Fluoride capping prevents the oxidation product from inhibiting the CeO₂ nanozyme, and increases the oxygen vacancy concentration for more efficient catalysis.

Graphene sheets (chemically reduced), a high modulus and high thermal and electrically conductive material are coupled with yeast cells to form an encapsulating inorganic functional layer. The coupling of the high modulus sheets with the cells increases their stability to osmotic stresses. The sheets also allow the direct visualization of the cells in an electron microscope.

Photoelectrochemical cells (PEC) use solar energy to generate green hydrogen by water splitting and have an integrated device structure. Achieving high solar‐to‐hydrogen conversion (STH) efficiency along with a long operational lifetime in these cells is crucial for the production of low‐cost green hydrogen as a viable energy source. Several functional components, such as photo absorber, charge transport, and catalyst layers are interfaced in these cells to form a compact monolithic device. In this review, therefore, the engineering and design of the individual components of these cells, the interplay between them, and their interfaces are discussed in detail, as these factors determine the overall performance of the cells. The main emphasis is on halide perovskite (HP) photo absorbers, which have emerged as promising materials for use in these cells due to their superior optoelectronic properties. Recent advances in the development of efficient and stable perovskite‐based cells are highlighted and reviewed. The design of catalysts for water splitting and the effect of factors such as pH and supporting cations are also examined. Finally, the scientific challenges and future directions for designing perovskite‐based photoelectrochemical cells are discussed. This review can help researchers further advance this technology toward commercial production of green hydrogen.

Pt, an ideal HER catalyst, is costly, hindering its use in wide-scale applications. Here, we discuss how advances to Pt alloys, heterostructures, and SACs improve Pt atomic utilization for HER, and how spectator ions and pH affect performance.