Defect-Passivated Perovskite Photoanode coupled with Iodide Oxidation Reaction enabling Efficient Stable Unbiased Hydrogen Production

Defect-passivated perovskite photoanode coupled with iodide oxidation reaction enabling efficient stable unbiased hydrogen production<br/><br/>Juwon Yun, Young Sun Park, Hyungsoo Lee, Wooyong Jeong, Chang-Seop Jeong, Chan Uk Lee, Jeongyoub Lee, Subin Moon, Soobin Lee, Sumin Kim, Junhwan Kim, and Jooho Moon*<br/><br/><i>¹Department of Materials Science and Engineering, Yonsei University</i><br/><i>50 Yonsei-ro Seodaemun-gu, Seoul 120-749, Korea</i><br/>*E-mail address : [email protected]<br/><br/>The unassisted photoelectrochemical (PEC) hydrogen production is one of the promising candidates to replace the carbon-based energy sources. However, the previously reported photoanodes have suffered from low efficiency resulting from poor light absorption and limited charge separation capability. Lead halide perovskite has emerged as a promising breakthrough to overcome the limitations of conventional photoanode materials (such as BiVO₄, Fe₂O₃, Ta₃N₅, Sb₂S₃, and WO₃) owing to its tunable bandgaps, excellent hole mobility, and long hole-diffusion length. These superior properties enable perovskite-based photoanode to achieve remarkable high-performance parameters including a photovoltage of ~ 1.1 V and a photocurrent density of around 23 mA cm^-2. However, there are still challenges in achieving competitive hydrogen production, particularly in terms of onset potential and long-term stability. The poor onset potential can be attributed to the high thermodynamic potential (1.23 V with respect to reversible hydrogen electrode (V_RHE)) required for the oxygen evolution reaction (OER) and the sluggish kinetics of OER involving a four-electron transfer process. Moreover, the charge accumulation due to interfacial defects and slow charge transfer reaction result in efficiency loss and photoelectrode degradation.<br/>Herein, we report a straightforward strategy to improve the onset potential and durability of perovskite photoanode. This approach involves simple defect passivation method by decorating 4-methoxyphenethylamine on electron transport layer (ETL)_,effectively suppressing efficiency loss and charge accumulation at ETL/perovskite interface. Furthermore, we replace the OER with the iodide oxidation reaction (IOR) by employing an active IOR catalyst (Co_0.2Ni₃S₂) to enhance the kinetics of charge transfer reaction. The combined effects of interface engineering and the IOR catalyst are manifested by the enhanced PEC performance and stability. The perovskite photoanode reveals a -0.2 V_RHE onset potential and improved fill factor along with a high durability for 200 h. We additionally demonstrate unbiased hydrogen production consisting of single perovskite photoanode and Pt catalyst achieving the operation current of 12 mA cm^-2 and stable operation for 24 h.