cm6b01522_si_001.pdf (2.78 MB)
Iron-Doped Nickel Phosphate as Synergistic Electrocatalyst for Water Oxidation
journal contribution
posted on 2016-07-31, 00:00 authored by Yibing Li, Chuan ZhaoElectrochemical
water splitting into hydrogen and oxygen has been
regarded as one of the most promising approaches to produce clean
hydrogen fuel using electricity generated from renewable energy sources
such as solar energy, wind power, or hydropower etc. Recent findings
have demonstrated significant potential of nonprecious, nickel-based
electrocatalysts as efficient oxygen evolution reaction (OER) to replace
traditional ruthenium (Ru) and iridium (Ir)-based precious metal catalysts.
Here, for the first time, we report a novel three-dimensional iron-doped
nickel phosphate catalyst by stepwise autologous hydrothermal growth
of nickel phosphate (Ni:Pi) spontaneously from nickel foam (NF) followed
by electrodeposition of iron hydroxide (denoted as Ni:Pi-Fe/NF). Our
findings reveal that the incorporated iron could play strong synergistic
effects on the OER activities of nickel phosphate in alkaline solution,
delivering a current density of 10 mA cm–2 at an
extremely small overpotential (η) of 220 mV and extraordinary
high current density of 500 mA cm–2 at η =
290 mV in 1 M KOH, which is among the best Ni-based OER electrocatalysts
to date. Furthermore, in a concentrated alkaline electrolyte (5 M
KOH), the Ni:Pi-Fe/NF electrode can reach a high current density of
1 600 mA cm–2 at an overpotential merely
of 332 mV and shows excellent electrocatalytic stability in prolonged
bulk water electrolysis, meaning it could highly meet the requirement
of the industry alkaline electrolysis system. Mechanism investigations
employing X-ray photoelectron spectroscopy (XPS), electrochemical
polarization, contact angle measurement, and Raman spectra suggest
strong interactions between Ni:Pi and Fe, with nickel oxyhydroxide
(NiOOH) being the primary catalytic active site and nickel phosphate
facilitating water adsorption. The iron doping changes the local Ni–O
environments which synergistically enhance the Ni:Pi-Fe/NF catalytic
activity toward OER.