<i>In Situ</i> Precise Tuning of Bimetallic Electronic Effect for Boosting Oxygen Reduction Catalysis.

Zhang, Junming; Xu, Weichang; Liu, Yuan; Hung, Sung-Fu; Liu, Wei; Lam, Zhenhui; Tao, Hua Bing; Yang, Hongbin et al. · Nano Lett · 2021

basic_science · Level V

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Abstract

Tuning intermediate adsorption energy by shifting the d-band center offers a powerful strategy to tailor the reactivity of metal catalysts. Here we report a potential sweep method to grow Pd layer-by-layer on Au with the capability to <i>in situ</i> measure the surface structure through an ethanol oxidation reaction. Spectroscopic characterizations reveal charge-transfer induced valence band restructuring in the Pd overlayer, which shifts the d-band center away from the Fermi level compared to bulk Pd. Precise overlayer control gives the optimal bimetallic surface of two monolayers (ML) Pd on Au, which exhibits more than 370-fold mass activity enhancement in oxygen reduction reaction (at 0.9 V vs. reversible hydrogen electrode) and 40 mV increase in half-wave potential compared to the Pt/C. Tested in a homemade Zn-air battery, the 2-ML-Pd/Au/C exhibits a maximum power density of 296 mW/cm<sup>2</sup> and specific activity of 804 mAh/g<sub>Zn</sub>, much higher than Pt/C with the same catalyst loading amount.