Synthesis of Free-Standing Spinel FeCo2S4 Nanoplates toward Improvement of Electrocatalytic Oxygen Evolution from Water Splitting

Ching-Wen Liao | Academia Sinica | Taipei, Taiwan

Abstract

In this work, a system of FeCo2S4-catalyzed oxygen evolution reaction (OER) is studied. The spinel FeCo2S4 nanocatalyts are synthesized by a two-step hydrothermal method on a Ni foam (NF) by vulcanizing Fe-Co precursors with different [Na2S], leading to the products of excavated nanospheres (ENSs). Besides, the structures of FeCo2S4 ENSs are stable after 12-hour OER durability test. Only the surface states of them are changed largely due to drastic leaching of sulfur. The phenomenon implies sulfur a key role on the surface instead of in the structure of an ENS for OER. In the results of potential-dependent XRD and XAS with the 0.1 M-FeCo2S4/NF electrode, the dominant pathway for FeCo2S4-catalyzed water splitting is via the formation of MOOH followed by release of O2. Hence, the reason of S-assisted OER is due to optimization of conductivity to benefit the MOOH generation. This finding which was presented in few reports is now bringing a proof to confirm the absence of MSOH during the OER.

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