Surface-Passivated Vertically Oriented Sb₂S₃ Nanorods Photoanode Enabling Efficient Unbiased Solar Fuel Production

The lack of highly efficient photoanodes presents a significant challenge to implementing the promising strategy of unbiased solar-to-fuel conversion. To achieve high-performance photoanodes, improving their light harvesting and charge separation/injection capabilities is indispensable. Herein, solution-processed vertically oriented Sb₂S₃ nanorod arrays on substrate are obtained via a Au seed layer, resulting in improved optoelectronic properties (due to the light scattering effect) and favorable crystallographic orientation of the 1D nanostructure. Moreover, the (NH₄)₂WS₄ treatment caps the surface of the nanorods with an amorphous WS_x layer and passivates the sulfur vacancy of Sb₂S₃, resulting in boosted charge extraction to the reactants. The resulting photoanode is employed to drive an iodide oxidation reaction (IOR), which is a prominent alternative to sluggish water oxidation reactions, exhibiting a high photocurrent density of 13 mA cm⁻² at 0.6 V versus the reversible hydrogen electrode. Subsequently, an unassisted hydrogen generation device is demonstrated by combining an Sb₂S₃ nanorod array-based photoanode for IOR and a perovskite-based photocathode for the hydrogen evolution reaction, achieving an efficient hydrogen production current density of 5.7 mA cm⁻² without any external bias.