Colloidal Quantum dots (QDs) are considered promising light harvesters for photoelectrochemical (PEC) hydrogen generation devices due to their size tunable optoelectronic properties. However, the solar-to-hydrogen (STH) efficiency and long-term stability of devices based on QDs are still relatively low, thus limiting the commercial development. These limitations are attributed to the limited absorption range of QDs, unfavourable band energy alignment and photo-oxidation. Here we propose and realize two core/multiple-shell architecture based on CdSe/CdS/ZnS QDs. The shell composition is optimized with gradient layers, forming CdSe/CdSe_xS_1-x/CdS/Zn_yCd_1-yS/ZnS core/multiple-shell structures, which reduces the surface traps and defects of QDs and simultaneously suppresses exciton recombination by providing intermediated alloyed interlayers. The PEC device based on a mesoporous TiO₂ sensitized with two types of core/multiple-shell QDs exhibited an outstanding saturated photocurrent density of 20.5 mA/cm² for alloyed core/multiple-shell QDs, under one sun illumination (AM 1.5 G, 100 mW/cm²). To our knowledge, this is comparable to the highest value reported so far for the PEC devices based on colloidal QDs. In addition, the as-prepared PEC devices exhibited excellent stability, maintaining ~93.4% of the initial photocurrent density after 2-hour continuous illumination (100 mW/cm²). This work provides an efficient approach for improving the performance of PEC devices through QDs structure engineering.

胶体量子点 (QD) 因其尺寸可调的光电特性而被认为是用于光电化学 (PEC) 制氢装置的有前途的光收集器。然而，基于量子点的器件的太阳能制氢（STH）效率和长期稳定性仍然相对较低，从而限制了商业发展。这些限制归因于量子点的有限吸收范围、不利的带能排列和光氧化。在这里，我们提出并实现了基于 CdSe/CdS/ZnS 量子点的两核/多壳架构。壳层成分通过梯度层优化，形成 CdSe/CdSe _x S _1-x /CdS/Zn _y Cd _1-yS/ZnS 核/多壳结构，可减少 QD 的表面陷阱和缺陷，同时通过提供中间合金夹层来抑制激子复合。基于介孔 TiO _2与^两种 类型的核/多壳 QD 敏化的 PEC 器件在一次阳光照射下（AM 1.5 G， 100毫瓦/厘米² )。据我们所知，这与迄今为止报告的基于胶体量子点的 PEC 设备的最高值相当。此外，所制备的 PEC 器件表现出优异的稳定性，在 2 小时连续光照后（100   毫瓦/厘米² )。这项工作为通过量子点结构工程提高 PEC 器件的性能提供了一种有效的方法。