Mechanical Interlocking Enhances the Electrocatalytic Oxygen Reduction Activity and Selectivity of Molecular Copper Complexes

Abstract

Efficient O2 reduction reaction (ORR) for selective H2O generation enables advanced fuel cell technology. Nonprecious metal catalysts are viable and attractive alternatives to state-of-the-art Pt-based materials that are expensive. Cu complexes inspired by Cu-containing O2 reduction enzymes in nature are yet to reach their desired ORR catalytic performance. Here, the concept of mechanical interlocking is introduced to the ligand architecture to enforce dynamic spatial restriction on the Cu coordination site. Interlocked catenane ligands could govern O2 binding mode, promote electron transfer, and facilitate product elimination. Our results show that ligand interlocking as a catenane steers the ORR selectivity to H2O as the major product via the 4e– pathway, rivaling the selectivity of Pt, and boosts the onset potential by 130 mV, the mass activity by 1.8 times, and the turnover frequency by 1.5 fold as compared to the noninterlocked counterpart. Our Cu catenane complex represents one of the first examples to take advantage of mechanical interlocking to afford electrocatalysts with enhanced activity and selectivity. The mechanistic insights gained through this integrated experimental and theoretical study are envisioned to be valuable not just to the area of ORR energy catalysis but also with broad implications on interlocked metal complexes that are of critical importance to the general fields in redox reactions involving proton-coupled electron transfer steps.

High‐Valence Oxides for High Performance Oxygen Evolution Electrocatalysis

“…Unfortunately, most of HVOs are unstable or inactive at the cathodic potential for ORR/HER (U < 1.23 V vs RHE for ORR and U < 0 V vs RHE for HER), although some bifunctional activities of HVOs are recently reported, such as Ir/Ni(OH) 2 (HER/OER: Ir 5+ ) [123] and Mg-doped LaNiO 3 nanofibers (ORR/OER: Ni 3+/4+ ). [124] Specific structures with multi-phases, such as core-shell structures and coordinated hybrids or complexes, [125,126] may be developed to stabilize the high-valence metal sites at the cathodic potential.…”

Template Assisted One‐Pot Synthesis of [2], Linear [3], and Radial [4]Catenane via Click Reaction

“…[6] Among MIMs, catenanes are a class of interlocked molecules and are fascinating due to their molecular topologies. In recent times, many applications, such as in catalysis, [7] photo-catalysis, [8] as electro catalyst, [9] a catalyst for click reaction, [10] memory device, [11] and guest molecule encapsulation, [12] etc. have surfaced for this class of molecules.…”

An Ultrasmall Ordered High-Entropy Intermetallic with Multiple Active Sites for the Oxygen Reduction Reaction

“…Proton exchange membrane fuel cells (PEMFCs) are considered to be promising sustainable energy systems which can efficiently convert the chemical energy of hydrogen into electrical energy . Nevertheless, the oxygen reduction reaction (ORR), involving multiple electron and proton transfers at the cathode, limits the application of PEMFCs owing to the sluggish kinetics. − Currently, Pt-based catalysts are still the most essential catalysts for the ORR, demonstrating excellent activity and durability in acidic electrolytes. , Due to the scarcity of platinum resources and the high cost, the activity of Pt-based catalysts should be urgently improved to reduce the platinum loading in catalysts . Previous studies have revealed that alloying Pt with other transition metals (TMs) is one of the most effective methods for optimizing the surface electronic structure to promote the electrocatalytic performance of Pt-TM catalysts. − Despite the considerably improved ORR activities, Pt-TMs alloys are commonly prepared as face-centered cubic (fcc)-type solid solution structures, which limits the stability of the TMs under the acidic ORR conditions, thus compromising the advantages of the TMs in Pt-TM alloys. , …”