Defect-Rich UiO-66-NH2/LDHs for Photocatalytic Hydrogen Generation from Seawater

Abstract

In this work, defect-rich UiO-66-NH2 metal–organic framework (MOF) anchoring on flower-like NiCo layered double hydroxides (LDH), was developed for enhanced photocatalytic performance. Various analytical methods including positron annihilation lifetime spectroscopy (PALS) revealed that deuteration reduced defect-related free volume and modified positron trapping, indicating structural densification and improved charge carrier separation. Thermogravimetric analysis (TGA) confirmed the presence of structural defects, affecting thermal stability and facilitating enhanced catalytic activity. This was further supported by the X-ray photoelectron spectroscopy (XPS) which identified dominated Zr3+ states in Defect UiO-66-NH2 (UiO-66-NH2-D), signifying electronic alterations that contribute to improved photocatalytic performance. Spectroscopic & electrochemical analysis demonstrated an extended charge carrier lifetime, and minimum charge transfer resistance indicating suppressed recombination rates in the defect-engineered system compared to defect-free MOF. Benefiting by the synergistic interactions between UiO-66-NH2-D and NiCo-LDH, the UiO-66-NH2-D/NiCo-LDH heterostructure composite achieves H₂ production rate of 7.6 mmol g−1 h−1 which is 2.18 and 3.5 times higher than UiO-66-NH2-D and pristine UiO-66-NH2, respectively, via seawater splitting. This study paves the way for developing defect-engineered MOF-based composites for renewable energy applications, particularly in utilizing seawater directly for hydrogen production.