Hydrazine-Assisted Acidic Water Splitting Driven by Iridium Single Atoms

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• Water splitting for hydrogen production typically requires high voltages (>1.5 V), limiting single-atom catalyst stability, especially in acidic media.
• Oxygen evolution reaction (OER) is a bottleneck in water splitting due to high overpotential and stability issues.
• Replacing OER with hydrazine oxidation reaction (HzOR) can reduce overall voltage requirements.

Purpose of the Study:

• To investigate the efficacy of iridium single-atom catalysts supported on nitrogen-doped carbon (Ir-SA/NC) for hydrogen evolution reaction (HER) and HzOR.
• To evaluate the stability and activity of Ir-SA/NC in acidic electrolytes (0.5 M H2SO4).
• To elucidate the reaction pathway of HzOR on Ir-SA/NC.

Main Methods:

• Synthesis and characterization of Ir-SA/NC electrocatalyst.
• Electrochemical measurements for HER and HzOR in 0.5 M H2SO4.
• In situ Raman spectroscopy to study the HzOR mechanism.

Main Results:

• Ir-SA/NC exhibited a high mass activity of 37.02 A mgIr−1 for HER at 50 mV overpotential, 127 times higher than Pt/C.
• For HzOR, Ir-SA/NC achieved 10 mA cm−2 at a low potential of 0.39 V vs RHE, significantly lower than OER (1.5 V vs RHE).
• Ir-SA/NC demonstrated superior stability in HzOR catalysis and an 83-fold enhanced mass activity compared to Pt/C at 0.5 V vs RHE.

Conclusions:

• Ir-SA/NC is a robust electrocatalyst for both HER and HzOR in acidic media.
• Hydrazine-assisted water splitting using Ir-SA/NC operates at a substantially reduced voltage (0.39 V), offering a 1.25 V saving compared to acidic water splitting.
• The proposed HzOR pathway on Ir-SA/NC involves N2H4 →*2NH2 →*2NH→2N→*N2 →N2.