Ir–O–V Catalytic Group in Ir-Doped NiV(OH)₂ for Overall Water Splitting

Bifunctional electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are very crucial for converting water into clean fuel through overall water splitting. Here, we report on a bifunctional catalyst based on Ir-doped NiV layered double hydroxide with Ir–O–V catalytic groups on which water dissociation, HER, and OER occur on Ir, bridge O, and V atoms, respectively. Interestingly, the dopant Ir ions were found to play a triple role: (i) serve as catalytic sites for water dissociation, (ii) reduce charge density on adjacent bridge oxygen, thus facilitating HER there, and (iii) increase charge density on V ions, which in turn boosts OER. As a result, the catalyst achieves an ultralow applied voltage for overall water splitting (1.49 V @ 10 mA cm–2) and beats the noble metallic couple Pt/C and Ir/C with its value of 1.60 V @ 10 mA cm–2.