Electrochemical Reconstruction of Zn_0.3Co_2.7(PO₄)₂·4H₂O for Enhanced Water Oxidation Performance

Abstract

Developing electrocatalysts with abundant active sites is a substantial challenge to reduce the overpotentials for the water splitting reaction. Toward the oxygen evolution reaction (OER) in alkaline medium, designing precatalysts that could provide abundant catalytic active centers can significantly improve the electrocatalytic activity. This work demonstrates the production of active α-Co(OH) 2 /CoOOH species using the sacrificial pre-catalyst Zn x /Co 3−x (PO 4 ) 2 •4H 2 O (ZCP) (x = 0.15−0.9), which was developed by the one-step hydrothermal method. Electrochemical activation of ZCP results in the formation of a porous cobalt catalyst with abundant active centers. Elemental analysis revealed that both Zn 2+ and PO 4 3− ions etch away during the activation process, thereby exposing a higher number of catalytically active cobalt centers that otherwise stay inactive due to their location in the bulk. The resulting materials showed promising electrocatalytic activities toward OER; especially, a material (ZCP-0.3) consisting of Zn 2+ and Co 2+ in a 1:7 ratio was found to deliver the best activity. The carbon paper-supported ZCP-0.3 exhibited a high current density of 50 mA/cm 2 at an overpotential of 390 mV. In contrast, the material prepared without zinc (i.e., Co 3 (OH) 2 (HPO 4 ) 2 ) showed inferior catalytic activity, thus demonstrating the necessity for Zn 2+ etching to expose the additional active sites for improved electrocatalytic activity of ZCP-0.3.

Hydrovoltaic power generation from multiwalled carbon nanotubes

“…R CT values have an inverse relationship with power output because higher resistance to the charge transfer process inhibits the ow of charge carriers, lowering HV activity. 26,27 The resistance decreases up to 6 mg and then increases, indicating faster charge transfer kinetics at 6 mg for the 3 cm  1.5 cm size. With loading masses above 6 mg the lm loses its stability in water, conrming optimal lm formation at 6 mg for 3 cm  1.5 cm.…”

Influence of Vanadate Structure on Electrochemical Surface Reconstruction and OER Performance of CoV2O6 and Co3V2O8

“…Recently, few research groups including ourselves have reported that electrochemical surface reconstruction due to etching of a constituent from an electrocatalyst often turns out to be beneficial for electrocatalytic activity . The etching process exposes a higher number of catalytic centers that otherwise lay inactive due to their position in the bulk, to the electrolyte . In this article, a similar trend was observed; i.e., with increased vanadate etching, the activity steadily increased.…”

“…21 The etching process exposes a higher number of catalytic centers that otherwise lay inactive due to their position in the bulk, to the electrolyte. 22 In this article, a similar trend was observed; i.e., with increased vanadate etching, the activity steadily increased. We believe that, due to the polymeric structure of metavanadate, its etching from the material would tear off a long chain of vanadate thereby aiding the transformation of the material to its active phase.…”

In situ formation of Co3O4 nanocrystals embedded in laser-induced graphene foam for high-energy flexible micro-supercapacitors

“…4b, the even distribution of the elements only including carbon, oxygen and cobalt elements, suggests that the Co spin-orbit peaks, respectively. 26,27 Two shakeup satellite (labeled as "Sat.") peaks (at 790.2 and 805.1 eV) can also be observed in the XPS spectra of the Co 3 O 4 @LIG nanocomposite, which is in good agreement with the previous reports.…”