Earth-Abundant Electrocatalysts for the Oxygen Evolution Reaction of Water Splitting Using Nanostructured Layered Inorganic Materials

Abstract

Nature uses solar energy and earth-abundant materials for splitting water into oxygen, in the oxygen evolution reaction (OER), and protons, which are then reduced into hydrogen in the hydrogen evolution reaction (HER). Hydrogen solar fuel produced in artificial photosynthesis schemes for water splitting could be used in fuel cells. Learning from nature, instead of using expensive catalysts such as platinum, cheaper alternatives (such as cobalt, iron, or nickel) would provide the opportunity to make solar energy even more competitive with fossil fuels. However, obtaining efficient catalysts based on earth-abundant materials is still a daunting task, particularly for the OER. Recent theory has shown that nanoscopic confinement of catalysts increases the stability and efficiency of catalysts for OER. We have designed and develop earth-abundant electrocatalysts for oxygen reduction and water splitting using nanostructured layered inorganic materials of zirconium phosphate (ZrP). We have demonstrated improved electrocatalytic activity of ZrP nanomaterials loaded with metal ions suitable for the OER of water splitting. Adsorbing Co or Ni catalysts on the ZrP nanoparticles surface proved to improved OER activity compared to intercalated catalysts. A comparison between adsorbed Co or Ni catalysts and those catalysts on exfoliated ZrP hexagonal nanoplatelets proved that those on exfoliated nanoplatelets were more active, with diminished overpotentials and reduced Tafel plot slopes as well as higher mass activities. More recently, comparison between Co and Ni catalyst on ZrP particles with different morphologies (hexagonal platelets, rods, cubes, and spheres) revealed that the more active Co catalysts are those on hexagonal ZrP platelets, whereas the best Ni catalysts are those on ZrP spheres. Finally, encouraging recent results with a cobalt porphyrin catalyst will be presented, as well as recent XAS operando results. These results demonstrate that ZrP nanoparticles are suitable supports for electrocatalysis of the OER and water splitting.Sponsored by NSF Center for Chemical Innovation in Solar Fuels CHE-1305124 and NSF-PREM Center for Interfacial Electrochemistry for Energy Materials (CIE2M) grant DMR-1827622.