波长依赖性实验表明，CD的光吸收占据纳米冬小的性能，来自GQD的过量光吸收几乎没有导致观察到的更高的活性。光电流响应，稳态和时间分辨的PL和EIS测量表明CDS / GQD的高活性主要归因于GQD的石墨烯样本，其可以充当诱导有效电荷分离的有效电子受体。这项工作清楚地表明，GQD主要发挥了电子受体的作用，而不是增强CDS / GQD纳米布麦的光催化H2演化性能，这提供了一种新的洞察，可以了解GQD在高效太阳能的半导体/ GQD纳米油状物中的基本作用能量转换应用。

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