Activating Co(OH)₂ Active Sites by Coupled with V₂O₅ to Boost Highly Efficient Oxygen Evolution Reaction

Abstract

Electrocatalytic water splitting generated oxygen (O2) and hydrogen (H2) is a promising way to solve the energy crisis. Oxygen evolution reaction (OER) compared to hydrogen evolution reaction (HER) has slow kinetics hindering overall process. Recently, cobalt hydroxide (Co(OH)2) with high activity and stability for OER has attracted more attention. During the OER process, the Co2+ in Co(OH)2 is further oxidized to Co3+ and CoOOH species are true active sites. However, the low conductivity of Co(OH)2 hinders its oxidization to CoOOH. In addition, spontaneous growth of Co(OH)2 agglomerates easily during hydrothermal treatment, leading to decreased active sites. Herein, an efficient strategy is developed to construct highly dispersive Co(OH)2 nanosheets vertically grown on V2O5 nanoflowers (Co(OH)2/V2O5) at room temperature. The V5+ of V2O5 can oxidize Co2+ of Co(OH)2 into Co3+, resulting in in situ formations of CoOOH species favorable to the OER process. In situ Raman also investigates that the OH‐ species are inserted more easily into the interlayer of Co(OH)2 of (Co(OH)2/V2O5) than that of pure Co(OH)2. Therefore, the hybrid Co(OH)2/V2O5 exhibits low overpotentials of 320 and 370 mV at a current density of 10 and 50 mV cm‐2, respectively, and a small Tafel slope of 68 mV dec‐1.

N-Doped C Concatenates FeCo Alloys and Co Nanoparticles as a Dual-Functional Oxygen Catalyst for Long-Lasting Zinc–Air Batteries

“…The distance between Co NPs and FeCo alloys is about 19 nm according to the HRTEM image, while the optimal range for synergy between the adjacent active sites is about 0.5 nm . The separate active sites availably prevent the oxidation of the ORR catalytic active sites by the *OH intermediates generated during the OER. , …”

“…48 The separate active sites availably prevent the oxidation of the ORR catalytic active sites by the *OH intermediates generated during the OER. 49,50 The partial reconstruction of FeCo AL &Co NP /NC after operating for 13 h was ulteriorly testified via infrared (IR) spectroscopy (Figure 4c). At the initial state, FeCo AL &Co NP / NC exhibited two obvious peaks at 1051 and 1130 cm −1 , attributed to the functional groups present in the carbon materials.…”

Constructing Ag Single Atoms and Nanoparticles Co‐Decorated CoO(O)H as Highly Active Electrocatalyst for Oxygen Evolution Reaction under Large Current Density

“…Besides, the Co 2p spectra for all samples manifest that the valence state of Co is a hybrid of +2 and +3 (Figure 2b). [43,44] With the increase of the Ag content, the Co 3+ /Co 2+ ratio gradually decreases. Meanwhile, the average valence state of Co in different samples increases in the following order of CoO(O)H < Ag NPs@CoO(O)H < Ag SAs&NPs@CoO(O)H < Ag SAs@CoO(O)H. This suggests that the silver content has an effect on the proportion of CoOOH in CoO(O)H. In addition, the O 1s spectra of the CoO(O)H reveal the existence of hydroxide species and adsorbed water molecules, as manifested by the two peaks observed at 531.2 and 532.7 eV, respectively (Figure 2c).…”

Substantial Electrocatalytic Oxygen Evolution Performances of Activated Carbon-Decorated Vanadium Pentoxide Nanocomposites

“…International Journal of Energy Research clearly revealed the linear features at the low frequency region, attributing to the electrolyte diffusion within the catalyst medium [10,15]. At the high frequency region, however, the samples exhibited no clear semicircles but revealed only small parabolic curvatures, which are associated with the charge transfer resistance (R ct ) [70]. By calculating the R s and R ct values using an equivalent circuit model (Figure 7, insets), it was found out that, compared to V 2 O 5 (R s : 0.86 Ω, R ct : 83 mΩ), AC-V 2 O 5 has smaller resistance values (R s : 0.84 Ω, R ct : 51mΩ; see also Table S1).…”