Hierarchical Co(OH)2 Dendrite Enriched with Oxygen Vacancies for Promoted Electrocatalytic Oxygen Evolution Reaction

Abstract

It is critical to develop efficient oxygen evolution reaction (OER) catalysts with high catalytic properties for overall water splitting. Electrocatalysts with enriched vacancies are crucial for enhancing the catalytic activity of OER through defect engineering. We demonstrated the dealloying method in a reducing alkaline solution using the Co5Al95 alloy foil as a precursor to produce a new oxygen-vacancy-rich cobalt hydroxide (OV−Co(OH)2) hierarchical dendrite. The as-synthesised OV−Co(OH)2 showed superior electrocatalytic activities toward OER when compared to pristine cobalt hydroxide (p–Co(OH)2), which had a low onset overpotential of only 242 mV and a small Tafel slope of 64.9 mV dec−1. Additionally, for the high surface area provided by the hierarchical dendrite, both p–Co(OH)2 and OV−Co(OH)2 showed a superior activity as compared to commercial catalysts. Furthermore, they retained good catalytic properties without remarkably decaying at an overpotential of 350 mV for 12 h. The as-made OV−Co(OH)2 has prospective applications as an anode electrocatalyst in electrochemical water-splitting technologies with the advantages of superior OER performances, large surface area and ease of preparation.

Two-Dimensional Hierarchical CoTe/NiFe Layered Double Hydroxide Heterostructure for High-Performance Electrocatalytic Water Oxidation

“… − This is consistent with the lattice fringe of post-OER CoTe NS/NiFe LDH obtained through HR-TEM, suggesting that the Co and Fe elements are oxidized during the water oxidation. Co 3 O 4 and Fe 3 O 4 observed in post-OER CoTe NS/NiFe LDH can be formed through the following phase transition process − normalC normalo + 2 normalO normalH − → normalC normalo ( O H ) 2 + 2 normale − normalC normalo ( O H ) 2 + normalO normalH − → normalC normalo normalO normalO normalH + normalH 2 normalO + normale − 3 normalC normalo normalO normalO normalH + normale − → normalC normalo 3 normalO 4 + normalH 2 normalO + normalO normalH − normalF normale ( O H ) 2 + normal...…”

“… − This is consistent with the lattice fringe of post-OER CoTe NS/NiFe LDH obtained through HR-TEM, suggesting that the Co and Fe elements are oxidized during the water oxidation. Co 3 O 4 and Fe 3 O 4 observed in post-OER CoTe NS/NiFe LDH can be formed through the following phase transition process − …”

Dealloying fabrication of hierarchical porous Nickel–Iron foams for efficient oxygen evolution reaction

“…Additionally, it is worth noting that Figure 3E shows an unusual change in the condition of oxygen. Oxides (529.8 eV) and Ov (530.3 eV) appear ( Nai et al, 2013 ; Lv et al, 2021 ; Zhou et al, 2022 ). After the active metal ions have been dissolved during the dealloying process, the oxidation conditions may not be able to reach the interior of the material.…”