Photoelectrochemical water splitting and CO₂ reduction provide an attractive route to produce solar fuels while reducing the level of CO₂ emissions. Metal halide perovskites (MHPs) have been extensively studied for this purpose in recent years due to their suitable optoelectronic properties. In this review, we survey the recent achievements in the field. After a brief introduction to photoelectrochemical (PEC) processes, we discussed the properties, synthesis, and application of MHPs in this context. We also survey the state-of-the-art findings regarding significant achievements in performance, and developments in addressing the major challenges of toxicity and instability toward water. Efforts have been made to replace the toxic Pb with less toxic materials like Sn, Ge, Sb, and Bi. The stability toward water has been also improved by using various methods such as compositional engineering, 2D/3D perovskite structures, surface passivation, the use of protective layers, and encapsulation. In the last part, considering the experience gained in photovoltaic applications, we provided our perspective for the future challenges and opportunities. We place special emphasis on the improvement of stability as the major challenge and the potential contribution of machine learning to identify the most suitable formulation for halide perovskites with desired properties.

The CuO@CuFe₂O₄ core–shell structure represents a new family of photocatalysts that can be used as photoelectrodes that are able to produce hydrogen under a broad spectrum of visible light. Herein, we report a novel approach for the production of this active film by the thermal conversion of CuFe Prussian Blue Analogues. The outstanding photoelectrochemical properties of the photocathodes of CuO@CuFe₂O₄ were studied with the use of combinatory photo-electrochemical instrumental techniques which proved that the electrodes were stable over the whole water photolysis run under relatively positive potentials. Their outstanding performance was explained by the coupling of two charge transfer mechanisms occurring in core–shell architectures.

ZnFe₂O₄ is an n-type semiconductor spinel oxide with promising applications in various fields, including photocatalysis. This study reports the successful synthesis of a novel ZnFe₂O₄ derivative based on Prussian Blue Analogues (PBAs) through an electrosynthesis method. To enhance photocatalytic performance, the synthesized ZnFe₂O₄ was employed as a cocatalyst in p-n junction materials, specifically CuO/ZnFe₂O₄. Our findings reveal that introducing ZnFe₂O₄ could significantly improve the photocatalytic activity and hydrogen (H₂) production rate of the CuO/ZnFe₂O₄ system compared to bare CuO. This enhancement was sustained over an extended operational period, indicating the material's potential for long-term use in photocatalytic applications. The superior performance of the ZnFe₂O₄ cocatalyst is attributed to its efficient charge separation and improved light absorption properties, which collectively contribute to higher photocatalytic efficiency. This study highlights the potential of PBA-based derivative ZnFe₂O₄ as an effective cocatalyst in developing advanced photocatalytic systems for sustainable hydrogen production.

Copper(I) oxide (Cu₂O)-based photocathodes are promising materials for carbon dioxide (CO₂) reduction under visible light due to copper’s abundance and favorable energy band alignment. However, Cu₂O suffers from photocorrosion and chemical instability. Here, we present a novel approach utilizing a porous titanosilicate material (ETS-10) as a protective layer for Cu₂O, addressing these limitations. The Cu₂O was electrodeposited and coated with a thin ETS-10 layer, which prevents photocorrosion, enhances charge separation and transfer, and facilitates CO₂ capture through its highly porous structure. Comprehensive structural, compositional, and morphological analyses confirmed that ETS-10 effectively stabilized Cu₂O while maintaining its electronic properties (UV–Vis, XPS). The Cu₂O/ETS-10 photocathode exhibited a 25% enhancement in the photocurrent density at 0.0–0.1 V vs. RHE and significantly improved stability compared to bare Cu₂O. The thin ETS-10 layer acted as a passivation layer, improving charge transfer via tunneling mechanisms. This study introduces a multicomponent photocathode system, demonstrating a new application of ETS-10 in photoelectrochemical cells. The results highlight the potential of ETS-10 to enhance the efficiency and stability of photocathodes, offering a pathway for the design of advanced systems for solar-driven CO₂ reduction and artificial photosynthesis.