Defect‐Driven Enhancement of Electrochemical Oxygen Evolution on Fe–Co–Al Ternary Hydroxides

Abstract

Efficient, abundant and low‐cost catalysts for the oxygen evolution reaction (OER) are required for energy conversion and storage. In this study, a doping–etching route has been developed to access defect rich Fe–Co–Al (Fe–Co–Al‐AE) ternary hydroxide nanosheets for superior electrochemical oxygen evolution. After partial etching of Al, ultrathin Fe3Co2Al2‐AE electrocatalysts with a rich pore structure are obtained with a shift of the cobalt valence state towards higher valence (Co2+→Co3+), along with a substantial improvement in the catalytic performance. Fe3Co2Al2‐AE shows a notably lower overpotential of only 284 mV at a current density of 10 mA cm−2 and double the OER mass activity of the etching‐free Fe3Co2Al2 with an overpotential of 350 mV. Density functional theory shows the leaching of Al changes the rate‐determining step of the OER from conversion of *OOH into O2 on Fe3Co2Al2 to formation of OOH from *O on the Al‐defective catalysts. This work demonstrates an effective route to design and synthesize transition metal electrocatalysts and provides a promising alternative for the further development of oxygen evolution catalysts.

Design and operando/in situ characterization of precious‐metal‐free electrocatalysts for alkaline water splitting

“…Moreover, incorporating less stable elements such as Al and Zn cation as a sacrificial agent can create surface defects with the exposure of more low-coordinated metal sites by selective removal of the dopants, which in turn improves the catalytic performance. 100,149,161 The enhanced HER activity can also be achieved by metal doping because of the enhanced electron interactions and optimal ΔG H* during HER process. 59,62,162 For example, 3D hierarchical Cudoped porous Ni catalyst (Ni(Cu)/NF) exhibited satisfying catalytic activity toward HER because of the lattice distortion of Ni and the formation of NiO/Ni with increased interfacial activities.…”

“…The incorporation of heteroatom dopants can synergistically modulate the electronic structure of NiO, generate unsaturated surface Ni 3+ and Mn 3+ active sites and oxygen vacancies, which was found to be critical for promoting the OER performance. Moreover, incorporating less stable elements such as Al and Zn cation as a sacrificial agent can create surface defects with the exposure of more low‐coordinated metal sites by selective removal of the dopants, which in turn improves the catalytic performance 100,149,161 . The enhanced HER activity can also be achieved by metal doping because of the enhanced electron interactions and optimal ΔG H* during HER process 59,62,162 .…”

Harnessing the Synergistic Interplay of Fischer‐Tropsch Synthesis (Fe‐Co) Bimetallic Oxides in Na‐FeMnCo/HZSM‐5 Composite Catalyst for Syngas Conversion to Aromatic Hydrocarbons

“…The disordered occupation of multivalent cations at the octahedron and tetrahedron sites in the spinel crystal can induce the distortion of lattice structure, which can promote the unbalanced bonding state of the oxygen atom being located at the surface. [26] As a result, the oxygen atom prone to separation can facilitate the formation of high-density oxygen vacancies on the exposed surface of the spinel in response to the lattice distortion. Therefore, it can be inferred that the synergistic interactions between different metals being doped in particular calcination temperature, could enhance the surface energy of exposed planes and facilitate the lattice defects which in turn promote the generation of oxygen vacancies.…”

Defective NiFe2O4 Nanoparticles for Efficient Urea Electro‐oxidation

“…In order to prepare high‐performance urea electro‐oxidation catalysts, many methods have been developed, including preparing 2D nanosheets, synthesizing heterostructures, and growing on conductive substrates . In recent years, defect engineering strategy was widely adopted for optimizing the catalytic property of various catalysts in many areas, including photocatalytic hydrogen evolution and electrocatalytic hydrogen evolution, oxygen evolution as well as oxygen reduction . Actually, significantly enhanced catalytic performances were found by researchers mainly owing to the increased numbers of active sites .…”