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Overcoming one of most challenging limitations of bare TiO₂ with large bandgap can be achieved by rational design and fabrication of heterostructures. Multicomponent sulfides with a nature of tunable band structure can be a good alternative to decorating TiO₂, but there remains a major trade-off between the high efficiency and the long-term durability, so the stability issue must be addressed upon the use of sulfides. Here, an effective strategy is demonstrated with Bi-doped AgIn₅S₈ (Bi-AgIn₅S₈) decorated TiO₂ photoanode, where twofold enhancement of the photocurrent is achieved. More importantly, it is the first time to integrate polydopamine passivation layer and AgIn₅S₈ for simultaneously enhancing the solar conversion efficiency and stability. The incident photon-to-current conversion efficiency value is tuned up to 45% (0.4 V vs Ag/AgCl), and the photocurrent density can keep for 90.8% after 5 h. Corresponding hydrogen evolution rate has increased to 8.6 µmol h⁻¹, which is three times higher than that of bare TiO₂.

Integration of polydopamine (PDA)/Bi-AgIn₅S₈/TiO₂ can simultaneously enhance the solar conversion efficiency and stability. The hydrogen evolution rate of optimal sample is enhanced to 8.6 µmol h⁻¹, which is three times higher than that of bare TiO₂.

A 3D hierarchical porous catalyst architecture based on earth abundant metals Ni, Fe, and Co has been fabricated through a facile hydrothermal and electrodeposition method for efficient oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The electrode is comprised of three levels of porous structures including the bottom supermacroporous Ni foam (≈500 μm) substrate, the intermediate layer of vertically aligned macroporous NiCo₂O₄ nanoflakes (≈500 nm), and the topmost NiFe(oxy)hydroxide mesoporous nanosheets (≈5 nm). This hierarchical architecture is binder-free and beneficial for exposing catalytic active sites, enhancing mass transport and accelerating dissipation of gases generated during water electrolysis. Serving as an anode catalyst, the designed hierarchical electrode displays excellent OER catalytic activity with an overpotential of 340 mV to achieve a high current density of 1200 mA cm⁻². Serving as a cathode catalyst, the catalyst exhibits excellent performance toward HER with a moderate overpotential of 105 mV to deliver a current density of 10 mA cm⁻². Serving as both anode and cathode catalysts in a two-electrode water electrolysis system, the designed electrode only requires a potential of 1.67 V to deliver a current density of 10 mA cm⁻² and exhibits excellent durability in prolonged bulk alkaline water electrolysis.

A freestanding, bifunctional NiFe nanosheet/NiCo₂O₄ nanoflake/Ni foam electrode is reported for water splitting. The electrode exhibits extraordinary catalytic activity toward both oxygen evolution and hydrogen evolution reactions in alkaline media, comparable to the state-of-the-art catalysts including noble metal based catalysts. The unique multiple hierarchical porous architecture offers significantly enlarged reactive surface area and abundant synergistic effects for water splitting.