Convenient Immobilization of Cobalt Corroles on Carbon Nanotubes through Covalent Bonds for Electrocatalytic Hydrogen and Oxygen Evolution Reactions

Abstract

Twod ifferentm ethods were used to immobilize Co corroles on carbon nanotubes (CNTs) through covalent bonds. The resulting CNTse ngineered with Co corroles were used as electrocatalysts for the hydrogen evolutionr eaction (HER) and the oxygen evolution reaction (OER) in aqueous solutions of pH 0, 7, and 14. For both HER andO ER in all solutions, the hybrids obtained by attaching Co corroles on CNTst hrough amidation coupling showedb etter performance. This is likely because the large surface area and good electricalc onductivity of CNTsc an be well preserved during the amidationr eactionu nder mild conditions.The development of inexpensive, efficient, and robust electrocatalysts for the hydrogen evolutionr eaction (HER) and the oxygen evolution reaction( OER) has attracted increasing interest because of their appealing applicationsi nn ew energy technologies. [1][2][3] During the last decade,avariety of molecular complexes based on earth-abundant transition-metal elements including Mn, [4][5][6][7] Fe, [8][9][10][11][12][13][14] Co, [15][16][17][18][19][20][21] Ni, [22][23][24][25][26][27][28] and Cu [29][30][31][32][33] have been identified as catalystsf or these two reactions. To make these well-designed molecular catalysts useful in practice, they need to be immobilizedo ne lectrode materials. [34][35][36][37][38] Covalent immobilizationi su seful to improvec atalyst stabilitya nd performance and benefitst he recycling of electrocatalysts. [39][40][41][42][43] Despite these progresses,h owever, convenient methods for covalenti mmobilization under mild conditions are still needed.Carbon nanotubes (CNTs) are broadly used as supports for electrochemical applications because of their large surface areas and good electrical conductivities. [37,[44][45][46][47][48][49] Thep resence of abundant carboxyl groups on the surface of oxidized CNTsprovides ideal sites to attach catalystm olecules bearing amine groups through the amidation reaction. The resulting amide bonds tolerateb oth acidic and basic media and have sufficient stabilityu nder reductive and oxidative conditions. These features make CNTsp romising electrode materials for molecular engineering. However, the direct reaction of carboxyl and amine groupst of orm amide bonds is challenging. Therefore, carboxyl groups are usually converted to acyl chloride groups for subsequent amidation reaction.Herein, we report the convenient immobilization of Co corroles on CNTst hrough amidation coupling under mild conditions. Co corroles have been shown to be highly active and stable as catalysts for HERa nd OER under various conditions, [3,19] andt hust hey were chosen as model complexes in this work. The resulting hybrid can catalyze both HER and OER in aqueous solutionso fp H0,7 ,a nd 14. Compared with the traditional amidation by activating carboxyl groups with sulfinyl dichloride (SOCl 2 ), the directa midation coupling is simpler and more straightforward, and the resulting hybrid shows much better performance. This work is significant to showt he importance of the co...

Electrocatalytic Hydrogen Evolution of Cobalt and Free‐base Triaryl Corrole Bearing Hydroxyethyl Amino Groups

“…The best electrocatalytic activity for HER is realized via anchoring strong electron‐deficient substituents in all meso‐position of corrole ligand . It is also observed that other metal corroles such as cobalt 5,10,15‐tris‐(nitrophenyl)corrole, cobalt tris‐(ethoxycarbonyl)corrole, cobalt 5,15‐bis(4‐aminophenyl)‐10‐(pentafluorophenyl)corrole, as well as the metal complexes of other corroles bearing ‐NO 2 , ‐N 3 , ‐NH 2 , pyrenyl are also efficient electrocatalysts for HER. As compared to substitution on meso‐phenyl of corrole, β ‐substitution has more substantial influence on electrochemical properties of metal corrole.…”

Catalysis of a Single Transition Metal Site for Water Oxidation: From Mononuclear Molecules to Single Atoms

“…To enable the firm immobilization of SMMCs through covalent linkage, delicate surface functionalization of the ligand or the support with additional organic anchor groups (e.g., pyrene, OH, SH, NH 2 , COOH) is pivotal . These groups also afford a good control over the density and orientation of SMMCs on the support surface .…”

Mono‐/Multinuclear Water Oxidation Catalysts

“…[152] They analyzed OÀOb ond formation for eight TM hangmanc orroles and found that Co V had the lowest energy barrierf or OÀOb ond formation, which indicated that the cobalt hangmanc orrole had the highest activity. [157] Cao and co-workersa lso found that ap yrene-modifiedC o-corrole supported on multiwalled carbon nanotubes (MWCNTs) exhibited high OER activity and strong stability;t he high activity was attributed to strongn oncovalent p-p interactions between the pyrene and MWCNTs. [153] The OER mechanism involved the PCET process and the energy barrierf or OÀOb ond formation was 18.1 kcal mol À1 ,a sd etermined by theoretical calculations, which was consistent with the estimated value obtained from experiments (about 18.5 kcal mol À1 ).…”

“…[156] Direct amidation coupling has provedt ob eas imple way to immobilize Co-corroles on CNTs, and would be ap romising prospecti no ther electrocatalytic applications. [157] Cao and co-workersa lso found that ap yrene-modifiedC o-corrole supported on multiwalled carbon nanotubes (MWCNTs) exhibited high OER activity and strong stability;t he high activity was attributed to strongn oncovalent p-p interactions between the pyrene and MWCNTs. [158] Additionally,m ononuclearc obalt complexes with Py5-based ligands( Py5: 2,6-[bis(bis-2-pyridyl)methoxymethane]pyridine) have been synthesized.…”