Comparative Study on Hydrogen Evolution Reaction Activity of Electrospun Nanofibers with Diverse Metallic Ir and IrO₂ Composition Ratios

Abstract

Hydrogen evolution reaction (HER) is of importance in energy conversion processes. This paper reports the facile synthesis of iridium/iridium oxide nanofibers (Ir/IrO2NFs) with diverse Ir and IrO2 relative composition ratios and their electrocatalytic HER activities. Highly porous Ir/IrO2NFs are simply synthesized via electrospinning and the following calcination at various temperatures (300–900 °C). Different calcination temperature alters the actual composition of Ir/IrO2NFs: The higher the temperature, the greater IrO2 content exists. The HER activity of Ir/IrO2NFs is examined in 1 M H2SO4. Ir/IrO2NF calcined at 300 °C exhibits the best HER activity in terms of the onset potential, overpotential generating 50 mA cm–2, turnover frequency, Tafel slope along with the decent stability for 5 h; the HER performance of this material even exceeds that of platinum, a benchmark HER catalyst. As the IrO2 content in Ir/IrO2NFs increases with a higher calcination temperature, the HER activity decreases. Ir/IrO2NF calcined at 900 °C consists of only IrO2 and presents the worst activity. DFT calculations show that hydrogen atom adsorption on metallic Ir (not IrO2) resembles that on Pt: similar adsorption energy and adsorbate–substrate distance. Both the experimental and theoretical results clearly demonstrate that metallic Ir rather than IrO2 is a good HER catalytic platform.

Oxide Electrocatalysts Based on Earth-Abundant Metals for Both Hydrogen- and Oxygen-Evolution Reactions

“…For hydrogen-evolution reaction (HER), the high cost of platinum used in the Pt/C catalyst − and some of the Ir-based alternatives has led to the investigation of various other catalysts such as sulfides, phosphides, carbides, and nitrides . However, oxides, particularly perovskite oxides, with good HER activity in either acidic or basic condition are not very common.…”

Electronic modulation and interface engineering of electrospun nanomaterials‐based electrocatalysts toward water splitting

“…In addition to the interface at CNF/acitive catalyst, the interface between metal and semiconductor to construct a heterostructure plays a key role in the improvement of HER performance 113‐119 . Our group has developed a simple electrospinning strategy combined with pyrolysis process to prepare Mo/Mo 2 C/CNFs hybrid electrocatalyst for HER 118 .…”

“…112 In addition to the interface at CNF/acitive catalyst, the interface between metal and semiconductor to construct a heterostructure plays a key role in the improvement of HER performance. [113][114][115][116][117][118][119] Our group has developed a simple electrospinning strategy combined with pyrolysis process to prepare Mo/Mo 2 C/CNFs hybrid electrocatalyst for HER. 118 By using bis(acetylacetonato)dioxomolybdenum as the Mo precursor and the introduction of cellulose as the carbon source, a distinct metal-semiconductor interface was achieved.…”

Coaxial nanofibers of nickel/gadolinium oxide/nickel oxide as highly effective electrocatalysts for hydrogen evolution reaction

“…Nickel oxide can be used in advanced technologies depending on its synthesis conditions and microstructures [9][10][11][12][13][14][15][16]. Many routes have been successfully applied to fabricate different NiO morphologies, including precipitation methods [17], hydrothermal [18,19], solvothermal [20,21], microemulsion [22,23], oxidation of metallic Ni [24], thermal decomposition of Ni(II)-metalloorganic [25] and electrospinning [26][27][28][29][30][31]. Among these methods, the electrospinning has turned out to be a preferable choice because of its simplicity and scalability to yield nanofibers at an industrial level, and easy control over the morphology of the nanofibers [32][33][34][35][36][37][38][39][40].…”