# Electrocatalysis for the Oxygen Evolution Reaction in Acidic Media: Progress and Challenges
## 3 Tailoring Strategies for Effective OER Electrocatalysts
### Metal-Support Interaction  
The interface between the metal center and the support will cause the re-arrangement of electrons originating from the support and anchored atoms [69, 73]. The re-arranged electrons that have a significant impact on the catalytic performance will be confined in a space several atomic layers thick at the interface [74]. The magnitude and direction of the charge transfer are driven by differences in the Fermi level of the catalytic center and the support [50]. In addition, due to the special microenvironment at the interface, the interface sites will be in direct contact with the catalytic center, the carrier, and the reactants in order to promote the occurrence of synchronous reactions [37]. Additionally, the interface is conducive to the accumulation of excess charge during the charge transfer process, which will strongly promote the catalytic reactions at the interface [75].  
SnO\({}_{2}\) and TiO\({}_{2}\)-based compounds are commonly used as supports due to their characteristic of stability [76, 77]. In order to improve their low charge-transfer rate, extensive studies have modified them to improve the conductivity. For SnO\({}_{2}\), Sb doping is often used to prepare Sb-SnO\({}_{2}\) (ATO), and the conductivity of the material will be improved due to the increased electron carrier density caused by donor doping [78]. Moreover, the specific surface area and pore volume of SnO\({}_{2}\) can be improved by destroying the long-range order of the original atomic arrangement so as to provide more anchor sites for IrO\({}_{2}\) nanoparticles [77]. The interaction between IrO\({}_{2}\) and the support, the cross-linking morphology of IrO\({}_{2}\), and the porous structure can improve the OER performance of the catalyst. [PERSON]'s group designed a kind of Sb-SnO\({}_{2}\) nanowire carrier by an electrospinning method (Figure 3a) [37]. The conductivity can reach 0.83 S-cm\({}^{-1}\). Compared with pure IrO\({}_{2}\), the catalytic activity of supported IrO\({}_{2}\)/Sb-SnO\({}_{2}\) exhibits significantly improved mass activity, benefiting from the porous structure and the high electronic conductivity of the Sb-SnO\({}_{2}\) support [37].  
In addition to metal oxides, metal carbides have also emerged as promising OER carriers because of their high conductivity and stability. A TaC-supported IrO\({}_{2}\) catalyst sprayed by [PERSON] et al. showed the lowest charge transfer resistance and the highest current density when the loading of IrO\({}_{2}\) reached 70 wt%, which was significantly improved compared with unsupported IrO\({}_{2}\) (Figure 3b) [79]. When TiC is employed as the support for Ir in PEMWE, Ir nanoparticles can be evenly distributed on the TiC surface, and the pore volume of Ir/TiC is twice that of pure Ir. All these advantages make the OER catalytic performance of Ir/TiC much better than that of pure Ir [80].  
In general, the existence of a support has two major advantages. On one hand, catalyst particles can be well dispersed on the support surface and facilitate the construction of a three-phase interface consisting of the catalyst, the reactant water molecule, and the produced oxygen [81]. In fact, this effect has been widely used to explain the increased activity of supported catalysts. For example, Ir nanoparticles can be well dispersed onto the TiN carrier. The IrO\({}_{2}\)@Ir/TiN catalyst prepared by [PERSON]'s group showed an enhanced catalytic performance [50]. The overpotential was only 265 mV at a current density of 10 mA\(\cdot\)cm\({}^{-2}\). [PERSON] et al. synthesized iridium dioxide nanoparticle catalysts with \(\alpha\)-MnO\({}_{2}\) nanorods as supports by a simple two-step hydrothermal method. They found that iridium dioxide nanoparticles were subjected to compressive strain due to the lattice mismatch between IrO\({}_{2}\) and \(\alpha\)-MnO\({}_{2}\) (Figure 3c) [45].