Ultraviolet assisted defects engineering of metal organic frameworks towards high performance oxygen evolution reaction

Hydrogen production from water splitting has gained tremendous interest as an alternative to fossil fuels, while the sluggish nature of the four-electron process during oxygen evolution reaction (OER) has impeded its practical applications. Here, we report the ultraviolet (UV) assisted OER enhancement of NiFe Prussian blue analogues (PBAs) by the creation and stabilization of new active sites. UV treatment induces the cleavage of certain M-C/M-N (M: Ni or Fe) bonds and the removal of CN groups, thereby increasing the number of active sites. Additionally, due to the breaking of M-C/M-N bonds, OH⁻ functional groups readily bonded to Fe sites, transforming them into active sites that require only three-electrons for the OER process. The optimally treated sample exhibited superior OER performance, with an overpotential of 279 mV, a Tafel slope of 52.0 mV dec⁻¹, a mass activity of 733.33 A g⁻¹ and a turnover frequency of 2.48 s⁻¹ compared to pristine PBA which showed values of 409 mV, 134.6 mV dec⁻¹, 28.83 A g⁻¹_, and 0.10 s⁻¹, respectively. Density functional theory (DFT) calculations further confirm lower reaction energy barrier for OER after UV irradiation. Moreover, UV treatment could serve as a universal strategy to enhance the OER performance of other types of metal organic frameworks-based catalysts.