As the demand for renewable energy continues to increase, solar energy has attracted widespread attention as a clean and abundant energy source. Solar photoelectrochemical water splitting is considered a promising technology for efficient, sustainable, and scalable solar hydrogen production. Since Fujishima and Honda first demonstrated photoelectrochemical water splitting with TiO2 photoanode in 1972, this technology has been a hot area of research . However, there are challenges in realizing efficient, stable, and scalable photoelectrochemical water splitting systems. Previous research has shown that meeting these requirements simultaneously is a difficult task because improving performance in one aspect often leads to performance degradation in other aspects.
In order to solve this problem, scientists continue to explore new materials and technologies. In the past few decades, stable oxide semiconductors such as TiO 2 , Fe 2 O 3 , WO 3 and BiVO 4 have been widely used in the preparation of photoanodes, but their charge transport properties and energy gaps are not suitable for implementation Efficient light energy conversion. To overcome this problem, researchers have been exploring new materials, among which organic-inorganic metal halide perovskite (PSK) materials have attracted great attention. These materials have excellent charge transport properties and tunable energy gaps, providing ideal properties for the preparation of efficient photoelectrodes. However, the instability of PSK materials in aqueous electrolytes makes them challenging in photoelectrochemical water splitting. Although there have been some attempts to utilize PSK materials for water splitting, the results of these attempts have been unsatisfactory due to PSK's low activity, instability, and lack of appropriate passivation layers or electrocatalysts.
In view of this, Hankwon Lim, Ji-Wook Jang, Sang Il Seok and Jae Sung Lee of the Ulsan National Institute of Science and Technology in South Korea published an unassisted photoelectrochemical water splitting system based on all-perovskite in Nature Energy for efficient and stable and scalable solar hydrogen production (All-perovskite-based unassisted photoelectrochemical water splitting system for efficient, stable and scalable solar hydrogen production). This study proposes a new all-perovskite (FAPbI 3 ) photon The anode, by encapsulating it on Ni foil and loading NiFeOOH electrocatalyst, achieves efficient, stable and scalable performance. The results also demonstrate an all-perovskite-based unassisted photoelectrochemical water splitting system composed of the photoanode and FAPbI3 solar cells in parallel, achieving satisfactory efficiency. Finally, the photoanode was successfully scaled up from small to large sizes, demonstrating its good performance during the scale-up process. This research result not only provides new materials and methods for realizing efficient, stable and scalable solar hydrogen production systems, but also takes an important step towards promoting photoelectrochemical water splitting technology towards practical applications.
Research content
In the process of solving the problems of high efficiency, stability and scalability of photoelectrochemical water splitting systems, researchers successfully synthesized a new type of all-perovskite ( FAPbI3 ) photoanode for the first time by encapsulating and loading it on Ni foil. The NiFeOOH electrocatalyst achieves effective protection of the FAPbI3 layer and prevents moisture penetration, thus improving the stability of the photoanode. In addition, an all-perovskite-based unassisted photoelectrochemical water splitting system was constructed, and a mini-module was developed by connecting a 2×2 amplified NiFeOOH/Ni/ FAPbI 3 photoanode array (two cells, 7.68 cm^2) in parallel. (2×2 array, 30.8 cm^2) and placed in a solar water splitting panel reactor filled with electrolyte. This innovative design demonstrates significant scientific contributions in achieving efficient solar water splitting (see Figure 1).
Figure 1. NiFeOOH/Ni/FAPbI 3 photoanode and all-perovskite-based unassisted PEC mini-module
In order to characterize the performance of this new photoanode, the researchers utilized a variety of characterization methods (see Figure 2). First, they observed the complete FAPbI3 thin-film photovoltaic device through high-resolution scanning electron microscopy (SEM) , revealing the good interface connections between the functional layers. The structure of the photoanode is optimized and includes appropriate thicknesses of TiO 2 layers (70 nm and 150 nm), FAPbI 3 layers (550 nm), Spiro-OMeTAD layers (150 nm), and Au layers (70 nm). The Tauc plot obtained from the ultraviolet-visible (UV-vis) absorption spectrum reveals the band gap energy of FAPbI 3 , while the photocurrent spectrum (EQE) and photocurrent density-voltage curve (JV curve) demonstrate the superior performance of the photovoltaic cell.
Figure 2. Performance of FAPbI 3 photovoltaic cells with structural and n–i–p structures.
Next, the researchers designed an all-perovskite-based unassisted photoelectrochemical water splitting system connected to an enlarged 2 × 2 array of NiFeOOH/Ni/FAPbI photoanodes . Through the measured current-voltage (JV) curves, they demonstrated the operating points of two devices (small size, 0.25 cm2 ) in a two-electrode setup, revealing the performance of the photoelectrochemical-photovoltaic system under its operating conditions ( See Figure 3).
Figure 3. Device structure and PEC performance of n–i–p structured NiFeOOH/Ni/FAPbI 3 photoanode
Further studies demonstrated the OEC/Ni/FAPbI structure of this novel photoanode , utilizing NiFeOOH, NiOOH and FeOOH as oxygen evolution catalysts. By measuring current-voltage curves, open circuit potential, Nyquist plots, and chemical stability under water oxidation conditions, the researchers compared the effects of different OECs on photoanode performance and stability (see Figure 4).
Figure 4. Charge transport, separation and transfer kinetics of OEC/Ni/FAPbI 3 photoanodes with different OECs (NiFeOOH, NiOOH and FeOOH) and their effects on photoanode activity and stability
Finally, to demonstrate the well-maintained performance of this new photoanode during size enlargement, the researchers designed a 2 × 2 array large-scale photoelectrochemical water splitting system. Using current-voltage curves measured in a two-electrode setup, the researchers elucidated the operating point of the photocell during amplification and demonstrated the stability of the large-sized photoanode. Finally, they demonstrated practical applications of this innovative photovoltaic cell in an experimental setup, including the assembly of single photovoltaic cells, multiple reactors, and large modules (see Figure 5).
Figure 5. Scale-up demonstration of NiFeOOH/Ni/FAPbI 3 photoanode mini-module for unassisted PEC water splitting system
Outlook
This article demonstrates a new, efficient and feasible solar hydrogen production technology, which provides strong support for the future clean energy field. By successfully synthesizing an all-perovskite (FAPbI 3 ) photoanode and applying it in a photoelectrochemical water splitting system, a significant breakthrough has been achieved in improving efficiency, maintaining stability, and achieving scalability. The innovation of this research lies in resolving the contradiction between material stability and efficiency in traditional photoelectrochemical systems. By encapsulating and loading electrocatalysts, the material's instability in aqueous electrolytes was successfully overcome while improving the efficiency of photovoltaic cells.
In addition, this article also maintains stable performance during the size expansion process of the all-perovskite photoelectrochemical system, providing feasibility for practical applications.
Original details:
Hansora, D., Yoo, J.W., Mehrotra, R. et al. All-perovskite-based unassisted photoelectrochemical water splitting system for efficient, stable and scalable solar hydrogen production. Nat Energy (2024).
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