Copper oxides are considered to be very promising materials for promoting a hydrogen evolution reaction (HER). However, some CuO features, such as the recombination of charge carriers, electron diffusion length, and the chemical stability need to be improved. In this work, NiO_x was studied as co-catalyst to FTO/CuO, and the films were physically characterised by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The photo-electrochemical activity and stability toward the HER were evaluated by depositing films on fluorine-tin doped oxide (FTO) substrate. Although, the CuO (− 3.61 eV) and NiO_x (− 1.13 eV) conduction band positions, estimated by UV-Vis diffuse reflectance and the Mott–Schottky measurements, did not allow electronic transfer from CuO to NiO_x, the formation of a thin layer of NiO_x on CuO was beneficial for the activity of this material. The best CuO/NiO_x film exhibited a photocurrent density of − 1.02 mA cm⁻² at 0 V vs. RHE, which was higher than that for CuO (− 0.92 mA cm⁻²). A mechanism of electron transfer between CuO and NiO_x is proposed. The absorption of visible light by CuO leads to the generation of electron-hole pair. Part of the photogenerated electrons are trapped by the NiOOH present in the NiO_x layer, as demonstrated by XPS. The oxy-hydroxide is reduced to metallic Ni, and this species acts as a catalyst for the hydrogen evolution reaction. Due to the increase in interfacial pH caused by the evolution reaction of H₂, the formed metallic Ni can be regenerated to NiO_x.

氧化铜被认为是促进氢释放反应（HER）的非常有前途的材料。然而，一些CuO特征，例如电荷载流子的复合，电子扩散长度和化学稳定性需要改善。在这项工作中，研究了NiO _x作为FTO / CuO的助催化剂，并通过X射线衍射（XRD），X射线光电子能谱（XPS）和扫描电子显微镜（SEM）对薄膜进行了物理表征。通过在氟锡掺杂的氧化物（FTO）衬底上沉积膜来评估其对HER的光电化学活性和稳定性。虽然，CuO（-3.61 eV）和NiO _x通过UV-Vis漫反射率和Mott-Schottky测量估计的（-1.13 eV）导带位置不允许电子从CuO转移到NiO _x，在CuO上形成一层薄的NiO _x有利于活性这种材料。最佳的CuO / NiO _x膜在0 V相对于RHE的光电流密度为-1.02 mA cm ^-2，高于CuO（-0.92 mA cm ^-2）。提出了CuO和NiO _x之间电子转移的机理。CuO对可见光的吸收导致电子-空穴对的产生。部分光生电子被NiO _x中存在的NiOOH捕获XPS演示了这一层。羟基氧化物被还原为金属Ni，并且该物种充当氢释放反应的催化剂。由于H ₂的析出反应引起的界面pH的增加，形成的金属Ni可以再生为NiO _x。