by Researchers at Ulsan National Institute of Science and Technology (UNIST) have developed a scalable and efficient photoelectrochemical (PEC) system for green hydrogen production. Their innovative system, outlined in a paper published in Nature Energy, is based on a formamidinium lead triiodide (FAPbI3) perovskite-based photoanode encapsulated by an Ni foil/NiFeOOH electrocatalyst.
Water splitting, through the use of solar energy or other renewables, holds great promise for sustainable hydrogen production on a large scale. However, most photoelectrochemical water splitting systems proposed so far have proven to be inefficient, unstable, or difficult to implement on a large scale.
Jae Sung Lee, Professor of Energy & Chemical Engineering at UNIST and co-author of the paper, explains, “Our group has thoroughly studied the challenges associated with practical solar hydrogen production. As summarized in our most recent review paper, a minimum efficiency of 10% solar-to-hydrogen (STH) is required to develop a viable practical PEC system, for which selecting an efficient material is the first criterion.”
Previous attempts at photoelectrochemical hydrogen production have generally used metal oxides as the photoelectrode materials of PEC cells. Unfortunately, these systems have yielded efficiencies that are far below what is necessary for practical application.
To address this issue, some researchers have been investigating the potential of using photovoltaic (PV) grade materials, such as silicon, perovskites, chalcogenides, and III-V material classes, as photoelectrodes. While these materials are known for their remarkable efficiencies, they can be expensive and unstable when placed in water, which is essential for PEC water splitting cells.
Lee points out that unlike other PV grade materials, metal-halide perovskites (MHP) have unique characteristics of high efficiency and low cost, making them a potential alternative. However, their stability in humid conditions and under UV light poses a critical challenge.
To overcome this challenge, the researchers stabilized the MHPs using metal-encapsulation or metal-protection techniques, along with the use of UV-stable FAPbI3 perovskite. This allowed them to devise effective photoelectrodes based on MHPs with the necessary stability for hydrogen production.
Another challenge in practical applications is scalability. The high efficiency achieved in laboratory cells, which are typically less than 1 cm2 in size, needs to be maintained in large-scale implementations. For their study, the researchers selected the most advanced MHP material in terms of efficiency and stability (FAPbI3) and encapsulated it with a thick nickel foil (30 mm) deposited with an NiFeOOH catalyst to protect the MHP in water and promote the oxygen evolution reaction for water splitting.
In initial tests, the researchers demonstrated the efficiency and stability of their system in a small-scale version, with a photoelectrode below 1 cm2 in size. The laboratory-scale system achieved a 9.89% STH efficiency and exhibited long-term stability.
This breakthrough in scalable and efficient photo electrochemical systems brings us closer to realizing the sustainable production of green hydrogen. With further development and optimization, this technology could play a significant role in the transition to a greener and more sustainable future.
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1. Source: Coherent Market Insights, Public sources, Desk research
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