Electronic State Modulation of Rhodium Nanoparticles by Coupling with g-C ₃ N ₄ Support for Efficient Overall Water Splitting in Alkaline Medium

The design and synthesis of an efficient, durable, and bifunctional electrocatalyst are essential for effective H 2 production through water splitting. Noble-metal-based nanomaterials have drawn much attention for their high efficiency in electrocatalytic water splitting. However, their effective utilization and durability for long-term operations remain significant challenges. In this context, noble-metal Rh nanoparticles are anchored on the g-C 3 N 4 surface (Rh/g-C 3 N 4 ) as efficient electrocatalysts for water splitting. The high surface area of g-C 3 N 4 provides effective dispersion of Rh nanoparticles for the optimum utilization of metal nanoparticles. Moreover, the significant orbital overlapping between the Rh 4d and C/N 2p orbitals provides strong electronic coupling at the Rh/g-C 3 N 4 interface, which not only facilitates the robust anchoring of Rh nanoparticles but also enhances the electrocatalytic activity. The as-synthesized Rh/g-C 3 N 4 shows improved activity for HER, requiring an overpotential of 38 mV to generate a current density of 10 mA cm –2 . The cell designed by using Rh/g-C 3 N 4 exhibits high activity for overall water splitting in 1 M KOH and requires a cell potential of 1.64 V, with a durability of 108 h. The Bader charge analysis shows significant charge accumulation on the Rh nanoparticles through interfacial charge transfer from the g-C 3 N 4 support. The electron transfer modifies the electronic state of Rh and optimizes the binding energy of hydrogen for improved electrocatalytic performance.