posted on 2024-02-21, 13:38authored byYumeng Guo, Xiang Sun, Shaosong Ding, Jun Lu, Huanting Wang, Ying Zhu, Lei Jiang
Engineered
asymmetric heterogeneous ion-selective membranes have
become a focal point for their improved efficiency in harnessing osmotic
energy from ionic solutions with varying salinity. However, achieving
both energy conversion efficiency and excellent chemical stability
necessitates effectively mitigating the formation of detrimental interface
cracks between two different layers. We develop a charge-gradient
sulfonated poly(ether ether ketone) (SPEEK) membrane (CG-SPEEK) on
a large-scale using a straightforward coating method. As an osmotic
energy generator, CG-SPEEK membrane achieves an impressive output
power density of 9.2 W m–2 and exhibits ultrahigh
cation selectivity (0.99), with an energy conversion efficiency of
48% at a 50-fold NaCl concentration gradient. The results highlight
the ion diode effects of CG-SPEEK, driven by a charge density gradient
that accelerates cation transport while suppressing ion concentration
polarization. Density functional theory simulations provide further
insights, revealing that the energy barrier for Na+ ion
transport through CG-SPEEK membrane is lower than that through a homogeneous
SPEEK membrane. This work not only enhances our understanding of ion
transport dynamics but also establishes the CG-SPEEK membrane as a
promising candidate for efficient osmotic energy conversion applications.