Morphology Tuning via Linker Modulation: Metal‐Free Covalent Organic Nanostructures with Exceptional Chemical Stability for Electrocatalytic Water Splitting

Abstract

The development of synthetic routes for the formation of robust porous organic polymers (POPs) with well‐defined nanoscale morphology is fundamentally significant for their practical applications. The thermodynamic characteristics that arise from reversible covalent bonding impart intrinsic chemical instability in the polymers, thereby impeding their overall potential. Herein, a unique strategy is reported to overcome the stability issue by designing robust imidazole‐linked POPs via tandem reversible/irreversible bond formation. Incorporating inherent rigidity into the secondary building units leads to robust microporous polymeric nanostructures with hollow‐spherical morphologies. An in‐depth analysis by extensive solid‐state NMR (1D and 2D) study on 1H, 13C, and 14N nuclei elucidates the bonding and reveals the high purity of the newly designed imidazole‐based POPs. The nitrogen‐rich polymeric nanostructures are further used as metal‐free electrocatalysts for water splitting. In particular, the rigid POPs show excellent catalytic activity toward the oxygen evolution reaction (OER) with long‐term durability. Among them, the most efficient OER electrocatalyst (TAT‐TFBE) requires 314 mV of overpotential to drive 10 mA cm−2 current density, demonstrating its superiority over state‐of‐the‐art catalysts (RuO2 and IrO2).

Accelerated Oxygen Evolution Kinetics by Engineering Heterojunction Coupling of Amorphous NiFe Hydr(oxy)oxide Nanosheet Arrays on Self‐Supporting Ni‐MOFs

“…There is no apparent attenuation in continuous operation and the response time from one to another step is less than 0.1 s (Figure 4e), illustrating excellent mass transportation, conductivity, and mechanical robustness of the A-NiFe HNSAs/SNMs-NF toward OER catalysis. [28] It is noted that A-NiFe HNSAs/SNMs-NF-9 h is the most prominent, which only requires small overpotentials (Figure 4f). Meanwhile, we have investigated the effect of the content of Fe in the catalyst on catalytic activity and stability.…”

Redox insights and OER activity in 3D-MOFs: the role of alkali metal ions

“…Electrocatalytic oxygen evolution reaction (OER) has become the most prominent and promising tool for the water-splitting reaction to produce hydrogen electrochemically. 1,2 Since the splitting of water is associated with the celebrated bottleneck of the four-electron-four proton-transfer process, a suitable electrocatalyst to minimize the kinetic barrier with lower energy input is essential for conducting the process. 3,4 In this context, the search for suitable electrocatalysts that are cheap, efficient and environmentally friendly has become the most impactful area of hydrogen evolution research towards alternative green energy.…”

Catalytic Linkage Engineering of Covalent Organic Frameworks for the Oxygen Reduction Reaction

“…The linkages determined the properties of COFs, such as chemical stability and electron/charge transfer ability in addition to the building blocks. [12] However, the important roles of linkages toward catalyzing ORR are ignored, and which linkage is more suitable for ORR is still under investigation.…”