α-MnO2 作为先进的双功能ORR/IOR电催化剂构建可充电锌空电池

α-MnO2 as an advanced bifunctional ORR/IOR electrocatalyst for Zn-air battery

  • 摘要: 析氧反应(oxygen evolution reaction, OER)和氧还原反应(oxygen reduction reaction, ORR)是可充电锌空电池(rechargeable Zn-air batteries, RZABs)重要的两个反应。其中,析氧反应具有较高的热力学平衡电位和复杂的反应路径,实际应用中需要高的充电电压驱动其发生,这将带来一系列问题并且限制了RZABs的商业化应用。基于此,本研究构造α-MnO2并作为ORR/IOR双功能催化剂。在碱性体系中引入反应改性剂KI,α-MnO2对碘离子氧化反应(iodide oxidation reaction, IOR)具有更低的阳极氧化电位和更快的催化动力学。当1.0 mol/L KOH电解液中添加0.5 mol/L KI时,相比于OER(1.709 V @10 mA/cm2),α-MnO2在IOR过程中电流密度达到10 mA/cm2时阳极电位减小了398 mV(1.311 V vs. RHE),且表现出低至57.5 mV/dec塔菲尔斜率。相对于与Pt/C,在含有KI的KOH电解液中,α-MnO2表现出与Pt/C相媲美的ORR活性。此外,以α-MnO2为空气电极组装成RZAB后,该电池也表现出了优异的充电活性和良好的循环寿命,在5 mA/cm2电流密度下,充放电电压间隙由0.97 V缩减为0.61 V,能量转换效率由54.9%提升至66.2%。

     

    Abstract: Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are important reactions for rechargeable Zinc-air batteries (RZABs). Unfortunatly, OER holds a high thermodynamic equilibrium potential and complex reaction path, which require an large votage to derive this reaction and greatly hinder its commercial application. Herein, α-MnO2 was successfully achieved and as the bifunctional ORR/iodide oxidation reaction (IOR) electrocatalyst. In alkline media, α-MnO2 exhibits fast kinetics and low oxidation potential for IOR. Expectedly, α-MnO2 exhibits remarkable IOR activity in 1.0 mol/L KOH with 0.5 mol/L KI. Compared with potential at 10 mA/cm2 for OER (1.709 V vs. RHE), the potential at 10 mA/cm2 reduce 398 mV (1.311 V vs. RHE) for α-MnO2 during IOR process. α-MnO2 also provides small Tafel slope of 57.5 mV/dec. Additionly, α-MnO2 represents outsanding ORR performances with respect to Pt/C. As an air electrode for RZAB, the fabricated RZAB delivers excellent performances. To be specific, at 5 mA/cm2, the voltage gap between charging and discharging reduces from 0.97 V to 0.61 V, energy efficiency increses from 54.9% to 66.2%. This work provide an unique strategy to construct bifunction ORR/IOR electrocatalysts and promote the commercialization of RZABs.

     

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