Electrochemical transformation of Prussian blue analogues into ultrathin layered double hydroxide nanosheets for water splitting

Abstract

Herein, we demonstrate a template directed route for the synthesis of self-supported cobalt-iron based Prussian blue analogues (PBAs). The PBAs are electrochemically transformed into layered double hydroxides to produce excellent...

Realizing electrochemical transformation of a metal–organic framework precatalyst into a metal hydroxide–oxy(hydroxide) active catalyst during alkaline water oxidation

“…2,6,[20][21][22][23][24][25][26][27][28][29][30][31][32][33] In this respect, transition metal-based MOF-derived hydroxides, oxides, phosphides, chalcogenides, etc., have been demonstrated with promising electrochemical water oxidation activity. [34][35][36][37][38][39][40][41][42][43][44][45] Comprising a large electrochemical surface area, exposed facets, an increased number of active sites, and tunable electronic properties, MOFderived catalysts have attained special attention for electrochemical processes. For example, NiCo-PBA derived Ni x Co 3Àx O 4 demonstrated 10 mA cm À2 current density for the OER at only 287 mV overpotential.…”

“…[67][68][69][70][71][72][73][74] In these cases, the MOF plays the role of a precatalyst and undergoes a series of structural reconstruction and selfassembly processes during the OER to form ultrathin M(OH) 2 -M(O) x (OH) y nanosheets. 36,56,58,[61][62][63]69,[75][76][77][78] MOFs have several advantages as a precatalyst like (i) the synthesis of MOFs is easy, facile, and scalable, (ii) the structural and electronic properties of MOFs can be easily tuned, (iii) MOFs undergo bulk and complete electrochemical transformation to form ultrathin M(OH) 2 -M(O) x (OH) y nanosheets and (iv) the required time for the electrochemical transformation is surprisingly low (few seconds to minutes). 7,9,12,79,80 Another advantage of using MOFs as the precatalyst comes from the formation of a self-supported catalyst system, which provides enhanced electronic conductivity, improved charge transport, and strong catalyst-support interaction.…”

“…7,9,12,79,80 Another advantage of using MOFs as the precatalyst comes from the formation of a self-supported catalyst system, which provides enhanced electronic conductivity, improved charge transport, and strong catalyst-support interaction. 36,63,67,73,81 As a result, the stability of MOF-derived catalysts is exceptionally high and can produce oxygen for days with a minimum loss of the initial current density.…”

“…The structural reconstruction of MOFs under oxidizing anodic potential includes a series of changes like phase transformation, structural reorganization, morphological changes, and compositional tuning. 7,36,[82][83][84][85] In alkaline medium, MOFs are observed to undergo hydrolysis and oxidation under the applied anodic potential to form M(OH) 2 -M(O) x (OH) y nanosheets. The alkaline electrolyte, having OH À ions, promotes the hydrolysis of the metal-ligand coordination sites and destroys the framework irreversibly to form hydroxide and hydrated metal ion species.…”

“…62 The electrochemically synthesized M(OH) 2 -M(O) x (OH) y nanosheets show atomic-level thickness, a large electrochemical surface area, a tuned electronic structure, and a large number of accessible active sites. 36,56,58,[61][62][63]69,[75][76][77][78] In addition, a self-supported catalyst system with improved charge transport, high mechanical stability, and strong catalyst-support interaction has been achieved by the electrochemical transformation approach. Hence, the activity and the stability of the catalyst are dramatically improved for water oxidation.…”