In situ observation of reactive oxygen species forming on oxygen-evolving iridium surfaces

Abstract

In situ XAS measurements reveal that electron-deficient oxygen species form during OER on IrOx and correlate with catalytic activity.

A Dissolution/Precipitation Equilibrium on the Surface of Iridium‐Based Perovskites Controls Their Activity as Oxygen Evolution Reaction Catalysts in Acidic Media

“…

Recently,I r V -based perovskite-like materials were proposed as oxygen evolution reaction (OER) catalysts in acidic media with promising performance.H owever,i ridium dissolution and surface reconstruction were observed, questioning the real active sites on the surface of these catalysts.In this work, Sr 2 MIr (V) O 6 (M = Fe,Co) and Sr 2 Fe 0.5 Ir 0.5 (V) O 4 were explored as OER catalysts in acidic media. [7][8][9][10][11] Thef ew materials established as suitable OER catalysts in acidic media are mostly Ir-based metal oxides,such as rutile IrO 2 , [12,13] 14] or more recently Ni-substituted IrO x . 4H + + O 2 + 4e À ).

…”

“…[1,2] While alarge variety of transition metal oxides have been studied as promising OER catalysts in alkaline media, [3][4][5][6] thedesign of active and stable catalysts in acidic media has proven challenging. [11,20,21] However,dissolution of iridium, alkali and/or rare earth elements in acidic electrolytes has been observed after close examinations of some Ir V -based perovskites,such as La 2 LiIr (V) O 6[20] and Ba 2 PrIr (V) O 6 , [7,19] indicating their drastic structural instabilities in harsh acidic conditions. [15][16][17] Recently,Ir-based perovskites have been reported as promising candidates in acidic media.…”

“…[7][8][9][10][11] Thef ew materials established as suitable OER catalysts in acidic media are mostly Ir-based metal oxides,such as rutile IrO 2 , [12,13] electrodeposited IrO x [14] or more recently Ni-substituted IrO x . [11,20,21] However,dissolution of iridium, alkali and/or rare earth elements in acidic electrolytes has been observed after close examinations of some Ir V -based perovskites,such as La 2 LiIr (V) O 6 [20] and Ba 2 PrIr (V) O 6 , [7,19] indicating their drastic structural instabilities in harsh acidic conditions. [18][19][20] Thehigh OER activity of these Ir-based perovskites was ascribed to the formation of electrophilic O (IÀ) surface species favoring the nucleophilic attack of water.…”

“…[1,2] While alarge variety of transition metal oxides have been studied as promising OER catalysts in alkaline media, [3][4][5][6] thedesign of active and stable catalysts in acidic media has proven challenging. [7][8][9][10][11] Thef ew materials established as suitable OER catalysts in acidic media are mostly Ir-based metal oxides,such as rutile IrO 2 , [12,13] electrodeposited IrO x [14] or more recently Ni-substituted IrO x . [15][16][17] Recently,Ir-based perovskites have been reported as promising candidates in acidic media.…”

Honeycomb‐Like Nitrogen‐Doped Carbon 3D Nanoweb@Li2S Cathode Material for Use in Lithium Sulfur Batteries

“…[17,18] The N1ss pectrum of the HCNs was divided into three peaks at 402.7, 400.9, and 398.2 eV,w hich can be attributed to graphitic, pyrrolic, and pyridinic Ns pecies, respectively. [20] Figure 5a,b shows the galvanostatic charge-discharge profiles of the Li 2 S@HCNs and Li 2 S@AB electrodes at ac onstant current rate of C/10 in av oltage range from 1.7 to 2.7 V. For the discharger eactions, two discharge plateaus appeared at 2.3 and 2.1 V, which are ascribed to the two-step reduction reactions of elemental sulfur to long-chain lithium polysulfides (Li 2 S n ,4 < n < 8, 2.3 V) and the subsequent reaction of the long-chain lithium polysulfides to form either Li 2 S 2 or Li 2 Ss pecies (2.1 V), respectively. [20] Figure 5a,b shows the galvanostatic charge-discharge profiles of the Li 2 S@HCNs and Li 2 S@AB electrodes at ac onstant current rate of C/10 in av oltage range from 1.7 to 2.7 V. For the discharger eactions, two discharge plateaus appeared at 2.3 and 2.1 V, which are ascribed to the two-step reduction reactions of elemental sulfur to long-chain lithium polysulfides (Li 2 S n ,4 < n < 8, 2.3 V) and the subsequent reaction of the long-chain lithium polysulfides to form either Li 2 S 2 or Li 2 Ss pecies (2.1 V), respectively.…”