Electrocatalytically Active Silver Organic Framework: Ag(I)‐Complex Incorporated in Activated Carbon

Abstract

Silver is known as a viable alternative for platinum group metals for the catalysis of the oxygen reduction reaction in alkaline electrolyte. Unlike most other platinum-group metal-free catalysts, usually organo-metallic complexes, silver is commonly used in its metallic form (Ag(0)). Herein, we describe the preparation, characterization, and electrochemical activity of a unique silver-based catalyst, based on Ag(I) ions coordinated to oxygen groups in an organic ligand (benzene tricarboxylic acid -BTC) which forms a metal organic framework, similar to first-row transition metal-based catalysts in metal organic frameworks. When the silver-based catalyst is incorporated in a porous carbon support, it exhibits high electrocatalytic activity for the oxygen reduction reaction, with a distinct electrochemical behavior, different than metallic silver. In addition, the use of the ionic form of the silver, which is atomically dispersed, allows to lower its loading of the metal by at least one order of magnitude when compared to other reported silver-based oxygen reduction reaction catalysts. Results and DiscussionAg-BTC and Ag-BTC@AC were synthesized according to the procedure described in the experimental section. Two-probes bulk conductivity measurements showed that the AgBTC is practically an insulator, as many other metal-BTC, [5,8] unlike the high electronic conductivity of metallic silver. Therefore, AgBTC cannot be utilized as a stand-alone electrocatalyst/electrode in [a] S.

Conductive Ytterbium Metal–Organic Framework Composite: A Lanthanide-Based Complex ORR Catalyst

“…As can be seen in the RDE results in Figure , the YbMOF-carbon composites have much higher electrocatalytic activity than the ligand and the AC without metal (BTC@AC). The carbon presents only a partial reduction of the oxygen to peroxide anion, instead of hydroxide, via the less desired two-electron reduction mechanism. ,, On the other hand, the YbBTC@AC (and YbBTC@BP2000 as well in Figure S5) demonstrates relatively high performance for a PGM-free ORR electrocatalyst, especially for a catalyst that did not undergo any thermal treatment, a process that has been proven in many cases to increase the electrocatalytic activity, with the onset and half-wave potentials of 0.88 and 0.75 V vs RHE, respectively. It can be speculated from the two different waves in the RDE voltammogram that the composite reduces oxygen via the 2 + 2 electrons mechanism, with the majority of the oxygen reduced to peroxide anion at the lower overpotential potential region, followed by the reduction to hydroxide at the higher overpotential (second wave).…”

“…Electrical Conductivity Measurements. Bulk conductivity of the electrocatalyst powder was measured using a twoprobe measurement method reported by Elbaz et al 18,35,36 Thirty milligrams of powder was placed in a 0.25″ diameter Teflon cylinder and compacted by two 0.25″ diameter alumina rods with tips covered in Au. The rods were two-bore in configuration, permitting Au wire to contact the Au foil.…”

“…16 In our previous studies, we showed that oxygen in the form of carboxylic acid (benzene tricarboxylic acid, BTC) can replace nitrogen as the ligand, and other first-row transition metals such as Mn or even second-row transition-metal complexes can lead to high catalytic activity. 17,18 Another class of metal centers that has been investigated in recent years is the f-block lanthanides, which have shown interesting properties that render them suitable for various applications. 19−25 Among them are ytterbium coordination complexes 26 and MOFs based on oxygen ligands.…”

Two binuclear silver(I) complexes containing V‐shaped bis (benzimidazole) ligands: Syntheses, structures, and electrochemical sensing toward hydrogen peroxide

“…[ 31 ] Gonen et al have reported a benzene tricarboxylic acid Ag(I) complex and studied its electrocatalytic activity toward oxygen reduction reaction (ORR). [ 32 ] Sherine et al have synthesized a 2‐Mercaptobenzothiazole (MBT) Ag(I) complex and the mechanism for its induction of apoptosis was confirmed by electrochemical analysis. [ 33 ]…”

“…[31] Gonen et al have reported a benzene tricarboxylic acid Ag(I) complex and studied its electrocatalytic activity toward oxygen reduction reaction (ORR). [32] Sherine et al have synthesized a 2-Mercaptobenzothiazole (MBT) Ag(I) complex and the mechanism for its induction of apoptosis was confirmed by electrochemical analysis. [33] In this work, we selected two different V-shaped bis (benzimidazole) ligands, 1,3-bis[(N-methyl-benzimidazole)methylene]-2-aniline (L 1 ) and 1,3-bis[(Nethyl-benzimidazole)methylene]-2-aniline (L 2 ), with isophthalic acid as auxiliary ligand, two new Ag(I) complexes, [Ag 2 L 1 2 (isophthalate)]Á(C 2 H 5 OH) 5 (1) and [Ag 2 L 2 2 (isophthalate)] (2), were synthesized and characterized by elemental analysis, IR and UV-vis spectra, and single crystal X-ray diffraction.…”