Iridium‐Chromium Oxide Nanowires as Highly Performed OER Catalysts in Acidic Media

Abstract

The oxygen evolution reaction (OER) severely restricts the efficiency of electrolyzers due to its sluggish kinetics. In particular, only a few OER electrocatalysts, such as expensive and scarce iridium (Ir)-based materials, have been developed to function in acidic media. Therefore, the exploration of efficient and stable electrocatalysts with decreased precious metal content for the OER in acid is desired. Herein, chromium (Cr)incorporated IrO x solid solution nanowires not only exhibit high catalytic activity with a low overpotential of 250 mV at 10 mA cm À 2 , but also display robust catalytic performance without a decay in activity throughout 25 h of testing at 10 mA cm À 2 in 0.5 M H 2 SO 4 . This improved catalytic performance for the Cr-incorporated IrO x electrocatalysts is ascribed to an abundance of exposed active sites, tuned electronic states, optimized binding energy for intermediates on the catalyst surface and the consequent facile reaction kinetics.

Tuning the intrinsic catalytic activities of oxygen-evolution catalysts by doping: a comprehensive review

“…Qu et al synthesized Cr-doped IrO x nanowires and evaluated their OER activity in 0.5 M H 2 SO 4 electrolyte. 43 The catalyst exhibits excellent OER activity with 25 h durability without any decay in activity. This high activity was ascribed to an increase in active site number and facile adsorption of OER intermediates via electronic structure tuning.…”

“…Researchers doped RuO 2 with a small amount of Ir (Ru x Ir 1-x O 2 ) and observed significant improvement in stability without sacrificing OER performance. 37 Another way of enhancing the OER activity with lower total noble metal content is doping with earth-abundant metals, such as Cu, 38,39 Ni, 40 Co, 40,41 Mn, 42 Cr, 43,44 Ce, 45 W, 46 Mg, 47 and Zn. 48 For example, Cu-doped IrO 2 (Cu 0.3 Ir 0.7 O δ ) displays improved OER activity in acid, neutral and basic media, compared to pristine IrO 2 .…”

Recent Development of Oxygen Evolution Electrocatalysts in Acidic Environment

“…[72][73][74] The studies on morphology are classified into three categories in this section. First, 1D structures, such as nanoneedles [72] and nanowires [75][76][77][78] showing high conductivity have been prepared for improving OER activity. For example, ultrathin IrO 2 nanoneedles were introduced as electrocatalyst for OER in acidic electrolyte (Figure 5a,b).…”

“…As for Ir‐Ru oxides, although the homogeneous solid solution phase is the most general form due to the similar atomic radius of Ir 4+ and Ru 4+ , the separate IrO 2 and RuO 2 phases may also be present. [ 178 ] Similarly, some mixed oxides, such as Cr‐Ru oxides (Cr 0.6 Ru 0.4 O 2 ), [ 101 ] W 0.09 Ir 0.01 O 3− σ (1 wt%), [ 100 ] and Cr‐incorporated IrO x , [ 77 ] possess solid solution phases whereas some others, such as pyrolyzed‐leached Ir 0.7 Co 0.3 O x , [ 103 ] have separate phases. By introducing the same elements, the OER activity of catalysts may not be consistent, because of the various synthesis conditions and surface structures.…”

Recent Progress in Advanced Electrocatalyst Design for Acidic Oxygen Evolution Reaction

“…Ir 0.6 Cr 0.4 O x nanowires annealed at 350 °C require an overpotential of 250 mV for 10 mA cm −2 in 0.5 m H 2 SO 4 and show durable stability of 25 h at 10 mA cm −2 . [105] In addition to the metal element doping, nonmetal element doping can also improve the activity and stability of IrO 2 , for example, F doping. [167,168] Furthermore, ternary oxides catalysts were also developed such as ternary IrO 2 -RuO 2 -based and ternary IrO 2 -SnO 2 -based oxides.…”