Molten-Salt-Protected Pyrolytic Approach for Fabricating Borate-Modified Cobalt–Iron Spinel Oxide with Robust Oxygen-Evolving Performance

Abstract

Oxygen evolution reaction (OER) holds tremendous attention owing to its critical role as the rate-limiting half reaction of the electrochemical water splitting for hydrogen production. Hence, discovering facile routes to fabricate the earth-abundant OER catalysts with high activity and durability is of great importance to realize commercial water splitting. Herein, a modified molten-salt-protected pyrolysis (MSPP) approach was proposed, which leads to simultaneous fabrication of cobalt–iron spinel oxide nanoassembly and borate modification on the surface of the catalyst. Physical characterizations indicated that both the MSPP method and the surface borates could optimize the electronic structure of CoFe spinel oxide, leading to the enrichment of local high-valence metal species with enhanced electropositivity and thus resulting in improved intrinsic activity toward OER catalysis. Besides, due to multiple structural merits including a large surface area, enriched high-valence metal sites, improved intrinsic activity, and facilitated charge transfer behavior, the borate-modified CoFe spinel oxide catalyst synthesized via the MSPP route exhibits outstanding OER activity with low overpotential, large current density, and small Tafel slope. In addition, the activation process was confirmed during long-term catalysis, resulting in a remarkable 140% performance enhancement with high operational stability even for 72 h. This work proposed a modified molten-salt synthesis strategy to achieve synergistic enrichment of catalytically active species and surface modification, and the as-fabricated borate-modified CoFe spinel oxide could act as an efficient and durable OER catalyst for robust water electrolysis.

Cerium-induced lattice disordering in Co-based nanocatalysts promoting the hydrazine electro-oxidation behavior

“…3B, the post-catalytic TEM image of 1%Ce:Co-N-C reveals negligible changes in morphology, which Besides, a newly formed peak at 535.6 eV can be detected, indicating the generation of peroxide intermediates stabilized by the active Co species during the electro-oxidation. [29][30][31] In summary, Ce-incorporated Co-based catalysts embedded in N-doped carbon were fabricated for the hydrazine electrooxidation reaction. The Ce incorporation could lead to the formation of surface oxide nanolayers with a disordered lattice, resulting in enriched undercoordinated active sites and optimal electronic structure for the HzOR.…”

“…Besides, a newly formed peak at 535.6 eV can be detected, indicating the generation of peroxide intermediates stabilized by the active Co species during the electro-oxidation. 29–31…”

Dual Promoting Effects of Hereditary Mn Doping and Oxygen Vacancies on Porous CuCo2O4 for Electrocatalytic Oxygen Generation

“…The LSV curves with iR compensation in Figure a reveal that O V -np-Cu 10 Co 20 (Mn) requires an overpotential of only 310 mV to reach 10 mA cm –2 (η 10 ), which is much lower than those of O-np-Cu 10 Co 20 (Mn) (450 mV), O-np-Co 30 (Mn) (520 mV), O-np-Cu 30 (Mn) (690 mV), O V -np-Co 30 (Mn) (380 mV), O V -np-Cu 30 (Mn) (670 mV), RuO 2 (340 mV), and some other reported OER catalysts (Figure c and Table S2). − It reflects that O V could really dramatically reduce the overpotential of OER. Furthermore, although O V -np-Co 30 (Mn) or O-np-Co 30 (Mn) has no abundant porous structures, it is more active toward OER than inert O V -np-Cu 30 (Mn) or O-np-Cu 30 (Mn).…”

Modulating the electronic configuration of Co species in MOF/MXene nanosheet derived Co-based mixed spinel oxides for an efficient oxygen evolution reaction

“…5 In virtue of low cost, environmental friendliness, and ready tunability, cobalt-based spinel oxides have been widely studied as substitutes for noble metal-based electrocatalysts for the OER. [6][7][8][9] They can be described as AB 2 O 4 , where oxygen anions are arranged in a cubic close-packed lattice with metal ions located in tetrahedral (Td) and octahedral (Oct) interstices. 10 A general principle demonstrates that the redox activity of Co cations in Oct sites is crucial for the OER process.…”