Phosphate Ion‐Functionalized CoS with Hexagonal Bipyramid Structures from a Metal–Organic Framework: Bifunctionality towards Supercapacitors and Oxygen Evolution Reaction

Abstract

To solve energy-related environmental problems and the energy crisis, efficient electrochemical materials have been developed as alternative energy storage and conversion systems. Abundant transition metalsa nd their sulfides are attractive electrochemical materials. Herein, we report an efficient phosphorization strategy,w hich improves the overall electrochemical performance of metal sulfides. In detail, CoS hexagonal bipyramids were synthesized through simple calcination combined with in situ sulfurizationo fa cobalt-based metal-organic framework template, and then phosphate ion-functionalized CoS (P-CoS)w as prepared through ap hosphorization reaction.P-CoS exhibited outstandinge lectrochemical activity as both supercapacitor electrode and oxygene volution reaction (OER) catalyst. Supercapacitors based on CoS and P-CoS as the electrodes had high specific capacitances of 304 and 442 Fg À1 ,r espectively, and remaineds table for over 10 000 cycles at 5Ag À1 .F or OER, P-CoS showed ac urrent density of 10 mA cm À2 at an overpotentialo f3 40 mV,w ith as mall Ta fel slope. In conclusion, functionalizing CoS with phosphate ions is ap romising method fore nhancing chemical reactivity and accelerating ion and electront ransfer.

Experimental and Theoretical Insights of Anion Regulation in MOF-Derived Ni–Co-Based Nanosheets for Supercapacitors and Anion Exchange Membrane Water Electrolyzers

“…16 However, the wholesale application of Ir and Ru-based TMOs is considerably hindered by their exorbitant costs, harmful effects on the environment, limited availability, and inferior durability. 13,17,18 catalysts. Among different electrolysis assemblies (alkaline water electrolysis (AWE) and proton exchange membrane water electrolysis (PEMWE)), the anion exchange membrane (AEM) water electrolyzer exhibits the immense capability for producing highly pure hydrogen at a reasonable price using an anion exchange membrane as a solid polymer-based electrolyte.…”

“…For instance, Ding et al studied the anion-dependent EWS characteristics of nickel foam (NF)-supported Zn–Ni–Co–M nanoneedle arrays (where M = oxide (O), P, S, and Se) and observed that Zn–Ni–Co–P and Zn–Ni–Co–S achieved the lowest overpotential values for the HER and OER, respectively . Jiang et al prepared phosphate ion-incorporated CoS to improve the supercapacitive and OER performance of CoS . Guo et al reported a dual-ligand synergetic modulation method to boost the energy storage performance of Ni–Co–A (where A = Se, P, and S) by partially doping Se, P, and S in Ni–Co hydroxide precursor arrays .…”

“…Generally, the incorporation of different non-metal/ anionic ligands (Se, S, and P anions) into a mixed TM-based matrix can alter the electrochemically active sites and the density of defective sites by adjusting the electronic structure, thereby modulating electrochemical properties. 16 Jiang et al prepared phosphate ion-incorporated CoS to improve the supercapacitive and OER performance of CoS. 18 Guo et al reported a dual-ligand synergetic modulation method to boost the energy storage performance of Ni− Co−A (where A = Se, P, and S) by partially doping Se, P, and S in Ni−Co hydroxide precursor arrays. 36 Fang et al prepared Se-doped CoS (Co(S x Se 1−x ) 2 ) and reported that Co-(S 0.71 Se 0.29 ) 2 achieved the best activity for the HER, and Co(S 0.22 Se 0.78 ) 2 exhibited a higher OER activity in a basic medium than the pure CoSe 2 and CoS 2 .…”

“…The state-of-the-art precious iridium (Ir) and ruthenium (Ru)-based transition metal oxides (TMOs) are employed as suitable electrocatalysts for accelerating the OER process . However, the wholesale application of Ir and Ru-based TMOs is considerably hindered by their exorbitant costs, harmful effects on the environment, limited availability, and inferior durability. ,, Hence, the advanced earth-abundant TM-based electrocatalysts are requisite for the OER to substitute precious metal-based catalysts. Among different electrolysis assemblies (alkaline water electrolysis (AWE) and proton exchange membrane water electrolysis (PEMWE)), the anion exchange membrane (AEM) water electrolyzer exhibits the immense capability for producing highly pure hydrogen at a reasonable price using an anion exchange membrane as a solid polymer-based electrolyte. − In principle, the AEM water electrolyzer permits the use of hardware and cost-effective (nonprecious) metal catalysts as that of AWE as well as it can deliver high-purity H 2 at a comparable current level and safety as that of PEMWE.…”

CoS2 Nanoparticles Embedded in Covalent Organic Polymers as Efficient Electrocatalyst for Oxygen Evolution Reaction with Ultralow Overpotential

“…CoS 2 @BP‐COP affords the highest catalytic activity with an ultralow overpotential of 270 mV to deliver a current density of 10 mA cm −2 (Figure 4b). This value is much lower than that of the as‐prepared CoS 2 (319 mV), commercially available RuO 2 (351 mV), vulcanized BP‐COP (BP‐COP‐S, 432 mV), and nickel foam (NF) current collector (487 mV), and other reported cobalt sulfides based electrocatalysts (normally 285∼340 mV) [3a,8a,9b,d] . Tafel slopes were calculated based on LSV to study the reaction kinetics of corresponding electrocatalysts for OER.…”