A ligand-specific bimetallic electrocatalyst for efficient oxygen evolution reaction at higher current density

Abstract

The oxygen evolution reaction (OER) is a critical and bottleneck process in electrochemical energy applications. This study presents a straightforward hydrothermal method for preparing a NiCo bimetallic organic framework (NiCo-MOF) with three unique ligands. The NiCo-trimesic acid-based MOF on carbon cloth (NiCo-t-MOF/CC) can sustain the industrially relevant current density of 100 mA cm⁻² for over 62 hours despite the observed gradual increase in potential in 1 M KOH without replacing the electrolyte. The NiCo-t-MOF/CC electrocatalyst achieved a significantly lower overpotential of 440 mV to reach a current density of 100 mA cm⁻², outperforming the benchmark RuO₂ catalyst, which required 581 mV. A Tafel slope of 83 mV dec⁻¹ at NiCo-t-MOF/CC indicates faster oxygen evolution kinetics than at RuO₂/CC (97 mV dec⁻¹). Interestingly, NiCo-t-MOF/CC||Pt–C/CC exhibited a relatively diminished cell voltage of 1.54 V to deliver a current density of 10 mA cm⁻², which is close to the thermodynamic water splitting energy of 1.23 V. The performance of NiCo-t-MOF/CC is promising at higher current densities for industrial applications.