Debnath Bharati, Parvin Sahanaz, Dixit Harsha, Bhattacharyya Sayan
Department of Chemical Sciences and Centre for Advanced Functional Materials, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, 741246, India.
ChemSusChem. 2020 Aug 7;13(15):3875-3886. doi: 10.1002/cssc.202000932. Epub 2020 Jun 25.
The scope of any metal oxide as a catalyst for driving electrocatalytic reactions depends on its electronic structure, which is correlated to its oxygen-defect density. Likewise, to transform a spinel oxide, such as cobalt ferrite (CoFe O ), into a worthy universal-pH, bifunctional electrocatalyst for the hydrogen and oxygen evolution reactions (HER and OER, respectively), oxygen defects need to be regulated. Prepared by coprecipitation and inert calcination at 650 °C, CoFe O nanoparticles (NPs) require 253 and 300 mV OER overpotentials to reach current densities of 10 and 100 mA cm , respectively, if nickel foam is used as a substrate. With cost-effective carbon fiber paper, the OER overpotential increases to 372 mV at 10 mA cm at pH 14. The NPs prepared at 550 °C require HER overpotentials of 218, 245, and 314 mV at -10 mA cm in alkaline, acidic, and neutral pH, respectively. The intrinsic activity is reflected from turnover frequencies of >3 O s and >5 H s at overpotentials of 398 and 259 mV, respectively. If coupled for overall water splitting, the extremely durable two-electrode electrolyzer requires a cell potential of only 1.63 V to reach 10 mA cm at pH 14. The homologous couple also splits seawater at impressively low cell voltages of 1.72 and 1.47 V at room temperature and 80 °C, respectively.
任何金属氧化物作为驱动电催化反应催化剂的适用范围取决于其电子结构，而电子结构与其氧缺陷密度相关。同样，要将尖晶石氧化物，如钴铁氧体（CoFe₂O₄）转化为适用于全pH值的、用于析氢反应和析氧反应（分别为HER和OER）的双功能电催化剂，就需要调节氧缺陷。通过共沉淀法制备并在650°C下进行惰性煅烧，若以泡沫镍为基底，CoFe₂O₄纳米颗粒（NPs）分别达到10和100 mA cm⁻²的电流密度时，析氧过电位需要253和300 mV。使用具有成本效益的碳纤维纸时，在pH值为14、电流密度为10 mA cm⁻²的条件下，析氧过电位增加到372 mV。在550°C下制备的NPs在碱性、酸性和中性pH值条件下，于-10 mA cm⁻²时的析氢过电位分别为218、245和314 mV。本征活性分别由在398和259 mV过电位下大于3 O₂ s⁻¹和大于5 H₂ s⁻¹的转换频率反映出来。如果用于全解水，这种极其耐用的双电极电解槽在pH值为14、电流密度为10 mA cm⁻²时仅需1.63 V的电池电位。该同源耦合体系在室温及80°C下分别以低至1.72和1.47 V的电池电压分解海水。
