Atomic Iridium Incorporated in Cobalt Hydroxide for Efficient Oxygen Evolution Catalysis in Neutral Electrolyte

Abstract

Developing highly efficient catalysts for oxygen evolution reaction (OER) in neutral media is extremely crucial for microbial electrolysis cells and electrochemical CO reduction. Herein, a facile one-step approach is developed to synthesize a new type of well-dispersed iridium (Ir) incorporated cobalt-based hydroxide nanosheets (nominated as CoIr) for OER. The Ir species as clusters and single atoms are incorporated into the defect-rich hydroxide nanosheets through the formation of rich Co-Ir species, as revealed by systematic synchrotron radiation based X-ray spectroscopic characterizations combining with high-angle annular dark-field scanning transmission electron microscopy measurement. The optimized CoIr with 9.7 wt% Ir content displays highly efficient OER catalytic performance with an overpotential of 373 mV to achieve the current density of 10 mA cm in 1.0 m phosphate buffer solution, significantly outperforming the commercial IrO catalysts. Further characterizations toward the catalyst after undergoing OER process indicate that unique Co oxyhydroxide and high valence Ir species with low-coordination structure are formed due to the high oxidation potentials, which authentically contributes to superior OER performance. This work not only provides a state-of-the-art OER catalyst in neutral media but also unravels the root of the excellent performance based on efficient structural identifications.

Densely Populated Single Atom Catalysts

“…The 400‐SWNT/Pt exhibited a low overpotential of 27 mV to achieve current densities of 10 mA cm −2 , which are similar to those of Pt/C. Other precious metal‐based catalysts have also been reported, Zhang et al developed a well‐dispersed atomic Ir incorporated Co‐based hydroxide nanosheets with 9.7 wt% Ir. This catalyst displayed highly efficient OER catalytic performance with overpotential 373 mV at the current density of 10 mA cm −2 in a neutral electrolyte.…”

Fabrication of Superior Single‐Atom Catalysts toward Diverse Electrochemical Reactions

“…To date, the IrO 2 and RuO 2 noble metal oxides are regarded as active catalysts for this reaction . Song and co‐workers synthesized single Ir atoms and Ir clusters on 2D Co(OH) 2 for enhancement of its OER activity . These atomic Ir species anchored on defect‐rich Co(OH) 2 nanosheets showed excellent OER performance with rapid catalytic kinetics.…”

Mono‐/Multinuclear Water Oxidation Catalysts

“…[41] In addition, Das [43] Additionally,abinuclear Mn-based catalyst, [(terpy)(SO 4 )Mn IV (O) 2 Mn IV (O 4 S)(terpy)] (terpy:2 ,2':6',2''-terpyridine) can also be synthesized by using MnSO 4 and terpy as the precursors and potassium peroxomonosulfate as the oxidant. Some highly dispersed metal-supported WOCs can be synthesized through chemical reduction.…”

“…[99] Kinetic studies showedt hat oxygen evolutionw as rapid if cerium(IV) ammonium nitratew as used as the oxidant, and DFT calculations demonstrated that the attack of water on M=Os pecies was ak ey step in OÀOb ond formation.B rudvig and co-workers used an electrochemical quartz crystal nanobalance (EQCN) to revealt he homo-o rh eterogeneousn ature of WOCs. [138] In 2018, an ew type of iridium-based catalyst, iridium-incorporated cobalt hydroxide (Ir-Co),w as synthesized by Zhang et al [41] In 1.0 m phosphate-buffered saline (PBS), Ir-Co-0.2 (the molar ratio of Ir/ Co was 0.2) showedalow potential( 373 mV at j = 10 mA cm À2 ). [137] Iridium-substitutedP OMs can also catalyze the water oxidation with as trong oxidant, such as [Ru(bipy) 3 ] 3 + .…”