Nanoporous Mo-Doped NiFe Oxide Nanowires from Eutectic Dealloying as an Active Electrocatalyst for the Alkaline Oxygen Evolution Reaction

Abstract

Developing cost-effective, active, and robust oxygen evolution reaction (OER) electrocatalysts in alkaline electrolytes is a critical problem in the efficient conversion of renewable energy resources. Here, 3D bicontinuous Mo-doped nanoporous NiFe oxide nanowires (Ni1.4Fe1.7Mo0.05O4) fabricated by eutectic solidification and two-step dealloying exhibit an efficient electrocatalytic OER performance. The resultant nanoporous catalyst can achieve an exceptional activity with a low overpotential (205 mV at 10 mA cm–2) and a small Tafel slope (51.3 mV dec–1), outperforming most of the NiFe-based benchmarks. X-ray absorption spectroscopy combined with density functional theory calculations reveals that strong coupling between the Mo–Fe(Ni)–O sites and its remarkable lattice contraction facilitate the electron transfer on the tiny ligament surface, where the high-valent Mo sites can absorb H2O molecules and lower the energy barrier of OOH* for adsorption and activation of H2O. Meanwhile, 1-D nanowire and 3-D bicontinuous nanoporous structures together with the optimized atom ratio of Fe and Ni can accelerate electron/ion transport in the OER process, thus further enhancing the OER performance.

Nanoporous oxide electrodes for energy conversion and storage devices

“…As presented in Fig. 6a, dealloying can be achieved through chemical etching, 3,181–186 electrochemical processing, 181,187–190 immersion in liquid metal, 181,191–193 and solid-state stripping, 181,194–196 as well as by vapor-thermal processing. 181,197–199 The metal atoms in the primary alloy are changed into metallic ions by localized oxidation when nanoporous oxide materials are produced using dealloying procedures.…”

“…6b shows the preparation of nanoporous Ni 1.4 Fe 1.7 Mo 0.05 O 4 nanowires via a two-step chemical dealloying procedure in which the AlNiFeMo alloy was immersed in corrosive solutions. 182 Fig. 6c and d illustrate the SEM and TEM images of the nanoporous Ni 1.4 Fe 1.7 Mo 0.05 O 4 nanowires, which have an average diameter of 200 nm and a length of over 10 μm with an average pore/ligament size of around 4 nm.…”