Electronic Feature Modification of Ni and Co Free Metal-Organic Framework Nanoparticles by Vanadium Introduction for Water Oxidation

Abstract

Electrocatalytic water splitting has emerged as an innovative technique for producing green hydrogen fuel. In this regard, a series of electrocatalysts based on Ni and Co have been investigated for improved oxygen evolution activity. However, the reliance on Ni and Co constraints the development of cost-effective electrocatalysts and presents challenges for advancing innovation in this field. In this work, we developed Ni- and Co-free VFe-MOF nanoparticles exhibiting remarkable electrocatalytic performance for electrocatalytic water oxidation. Spectroscopic analysis revealed that the V-introduction induced easier access to high valent Fe3+ due to its electronic withdrawing nature altering the electronic features of the Fe-MOF. Easier access of Fe3+ led to the accessible O-O bond formation, boosting the catalytic reactivity. Consequently, VFe-MOF nanoparticles achieved superior oxygen evolution reaction (OER) activity, surpassing the performance of CoFe- and NiFe-MOF counterparts. It demonstrated a notably low overpotential of 220 mV at a current density of 10 mA cm-2, outperforming Fe-MOF, CoFe-MOF, and NiFe-MOF. The incorporation of high-valent vanadium significantly enhanced the electronic properties of the Fe-MOF, accelerating OER kinetics and increasing the number of reactive sites and surface area, which collectively boosted catalytic performance. Additionally, the VFe-MOF achieved a high faradaic efficiency (FE) of 97.6% for OER, reflecting its intrinsic catalytic efficacy. Postcatalytic analysis indicated that VFe-MOF undergoes electrochemical reconstruction into an active Fe(O)OH phase, which serves as the true active species for OER. © 2024 American Chemical Society.