Abstract
Zirconium phosphate (ZrP), an inorganic layered nanomaterial, is currently being investigated as a catalyst support for transition metal-based electrocatalysts for the oxygen evolution reaction (OER). Two metal-modified ZrP catalyst systems were synthesized: metal-intercalated ZrP and metal-adsorbed ZrP, each involving Fe(II), Fe(III), Co(II), and Ni(II) cations. Fourier transform infrared spectroscopy, X-ray powder diffraction, thermogravimetric analysis, and X-ray photoelectron spectroscopy were used to characterize the composite materials and confirm the incorporation of the metal cations either between the layers or on the surface of ZrP. Both types of metal-modified systems were examined for their catalytic activity for the OER in 0.1 M KOH solution. All metal-modified ZrP systems were active for the OER. Trends in activity are discussed as a function of the molar ratio in relation to the two types of catalyst systems, resulting in overpotentials for metal-adsorbed ZrP catalysts that were less than, or equal to, their metal-intercalated counterparts.
Highlights
The renewable, sustainable production of hydrogen could have many benefits, displacing the conventional fossil-based processes for its production and use in the fuels and chemical industry, and potentially serving as an alternative energy vector given its high gravimetric energy density and modularity of use [1]
For the catalyst systems studied here in alkaline electrolyte, we generally find that the metal-adsorbed zirconium phosphate (ZrP) catalysts are more active than their intercalated counterparts, e.g., a metal-adsorbed Fe(II)-ZrP at a 10:1 Fe(II):ZrP molar ratio that requires an overpotential of 490 mV at 10 mA/cm2, while its metal-intercalated counterpart at the same molar ratio requires an overpotential of 520 mV at 10 mA/cm2
The intercalant species will displace interlayer water molecules. Bands associated with these water vibrational modes will show reduced relative intensity in the intercalated materials; the IR data shown in Figure 2A is consistent with intercalation of the metal species into
Summary
The renewable, sustainable production of hydrogen could have many benefits, displacing the conventional fossil-based processes for its production and use in the fuels and chemical industry, and potentially serving as an alternative energy vector given its high gravimetric energy density and modularity of use [1]. OER catalysts suffer from considerable overpotential losses, limiting the efficiency of hydrogen generation by water electrolysis processes [11]. To overcome these challenges and to facilitate the economic viability of electrolysis, the efficiencies of electrolyzer systems must be improved by addressing the kinetic overpotential. The use of the zirconium phosphate (ZrP) type of layered inorganic compounds, a support for water oxidation catalysts, is examined. The most extensively studied phase of ZrP is as a support for water oxidation catalysts, is examined. The layered structure of ZrP is leveraged to support active catalysts for the OER through the ion exchange of transition metal cations. For the catalyst systems studied here in alkaline electrolyte, we generally find that the metal-adsorbed ZrP catalysts are more active than their intercalated counterparts, e.g., a metal-adsorbed Fe(II)-ZrP at a 10:1 Fe(II):ZrP molar ratio that requires an overpotential of 490 mV at 10 mA/cm , while its metal-intercalated counterpart at the same molar ratio requires an overpotential of 520 mV at 10 mA/cm
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