Reducing the noble-metal loading without sacrificing the catalytic performance of the oxygen evolution reaction (OER) catalysts is paramount yet highly challenging. Herein, IrO2@Ir/TiN electrocatalysts employing TiN as the support have been developed and shown high efficiency toward OER. TiN is found not only to disperse the IrO2@Ir nanoparticles effectively but also to exert the electronic modulation of Ir by downshifting its d-band center of 0.21 eV compared to pure IrO2. Excitingly, TiN remarkably enhances the catalytic performance of Ir, where the overpotential to achieve the current density of 10 mA cm–2 is only 265 mV for the IrO2@Ir/TiN (60 wt %) catalyst. As a result, 71.7 wt % of the Ir metal can be saved to compare with the commercial Ir-black counterpart. Moreover, TiN can inhibit the aggregation and oxidative dissolution of Ir species, thereby enhancing the operational stability. The combined advantages of TiN open a new solution to reduce the anodic catalyst cost through boosting the catalytic activity and stability.
Xiucheng Sun,Jian Lin,Yuehan Wang,Lin Li,Xiaoli Pan,Yang Su,Xiaodong Wang
Inert substrate supported Ir catalyst for room-temperature oxidation of formaldehyde has never been reported so far. Here, a novel Ir-based catalyst supported on commercial γ-Al 2 O 3 (IrAl-CD), which was synthesized via a modified colloid-deposition method, can realize complete conversion of HCHO at 20 °C for the first time. It exhibits a two-fold higher specific rate than IrAl-DP prepared by a conventional deposition-precipitation method. Detailed characterizations demonstrate that the positive Ir species bonded with OH groups on IrAl-DP make HCHO oxidation follow a reaction pathway between OH and formate intermediates. In contrast, the fairly high content of metallic Ir 0 species on IrAl-CD facilitates the direct dehydrogenation of HCHO to form the dominant intermediates of CO, which are easily oxidized with a lower activation energy. Consequently, the electronic state of Ir determines the extremely high performance even supporting on inert substrate and the reaction mechanism for HCHO oxidation at ambient temperature.
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