In Situ Fabrication of Nickel–Iron Oxalate Catalysts for Electrochemical Water Oxidation at High Current Densities

Abstract

Ni–Fe-based electrode materials are promising candidates for the oxygen evolution reaction (OER). The synergy between Fe and Ni atoms is crucial in modulating the electronic structure of the active site to enhance electrochemical performance. Herein, a simple chemical immersion technique was used to grow Ni–Fe oxalate nanowires directly on a porous nickel foam substrate. The as-prepared Ni–Fe oxalate electrode exhibited an excellent electrochemical performance of the OER with ultralow overpotentials of 210 and 230 mV to reach 50 and 100 mA cm–2 current densities, respectively, in a 1 M KOH aqueous solution. The excellent OER performance of this Ni–Fe oxalate electrode can be attributed to its bimetallic composition and nanowire structure, which leads to an efficient ionic diffusion, high electronic conductivity, and fast electron transfer. The overall analysis indicates a suitable approach for designing electrocatalysts applicable in energy conversion.

Electronic structure engineering for electrochemical water oxidation

“…So far, the state-of-the-art IrO 2 and RuO 2 exhibit the best catalytic OER activity, but their low terrestrial availability and high cost limit their use in large scale applications. [22][23][24] Therefore, signicant research has been directed toward developing earth-abundant transition-metal-based electrocatalysts including oxides, layered double hydroxides (LDH), nitrides, suldes, selenides, and perovskite-based materials. [25][26][27][28][29][30][31][32][33][34] The transition-metal-based catalysts proved to have lower cost, higher natural abundance, unique electronic and mechanical properties, and good OER performances.…”

Effect of Iron Concentration and Annealing Conditions on the Catalytic Performance of Co–Mn Spinel Oxides with a Unique Nanowire–Nanosheet Coexisting Structure for Water Oxidation

“…Besides, broad and weak peaks of CoMnFeO 4 result from poor crystallization, high structural disorder, and concentration of active sites. This is possibly beneficial for boosting electrocatalytic performance . In addition, the XRD patterns of CoMnFeO 4 with different Fe contents are also shown in Figure S3a.…”

“…The measured potential was calculated according to the reversible hydrogen electrode (RHE) via the following Nernst equation: E RHE = E Ag/AgCl + 0.197 + 0.059pH. The overpotentials were calibrated via the equation: η = E RHE – 1.23 V. The Tafel slopes were obtained from the equation: η = a + b × log j , where “ a ”, “ b ”, and “ j ” represent constant, Tafel slope, and measured current density, respectively. Frequency under the range of 1 × 10 –1 to 1 × 10 5 Hz was carried out during electrochemical impedance spectroscopy (EIS) measurements.…”

“…Therefore, high-activity, earth-abundant, inexpensive, non-noble elements-based electrocatalysts are seen as potential candidates for water oxidation research. Until now, some success has been achieved with the use of non-precious metal-based catalysts for water oxidation. − This includes spinel transition metal-based oxides (TMO, such as NiMn 2 O 4 , FeCo 2 O 4 , CoMn 2 O 4 , and Co 2 MnO 4 ). For instance, Menezes and co-workers synthesized NiMn 2 O 4 with predesign ratios of Ni/Mn to boost the efficiency of OER .…”

Cobalt-iron oxide/black phosphorus nanosheet heterostructure: Electrosynthesis and performance of (photo-)electrocatalytic oxygen evolution

“…Combining O 1s XPS spectra with Co 2p XPS spectra as well as Fe 2p XPS spectra, it is concluded that Co-O-Fe interfacial species are generated. Electron migration from Fe to Co along the way of O bridge via the interface could effectively regulate the electronic structure, which in turn optimizes the adsorption and enhances electrochemical behavior of Co-Fe/BP [29,30].…”