A Self‐Reconstructed Bifunctional Electrocatalyst of Pseudo‐Amorphous Nickel Carbide @ Iron Oxide Network for Seawater Splitting. Issue 15 (25th March 2022)

• Record Type: Journal Article
• Authors: Zhang, Hao; Geng, Songyuan; Ouyang, Mengzheng; Yadegari, Hossein; Xie, Fang; Riley, D. Jason
• Is Part Of: Advanced science. Volume 9:Issue 15(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-03-25
• Subjects: iron oxide -- lattice oxygen -- nickel carbide -- seawater splitting -- self‐reconstruction; Science -- Periodicals; 505
• DOI: 10.1002/advs.202200146
• Languages: English
• ISSNs: 2198-3844

Abstract

Abstract: Here, a sol‐gel method is used to prepare a Prussian blue analogue (NiFe‐PBA) precursor with a 2D network, which is further annealed to an Fe3 O4 /NiCx composite (NiFe‐PBA‐gel‐cal), inheriting the ultrahigh specific surface area of the parent structure. When the composite is used as both anode and cathode catalyst for overall water splitting, it requires low voltages of 1.57 and 1.66 V to provide a current density of 100 mA cm −2 in alkaline freshwater and simulated seawater, respectively, exhibiting no obvious attenuation over a 50 h test. Operando Raman spectroscopy and X‐ray photoelectron spectroscopy indicate that NiOOH2–x active species containing high‐valence Ni 3+ /Ni 4+ are in situ generated from NiCx during the water oxidation. Density functional theory calculations combined with ligand field theory reveal that the role of high valence states of Ni is to trigger the production of localized O 2p electron holes, acting as electrophilic centers for the activation of redox reactions for oxygen evolution reaction. After hydrogen evolution reaction, a series of ex situ and in situ investigations indicate the reduction from Fe 3+ to Fe 2+ and the evolution of Ni(OH)2 are the origin of the high activity. Abstract : An Fe3 O4 /NiCx composite (NiFe‐PBA‐gel‐cal) with ultrahigh specific surface area was prepared, and it exhibits excellent seawater splitting performance. The in situ generated NiOOH2–x trigger the production of O 2p electron holes for the acceleration of oxygen evolution reaction, and the reduction from Fe 3+ to Fe 2+ and the evolution of Ni(OH)2 are the origin of high activities of hydrogen evolution reaction.