A rationally thin composite membrane with differentiated pore structure for industrial-scale alkaline water electrolysis

Introduction

Hydrogen energy, an efficient and clean secondary energy source, has garnered significant interest from various countries^{1, 2–3}. In contrast to conventional hydrogen production methods, green hydrogen technology offers a continuous and eco-friendly energy supply, thereby contributing to the advancement of sustainable energy systems^4,5. The water electrolysis hydrogen production technology with scale-up is the key to getting efficient utilization of green hydrogen^6,7. Water electrolysis technologies mainly include alkaline water electrolysis (AWE), proton exchange membrane water electrolysis (PEM), and water electrolysis based on solid oxide electrolysis (SOE) cells. Of these, AWE is the most cost-effective technology for industrial production of green hydrogen^8,9. However, the current AWE technology still suffers from low efficiency and high cost compared to traditional fossil fuel hydrogen production technologies^10,11. Therefore, researchers have developed many methods to improve the efficiency of AWE hydrogen production. For example, exploring efficient and low-cost catalysts^{12, 13, 14–15}, developing high-performance membranes^{16, 17, 18, 19, 20, 21–22}, or reducing material cost and increasing operating pressure and temperature^{23, 24, 25, 26–27}. Among these strategies, developing high-performance membranes is considered one of the most effective and easiest approaches to commercialize^17,28,29.

The membrane plays an essential role in AWE, as it is placed between the cathode and anode, preventing the mixing of hydrogen and oxygen³⁰. Meanwhile, it allows the hydroxide ions in the solution to travel freely between the cathode and the anode. Therefore, the membrane must provide an effective gas barrier for system safety while ensuring good electrolyte penetration and minimal area resistance. Earlier, asbestos was used as a membrane material for AWE³¹, but it has been banned due to its poor conductivity and potential health risks. Recently, the polyphenylene sulfide (PPS) fabric membranes have been used in AWE on a large scale³². However, it still faces changes, including high electrolysis energy consumption during electrolysis and low gas barrier due to its hydrophobic properties and large pore size^33,34. Thus, an increasing number of researchers have sought to improve the hydrophilicity and gas barrier of PPS mesh by applying functional coatings to its surface. For example, Lee et al. reported the synthesis of a Zirfon-type composite...