Reverse doping strategy for efficient acid oxygen evolution

On July 5, 2023, the team of Xing Wei researchers from the Changchun Institute of Applied Chemistry, Chinese Academy of Sciences published an article titled “Inverse doping IrOx/Ti with weakened Ir-O interaction toward stable and efficient acidic oxygen evolution” in the journal Chem.

In this study, a reverse-doped IrOx/Ti model catalyst is reported, through which only a small amount of Ti doping can form a large number of Ir-O-Ti local structures, which greatly promotes the activity and stability of OER. This work provides a new idea for constructing atomic-level interfaces and improving site activity and stability.

The corresponding authors of the paper are Xing Wei, Ge Junjie, Wang Ying; The first author is Wang Yibo.

Proton exchange membrane water electrolysis (PEMWE) technology coupled with renewable energy technology provides an ideal solution for the cheap production of green hydrogen. Slow acid oxygen evolution (OER) is one of the main obstacles hindering the commercialization of PEMWE. At present, only iridium-based catalysts can have suitable activity and stability, but the high cost and low natural abundance of Ir require the development of highly active, more cost-effective and durable electrocatalysts to improve the intrinsic catalytic activity and utilization of Ir. The introduction of a second metal into IrOx not only reduces the use of the precious metal Ir, but also effectively increases its activity. Among them, the Ir-Ti system has been extensively studied. However, the effect of the interface between IrOx and TiO2 (Ir-O-Ti) on OER is still unclear at the atomic scale. In addition, it was found that when the Ti doping amount was less than 20%, the Ir-Ti composite oxide could maintain good conductivity, which inspired the research group to build a reverse doped IrOx/Ti catalyst.

In this work, based on the catalyst design idea of reverse doping, Xing’s team incorporated IrOx/Ir surface through atomic-scale Ti to form an Ir-O-Ti local structure on its 2 nm surface. Ti doping of only 1.92 wt% increases Ir site activity by a factor of 3.6 and the stability number by an order of magnitude. This excellent stability is attributed to a large number of Ir-O-Ti local structures. A variety of characterizations and DFT calculations show that in this local structure, the Ti site generates electrons to the adjacent Ir site through the bridge O, which weakens the Ir-O interaction and promotes the adsorption and precipitation mechanism of the Ir site, thereby enhancing the activity. At the same time, Ti reduces the dissolution of Ir by inhibiting the excessive oxidation of Ir species and the occurrence of lattice oxygen mechanism (LOM), so the catalyst has excellent stability.

Figure 1: Morphology and structural characterization.


Figure 2: OER performance.

Figure 3: Mechanism of Ir-O-Ti promotion.

Figure 4: DFT calculation.

The results show that this work provides a new idea for the construction of atomic-level interfaces and the enhancement of site activity and stability. (Source: Science Network)

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