Tuning the band (p and d) center and enhancing the active sites by nitrogen(N) doping on iridium diphosphide (IrP₂) for accelerating pH-universal water electrolysis

Efficient water electrolysis requires highly active electrocatalysts with Pt/RuO₂-like performance, which remain challenging to synthesize. To develop an ideal universal-pH catalyst, we fabricated N-doped noble metal iridium diphosphide (N-IrP₂ @CC) catalyst via three-step synthesis on a carbon cloth substrate. The catalyst showed considerably higher catalytic activity compared with existing transition metal phosphide catalysts due to the P-rich condition and N dopants, achieving an overall water-splitting current density of 100 mA cm⁻² at low operation voltages of 1.56 V and 1.64 V in 0.5 M H₂SO₄ and 1 M KOH, respectively. Density functional theory calculations showed that the N dopant can alter not only the band (d and p) center of Ir and P, but also the charge distribution of the IrP₂ surface. Thus, a highly efficient and robust catalyst was developed for commercial water electrolysis.