Improved Catalytic Activity and Stability of Co₉S₈ by Se Incorporation for Efficient Oxygen Evolution Reaction

Abstract

Combining an excellent electrocatalytic activity with the good structural stability of Co9S8 remains challenging for the oxygen evolution reaction (OER). In this study, density functional theory was used to demonstrate the importance of moderate adsorption strength with *O and *OOH intermediate species on Co9S8 for achieving excellent electrocatalytic performances. A novel strategy was proposed to effectively optimize the *O oxidation to *OOH by introducing Se heteroatoms to adjust adsorption of the two intermediates. This process also allowed prediction of the simultaneous enhancement of the structural stability of Co9S8 due to the weak electronegativity of a Se dopant. The experimental results demonstrated that Se doping can regulate the charge density of Co2+ and Co3+ in Co9S8–x Se x , leading to a substantially improved OER performance of Co9S8–x Se x . As a result, our Co9S6.91Se1.09 electrode exhibited an overpotential of 271 mV at 10 mA cm–2 in a 1.0 M KOH solution. In particular, it also demonstrated an excellent stability (∼120 h) under a current density of 10 mA cm–2, indicating the potential for practical applications. Overall, the proposed strategy looks promising for regulating the electronic structures and improving the electrochemical performances of sulfide materials.

Synthesis of Co9S8nanoflakes by a one-step solvent-free solid-state method for multiple electrocatalytic reactions

“…It should be noted that S-Co 9 S 8 possesses a higher proportion of Co 2+ /Co 3+ , which is beneficial for the formation of a true active phase during the electrochemical OER processes and can effectively improve the OER performance. 35 In the high-resolution S 2p spectra, both S-Co 9 S 8 and H-Co 9 S 8 represent the characteristic peaks of Co–S at about 161.71 and 162.80 eV. Additionally, the peak at the 164.2 eV can be assigned to the surface sulfide ions of the materials, and the existence of SO 4 2− indicated that they were partly oxidized by air.…”

Simultaneously Improving Energy Storage and Oxygen Evolution Reaction by Causing Regional Defects in MOF-on-MOF Derived Hollow Se-Doped CoP-Fe2P Heterojunctions

“…17 found that the doping of Se could reduce the energy barrier for the rate-determining step in the OER process, which promotes the adsorption of *OOH and improves the electrocatalytic activity for water splitting. 18 On the other hand, vacancy defects have also been proven to be an effective method for altering interfacial chemical properties and exposing active sites. 19,20 Qian et al combined heterostructure engineering and vacancy strategies to fabricate a CoP v -Mo x P v /CNT electrocatalyst enriched with P defects and indicated that P vacancies can promote reaction kinetics and generate more active sites, ultimately displaying an overpotential of only 138 mV at 10 mA cm −2 for HER in 0.5 M H 2 SO 4 .…”

“…For instance, Yang et al employed both heteroatom doping and heterostructure engineering to prepare W-CoP/FeP nanoparticles and revealed that W-doping provides additional active sites, accelerates electron transfer rates, and enhances the synergistic effect between CoP and FeP . Wang et al prepared Se-doped Co 9 S 8 electrodes and found that the doping of Se could reduce the energy barrier for the rate-determining step in the OER process, which promotes the adsorption of *OOH and improves the electrocatalytic activity for water splitting …”

Research progress on hydroxide fluoride-based electrode materials for supercapacitors

“…However, these energy sources are intermittent in their availability. To ensure a continuous energy supply, there is an urgent need to develop efficient energy storage devices [4,5] . Supercapacitors have the potential to serve as an alternative electrochemical energy storage technology, replacing widely commercialized rechargeable batteries [3,6,7] .…”