Recently, colloidal semiconductor quantum dots (QDs) have shown great promise as photocatalysts for the production of chemical fuels by sunlight. Here, the efficiency of photocatalytic hydrogen (H₂) production for integrated systems of large diameter (4.4 nm) CdSe QDs as light harvesting nanoparticles with varying concentrations of nickel–dihydrolipoic acid (Ni–DHLA) small molecule catalysts is measured. While exhibiting excellent robustness and longevity, the efficiency of H₂ production for equimolar catalyst and QDs is relatively poor. However, the efficiency is found to increase substantially with increasing Ni–DHLA/QD molar ratios. Surprisingly, this high activity is only observed with the use of 3-mercaptopropionic acid (MPA) ligands, while CdSe QDs capped with dihydrolipoic acid (DHLA) exhibit poor performance in comparison, indicating that the QD capping ligand has a substantial impact on the catalytic performance. Ultrafast transient absorption spectroscopic measurements of the electron transfer (ET) dynamics show fast ET to the catalyst. Importantly, an increase in ET efficiency is observed as the catalyst concentration is increased. Together, these results suggest that for these large QDs, tailoring the QD surface environment for facile ET and increasing catalyst concentrations increases the probability of ET from QDs to Ni–DHLA, overcoming the relatively small driving force for ET and decreased surface electron density for large diameter QDs.

中文翻译：

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CdSe量子点的活性和高效光催化H _2产生的回收

近来，胶体半导体量子点（QDs）作为光催化剂用于阳光生产化学燃料已显示出巨大的希望。在这里，测量了大直径（4.4 nm）CdSe QDs集成系统的光催化氢（H ₂）的生产效率，这些系统是具有不同浓度的镍-二氢硫辛酸（Ni-DHLA）小分子催化剂的光收集纳米颗粒。H ₂表现出出色的鲁棒性和寿命，同时具有很高的效率等摩尔催化剂和量子点的生产相对较差。但是，发现效率随着Ni-DHLA / QD摩尔比的增加而大大提高。出乎意料的是，仅在使用3-巯基丙酸（MPA）配体时才观察到这种高活性，而用二氢硫辛酸（DHLA）封端的CdSe QD表现出较差的性能，表明QD封端配体对催化表现。电子转移（ET）动力学的超快速瞬态吸收光谱测量显示出对催化剂的快速ET。重要地，随着催化剂浓度的增加，观察到ET效率的增加。总之，这些结果表明，对于这些大型QD，