Providing sufficient driving force for charge separation is a critical requirement in photocatalytic H₂ evolution (PHE), but it remains challenging to precisely adjust the charge separation. Herein, we address this challenge by constructing a NH₂-UiO-66/CoFe₂O₄/CdIn₂S₄ (NU6/CFO/CIS) double p-n junction with double internal electric fields. Compared with p-n junction with single internal electric field, double p-n junction enables photocatalysts with dual carrier transfer channels, faster carrier separation rate and stronger redox capacity. Additionally, PHE rate is related to the mass of photocatalyst used and a different photocatalyst weight may lead to a different PHE rate. When an excessive amount of photocatalyst is used, most of the photocatalyst cannot adsorb sufficient light and the photocatalytic rate is lower when normalized by the unit photocatalyst mass. Therefore, the effect of photocatalyst mass on PHE rate and apparent quantum yield are investigated in depth. The 25% NU6/2% CFO/CIS double p-n junction exhibits comparable PHE activity, its activity is about 13.5 times and 2.5 times higher than that of CIS and 2% CFO/CIS single p-n junction. In-situ XPS, density functional theory calculations, and Pt ion probe method are used to confirm where the photogenerated charges go and where they react, which is very in accordance with the “double p-n junction with double internal electric fields” mechanism. This work not only provides some ideas for the design of high-efficiency photocatalysts, but also offers a reference for the photocatalytic performance evaluation system.

为电荷分离提供足够的驱动力是光催化析氢 (PHE) 的关键要求_，但精确调整电荷分离仍然具有挑战性。在此，我们通过构建具有双内电场的 NH ₂ -UiO-66/CoFe ₂ O ₄ /CdIn ₂ S ₄ (NU6/CFO/CIS) 双pn结来应对这一挑战。与单内电场的pn结相比，双pn结结使光催化剂具有双载流子传输通道、更快的载流子分离速率和更强的氧化还原能力。此外，PHE 速率与所用光催化剂的质量有关，不同的光催化剂重量可能导致不同的 PHE 速率。当使用过量的光催化剂时，大部分光催化剂不能吸收足够的光，并且当以单位光催化剂质量归一化时，光催化速率较低。因此，深入研究了光催化剂质量对PHE速率和表观量子产率的影响。25% NU6/2% CFO/CIS双pn结表现出相当的PHE活性，其活性约为CIS和2% CFO/CIS单pn的13.5倍和2.5倍交界处。采用原位XPS、密度泛函理论计算和Pt离子探针法确定光生电荷的去向和反应位置，非常符合“双pn结双内电场”机理。该工作不仅为高效光催化剂的设计提供了一些思路，也为光催化性能评价体系提供了参考。