Surface Immobilization of Molecular Electrocatalysts for Energy Conversion

Abstract

Electrocatalysts are critically important for a secure energy future, as they facilitate the conversion between electrical and chemical energy. Molecular catalysts offer precise control of structure that enables understanding of structure-reactivity relationships, which can be difficult to achieve with heterogeneous catalysts. Molecular electrocatalysts can be immobilized on surfaces by covalent bonds or through non-covalent interactions. Advantages of surface immobilization include the need for less catalyst, avoidance of bimolecular decomposition pathways, and easier determination of catalyst lifetime. This Minireview highlights surface immobilization of molecular electrocatalysts for reduction of O , oxidation of H O, production of H , and reduction of CO .

Immobilization of Molecular Catalysts for Enhanced Redox Catalysis

“…The immobilization of homogeneous catalysts on various insoluble supports such as a siliceous material makes the immobilized catalyst insoluble in the reaction solution, providing great advantages for the easy separation of the catalyst from the reaction mixture, the fast isolation of the reaction products, and catalyst recovery and recycling by simple filtration . The immobilization of homogeneous catalysts also allows insoluble catalysts, which would otherwise be aggregated, to be well dispersed in the reaction medium such as water, resulting in the significant enhancement in the catalytic activity.…”

“…In general, the supported catalyst may be more sterically hindered and hence less accessible to substrates as compared to its non‐supported counterpart, while the selectivity may be enhanced by the steric effect. Catalyst instability in the homogeneous phase is mainly caused by bimolecular deactivation pathways, which are prevented by immobilization of the catalyst to isolate the catalyst reactive sites …”

“…The immobilization of homogeneous catalysts on various insoluble supports such as as iliceous material makes the immobilized catalysti nsoluble in the reactions olution,p roviding great advantages for the easy separation of the catalystf rom the reaction mixture, the fast isolation of the reaction products, and catalyst recovery and recycling by simple filtration. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] The immobilization of homogeneous catalysts also allows insoluble catalysts, which would otherwise be aggregated, to be well dispersed in the reaction medium such as water, resultingi nt he significant enhancement in the catalytic activity.T he use of water as solvent with immobilizedc atalysts also call attentiont ot he importance of the requirements of green chemistry. [21][22][23][24][25][26] In general,t he supported catalyst may be more sterically hindered and hence less accessible to substrates as compared to its non-supported counterpart,w hile the selectivity may be enhanced by the steric effect.…”

A Functional Hydrogenase Mimic Chemisorbed onto Fluorine‐Doped Tin Oxide Electrodes: A Strategy towards Water Splitting Devices

“…Strategies to afford robust immobilization on conductive electrode surfaces, which are key for the development of devices, are relatively limited. The potential and advantages of immobilizing molecular catalysts have already been illustrated for cobalt‐ and nickel‐based catalysts, which have been anchored onto various materials through their organic ligand structure . Heterogenization of molecular diiron hydrogenase models onto supporting matrices, including metal–organic frameworks, molecular sieves, hydrogels, or polymers, has been shown to be beneficial for the activity and stability of the catalytic centers.…”

“…The potential and advantages of immobilizing molecular catalysts have already been illustrated for cobalt- [30][31][32][33][34][35][36][37][38][39][40] and nickel-based catalysts, [41][42][43][44] whichh ave been anchored onto variousm aterials through their organic ligand structure. [45] Heterogenization of molecular diiron hydrogenasem odels onto supporting matrices, including metal-organic frameworks, [46] molecular sieves, [47] hydrogels, [48] or polymers, [49] has been shown to be beneficial for the activity and stabilityo ft he catalytic centers.…”