Ni–Co Codoping Breaks the Limitation of Single-Metal-Doped IrO₂with Higher Oxygen Evolution Reaction Performance and Less Iridium

Abstract

Synthesizing solid solutions of IrO 2 via doping is known to be a viable approach for effectively using iridium metal by enhancing its intrinsic properties. However, such composites at certain fractional values of dopants realize the substitution limit because of lattice mismatch. Here, on the basis of density functional theory studies and experimentation, we demonstrate codoping as an effective approach to overcome this result with an outstanding oxygen evolution reaction (OER) activity. Nickel and cobalt as the case dopants for the host structure IrO 2 atomically substituted 50% of the precious metal. As a new structural insight, the decreased crystal energy was determined to be the key factor for considerable insertion of dopants. Furthermore, the synthesized codoped IrO 2 reflected an overpotential of only 285 mV at a current density of 10 mA•cm −2 , which is appreciably lower than the 320 and 330 mV for individually doping cobalt and nickel, respectively. Our presented approach suggests further OER optimization methods with extensive reduction of precious metals.

Ultrasmall Ru/Cu‐doped RuO2 Complex Embedded in Amorphous Carbon Skeleton as Highly Active Bifunctional Electrocatalysts for Overall Water Splitting

“…It is well known that doping heteroatom is another effective method to regulate the electronic structure of active sites . Yang and co‐workers have demonstrated NiCo codoping as an effective approach to enhance intrinsic property for OER of IrO 2 . The study of Krtil and co‐workers indicated that Zn cations substitution into the crystal lattice of RuO 2 leads to the formation of a metastable material, which hinders the formation of surface confined peroxo species and plays an essential role in both oxygen and chlorine evolution reactions .…”

Porosity‐Engineering of MXene as a Support Material for a Highly Efficient Electrocatalyst toward Overall Water Splitting

“…Co is promising candidate among 3d transition metals in terms of its OER electrocatalytic reactivity because its d‐orbital state can offer variable electronic and possibly structural modification to enhance the surface electrocatalysis . Moreover, the coexistence of Co and Ir has been demonstrated to improve the OER activity significantly because of the increased orbital overlap with O 2p and the fluctuation in the electronic density of the IrCo alloy facilitates surface electrode interaction with intermediate adsorbates to result in an optimised surface–oxygen interaction energy. In addition, the role of support materials can affect the whole electrocatalyst system significantly .…”

“…However, these catalysts have still not reached the necessary performance. Among fascinating efforts in this area, the rational design of bimetallic compounds of precious metals with earth‐abundant 3d transition metals (e.g., Ni, Co, Fe) was rationalised as wise approach because of the modification of the d‐band electron configuration and absorption energy . Recently, IrM (M=Co, Ni, CoNi) multi‐metallic hollow nanocrystals, synthesised by etching Ir‐based solid nanocrystals were shown to have an excellent activity for the OER and overall water splitting in acid media because of the reduction of the adsorption energy of oxygen intermediates and the favourable hollow feature of the alloy of Ir with 3d transition metals .…”

“…Amongf ascinating efforts in this area, the rational design of bimetallic compounds of preciousm etals with earthabundant 3d transitionmetals (e.g.,N i, Co, Fe) was rationalised as wise approach because of the modification of the d-band electronc onfigurationa nd absorption energy. [55][56][57][58][59][60][61][62] Recently, IrM (M = Co, Ni, CoNi)m ulti-metallic hollow nanocrystals, synthesised by etching Ir-baseds olid nanocrystals were shown to have an excellent activity for the OER and overall water splitting in acid media because of the reductiono ft he adsorption energy of oxygen intermediates and the favourable hollow feature of the alloy of Ir with 3d transition metals. [63] However,t he bare hollow nanocrystals may collapse during the synthesis or electrocatalysis, whichc an lead to the degradation of the reactivity and stability of the electrocatalysts.…”

Effective Strain Engineering of IrO2 Toward Improved Oxygen Evolution Catalysis through a Catalyst‐Support System

“…(b) Tafel curves for IrO 2 and Ir−Co‐Mn materials. (c) Comparisons of Tafel slopes; Ir mass activity and the overpotential at 10 mA cm −2 for different catalysts (C1 is the Ir0.4/Mn0.6 composite, C2 is IrO 2 /Mn−Co(2 : 1)‐Bir in this work, C3 is INC‐50, C4 is IrNi 0.57 Fe 0.82 , C5 is IrO x /ATO, C6 is Ir 0.54 Co 0.46 O y , and C7 is IrO 2 ‐150). (d) Chronopotentiometric measurements at 100 mA cm −2 .…”