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Hydrogen production techniques based on solar-water splitting have emerged as carbon-free energy systems. Many researchers have developed highly efficient thin-film photoelectrochemical (PEC) devices made of low-cost and earth-abundant materials. However, solar water splitting systems suffer from short lifetimes due to catalyst instability that is attributed to both chemical dissolution and mechanical stress produced by hydrogen bubbles. A recent study found that the nanoporous hydrogel could prevent the structural degradation of the PEC devices. In this study, we investigate the protection mechanism of the hydrogel-based overlayer by engineering its porous structure using the cryogelation technique. Tests for cryogel overlayers with varied pore structures, such as disconnected micropores, interconnected micropores, and surface macropores, reveal that the hydrogen gas trapped in the cryogel protector reduce shear stress at the catalyst surface by providing bubble nucleation sites. The cryogelated overlayer effectively preserves the uniformly distributed platinum catalyst particles on the device surface for over 200 h. Our finding can help establish semi-permanent photoelectrochemical devices to realize a carbon-free society. Photoelectrodes made of earth-abundant materials can contribute to low-cost and carbon-free hydrogen production, but suffer from a short lifetime. Here the authors report cryogel overlayer to increase the operation time of the device by regulating evolving hydrogen bubble dynamics. [ABSTRACT FROM AUTHOR]

To achieve a high solar‐to‐hydrogen (STH) conversion efficiency, delicate strategies toward high photocurrent together with sufficient onset potential should be developed. Herein, an SnS semiconductor is reported as a high‐performance photocathode. Use of proper sulfur precursor having weak dipole moment allows to obtain high‐quality dense SnS nanoplates with enlarged favorable crystallographic facet, while suppressing inevitable anisotropic growth. Furthermore, the introducing Ga2O3 layer between SnS and TiO2 in SnS photocathodes efficiently improves the charge transport kinetics without charge trapping. The SnS photocathode reveals the highest photocurrent density of 28 mA cm−2 at 0 V versus the reversible hydrogen electrode. Overall solar water splitting is demonstrated for the first time by combining the optimized SnS photocathode with a Mo:BiVO4 photoanode, achieving a STH efficiency of 1.7% and long‐term stability of 24 h. High performance and low‐cost SnS photocathode represent a promising new material in the field of photoelectrochemical solar water splitting. [ABSTRACT FROM AUTHOR]

Interface modification with para -aminobenzoic acid passivated the interface states, causing rapid photoelectron transport through the Sb 2 Se 3 /TiO 2 interface and resulting in high onset potential and photocurrent density in the photocathode for photoelectrochemical water splitting. • Surface defects in Sb 2 Se 3 photocathode limit the photovoltage development. • Interface modification not only passivates the interface states, but also allows rapid photoelectron transport. • Record-high onset potential, photocurrent density, and half-cell solar-to-hydrogen efficiency are achieved. Achieving both high onset potential and photocurrent in photoelectrodes is a key challenge while performing unassisted overall water splitting using tandem devices. We propose a simple interface modification strategy to maximize the performance of polycrystalline Sb 2 Se 3 photocathodes for photoelectrochemical (PEC) water splitting. The para -aminobenzoic acid (PABA) modification at Sb 2 Se 3 /TiO 2 interface enhanced both the onset potential and photocurrent of the Sb 2 Se 3 photocathodes. The surface defects in the polycrystalline Sb 2 Se 3 limited the photovoltage production, lowering the onset potential of the photocathode. Surface restoration using the conjugated PABA molecules efficiently passivated the surface defects on the Sb 2 Se 3 and enabled the rapid photoelectron transport from the Sb 2 Se 3 to the TiO 2 layer. The PABA treated Sb 2 Se 3 photocathode exhibited substantially improved PEC performance; the onset potential increased from 0.35 to 0.50 V compared to the reversible hydrogen electrode (V RHE), and the photocurrent density increased from 24 to 35 mA cm−2 at 0 V RHE. [ABSTRACT FROM AUTHOR]