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Energy harvesting from solar and water has created ripples in materials energy research for the last several decades, complemented by the rise of Hydrogen as a clean fuel. Among these, water electrolysis leading to generation of oxygen and hydrogen, has been one of the most promising routes towards sustainable alternative energy generation and storage, with applications ranging from metal-air batteries, fuel cells, to solar-to-fuel energy conversion systems. In fact, solar water splitting is one of the most promising method to produce Hydrogen without depleting fossil-fuel based natural resources. However, the efficiency and practical feasibility of water electrolysis is limited by the anodic oxygen evolution reaction (OER), which is a kinetically sluggish, electron-intensive uphill reaction. A slow OER process also slows the other half- cell reaction, i.e. the hydrogen evolution reaction (HER) at the cathode. Hence, designing efficient catalysts for OER process from earth-abundant resources has been one of the primary concerns for advancing solar water splitting. In the Nath group we have focused on transition metal chalcogenides as efficient OER electrocatalysts. We have proposed the idea that these chalcogenides, specifically, selenides and tellurides will show much better OER catalytic activity due to increasing covalency around the catalytically active transition metal site, compared to the oxides caused by decreasing electronegativity of the anion, which in turn leads to variation of chem. potential around the transition metal center, [e.g. lowering the Ni 2+ --> Ni 3+ oxidn. potential in Ni-based catalysts where Ni 3+ is the actually catalytically active species]. Based on such hypothesis, we have synthesized a plethora of transition metal selenides including those based on Ni, Ni-Fe, Co, and Ni-Co, which show high catalytic efficiency characterized by low onset potential and overpotential at 10 mA/cm 2 [Ni 3 Se 2 - 200 - 290 mV; Co 7 Se 8 - 260 mV; FeNi 2 Se 4 -NrGO - 170 mV (NrGO - N-doped reduced graphene oxide); NiFe 2 Se 4 - 210 mV; CoNi 2 Se 4 - 190 mV; Ni 3 Te 2 - 180 mV].
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Water Splitting Electrocatalysis within Layered Inorganic Nanomaterials
The conversion of solar energy into chemical fuel is one of the “Holy Grails” of 21st century chemistry. Solar energy can be used to split water into oxygen and protons, which are then used to make hydrogen fuel. Nature is able to catalyze both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) required for the conversion of solar energy into chemical fuel through the employment of enzymes that are composed of inexpensive transition metals Instead of using expensive catalysts such as platinum, cheaper alternatives (such as cobalt, iron, or nickel) would provide the opportunity to make solar energy competitive with fossil fuels. However, obtaining efficient catalysts based on earth abundant materials is still a daunting task. Progress in finding an ideal catalyst for the OER has been challenging as it appears that the overpotential for these catalysts have plateaued. Recent theory has shown that nanoscopic confinement of catalysts into 3D frameworks increases stability and efficiency of catalysts for OER. We are studying the use of the layered inorganic nanomaterial zirconium phosphate (ZrP) for water splitting. In this chapter we review the advancements made with ZrP as a support for transition metals for the OER. Our studies have found that ZrP is a suitable support for transition metals as it provides an accessible surface where the OER can occur. Further findings have also show that exfoliation of ZrP increases the availability of sites where active species can be adsorbed and performance is improved with this strategy.
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- Award ID(s):
- 1827622
- PAR ID:
- 10608681
- Publisher / Repository:
- IntechOpen
- Date Published:
- ISBN:
- 978-1-78985-557-9
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Book Chapter:
- https://doi.org/10.5772/intechopen.88116
