Generally, the loading of oxygen evolution catalyst (OEC) must be carefully controlled to an extremely thin level or the photo-generated holes will mainly charge the catalyst rather than oxidizing water. To overcome the extreme sensitivity of charge transport to catalyst thickness, we proposed the iron valence state regulating on hematite to negatively shift the surface defect state, thereby suppressing the severe OEC charging. In detail, a fluorine layer (FeO_xF_y) was inserted between Fe₂O₃ and OEC (ZIF-67) to reduce the oxidation state of iron atoms, forming a case where only part of Co(II) can be oxidized (build a rapid Co(II)/Co(III) cycle). Even in the case of thicker OEC (~10 nm), Fe₂O₃@F@ZIF-67 exhibits increased photocurrent density of 2.56 mA cm⁻² at 1.23V_RHE (~170% higher than Fe₂O₃@ZIF-67), accompanied by a rapid decrease in sensitivity to OEC loading. Above pretreatment not only relaxed the catalyst process requirements, but also provide new insights into interfacial catalysis process.

通常，必须小心地将析氧催化剂（OEC）的负载控制在极薄的水平，否则光生空穴将主要为催化剂带电而不是氧化水。为了克服电荷传输对催化剂厚度的极端敏感性，我们提出了在赤铁矿上调节铁价态以使表面缺陷态产生负向偏移的方法，从而抑制了严重的OEC充电。详细地，在Fe ₂ O ₃和OEC（ZIF-67）之间插入氟层（FeO _x F _y）以降低铁原子的氧化态，从而形成仅一部分Co（II）可以被氧化的情况（建立一个快速的Co（II）/ Co（III）循环）。即使在较厚的OEC（〜10 nm）情况下，Fe ₂ O ₃@ F @ ZIF-67在1.23V _RHE下显示出增加的2.56 mA cm ^-2的光电流密度（比Fe ₂ O ₃ @ ZIF-67高170％），同时对OEC负载的敏感性迅速降低。上述预处理不仅放松了催化剂工艺的要求，而且为界面催化工艺提供了新的见解。