A Thiadiazole-Based Covalent Organic Framework: A Metal-Free Electrocatalyst toward Oxygen Evolution Reaction

Abstract

Covalent organic frameworks (COFs) have attracted surging interest lately due to their wide potential in several frontline application areas like gas storage, sensing, photovoltaics, fuel cells, active catalyst supports, and so on. However, only very few reports are available for the metal-free electrocatalysis over COFs. Herein, we developed a new thiadiazole-based COF, C4-SHz COF, through the reaction between 1,3,5-tris(4-formylphenyl)benzene and 2,5-dihydrazinyl-1,3,4-thiadiazole that possesses a very high specific surface area of 1224 m 2 g −1 , unique molecular architecture, high porosity, and abundant active sites. The as-synthesized C4-SHz COF displayed superior electrocatalytic oxygen evolution reaction (OER) activity and excellent long-term durability. The electrocatalytic performance of the C4-SHz COF achieved a current density of 10 mA/cm 2 at an overpotential of 320 mV. The higher activity of the C4-SHz COF could be attributed to the high Brunauer−Emmett−Teller surface area, porosity, and network structure of the π-conjugated organic building blocks, which allowed fast charge and mass transport processes. This work validates the promising potential of a metal-free COF electrocatalyst toward the OER and its capability to replace carbon-based electrocatalysts.

Activation of Carbonyl Oxygen Sites in β‐Ketoenamine‐Linked Covalent Organic Frameworks via Cyano Conjugation for Efficient Photocatalytic Hydrogen Evolution

“…[ 25 ] Especially, Tp‐DBN shows the peak near 95 ppm, corresponding to the CN triple bonds. [ 26 ] Indeed, no peaks at ≈165 ppm (for CN) [ 20 ] and ≈190 ppm (for CHO) [ 13a,19b ] could be observed for the other starting materials of Tp, implying the complete consumption of Tp and irreversible isomerization into the keto forms (i.e., Tp‐PDA and Tp‐DBN) instead of their enol forms.…”

“…[ 9 ] The charming tuneable topology structures endow COFs with unique characteristics of porous structures, abundant surface active sites, and superior charge separation/migration for exclusive applications, including energy transfer, [ 10 ] optoelectronics, [ 11 ] biomedical, [ 12 ] and catalysis. [ 13 ] Since the pioneering report by Lotsch et al. in 2014, [ 14 ] the impressive capacity for photocatalytic HER has been drawing wide and intense attention in designing specific COFs with high crystallinity, favorable surface hydrophilicity, suitable bandgap structure, and excellent chemical/thermal stability.…”

Covalent Organic Frameworks for Efficient Energy Electrocatalysis: Rational Design and Progress

“…Furthermore, Bhaumik and coworkers reported a new thiadiazole‐based COF, termed C4‐SHz COF, through the Schiff‐base condensation reaction between 1,3,5‐tris(4‐formylphenyl)benzene (C4‐CHO) and 2,5‐dihydrazinyl‐1,3,4‐thiadiazole (SHz), as shown in Figure 9e. [ 75 ] Through activation by the supercritical carbon dioxide treatment, the as‐synthesized C4‐SHz COF material showed the well‐defined stacked framework (Figure 9f) and possessed superior properties such as a high specific surface area of 1224 m 2 g −1 , high porosity, and abundant active sites. When used as a metal‐free OER electrocatalyst, the C4‐SHz COF catalyst displayed outstanding OER activity and long‐term durability, such as a low onset potential of 270 mV, a low overpotential of 320 mV at the current density of 10 mA cm −2 (Figure 9g), and a Tafel slope of 39 mV dec −1 (Figure 9h).…”

Heterostructure and Oxygen Vacancies Promote NiFe2O4/Ni3S4 toward Oxygen Evolution Reaction and Zn‐Air Batteries

“…[5,6] Unfortunately, the practical performance of both rechargeable zinc air batteries and electrochemical water splitting device is significantly hindered by the key electrochemical process namely oxygen evolution reaction (OER) occurring at the electrode, as an energy barrier needs to be overcome in OER to accomplish the 4-electron transfer process and forming the covalent OÀ O bond. [7][8][9][10] To that end, developing high-performance OER electrocatalysts is imperative to realize clean energy storage through the two above sustainable pathways.…”

“…Rechargeable zinc air batteries (ZABs) hold the great advantages including high theoretical energy density, low cost, environmental friendliness, and intrinsic safety nature, [3,4] while electrochemical water splitting into H 2 and O 2 has been widely regarded as one of the most promising strategies to effectively use renewable energy from harvest to redistribution [5,6] . Unfortunately, the practical performance of both rechargeable zinc air batteries and electrochemical water splitting device is significantly hindered by the key electrochemical process namely oxygen evolution reaction (OER) occurring at the electrode, as an energy barrier needs to be overcome in OER to accomplish the 4‐electron transfer process and forming the covalent O−O bond [7–10] . To that end, developing high‐performance OER electrocatalysts is imperative to realize clean energy storage through the two above sustainable pathways.…”