An Efficient and Earth‐Abundant Oxygen‐Evolving Electrocatalyst Based on Amorphous Metal Borides

Abstract

to the efficiency loss of the overall electrochemical process. [2] Therefore, efficient OER electrocatalyst is a cornerstone for the sustainable energy storage and conversion technologies. [3] Noble-metal-based catalysts such as Ru and Ir oxides have been reported to be excellent OER catalysts; [4] however, their low natural abundance and higher cost render their widespread commercial utilization impractical.[5] Thus, developing efficient, durable, and cost-effective catalytic materials for OER is crucial, but so far still remains a great challenge.Recently, various metal-metalloid compound materials such as chalcogenides, nitrides, and phosphides have been reported to exhibit promising OER electrocatalytic activities. [6] This has been attributed to the charge transfer between different elements and the modified electronic structures, and consequently lowers the kinetic energy barriers of the electrochemical processes. [7] In this regard, to extend such applications on metal borides is reasonable, wherein metal borides share certain properties with other metal-metalloids, such as bonding schema in metal phosphides. [8] Recently, the application of monometallic borides such as cobalt boride, iron boride, and nickel boride as well as cobalt-borate-based graphene hybrid as oxygen-evolving catalyst has been reported to exhibit promising electrocatalytic activity for OER in alkaline media. [9] However, multimetal-metalloid boron-based material, herein referred to as an amorphous quaternary metal boride, for simplicity, as oxygen-evolving electrocatalyst, reported to date is very limited. Thus, it is still of great interest to develop metal-boride-based OER catalysts and further to explore their catalytic activities. The as-identified approach to enhance electrochemical OER properties in metalmetalloid material opens a new avenue in related applications for energy devices that involve OER such as water electrolysis and metal-air batteries.Despite the complicated structure of amorphous material, well-characterized amorphous nanomaterial as oxygen-evolving material has received attention due to the unique properties such as higher catalytic selectivity and activity. [10] A great number of under-coordinated metal atoms, and hence abundant defects, in amorphous nanomaterial may provide more reactive sites at the catalyst surface, and as a result, facilitating the binding of hydroxyls and thus enhancing OER performance. [11] Furthermore, these amorphous nanomaterials have attracted much attention in other electrochemical applications Cost-effective and efficient oxygen-evolving electrocatalysts are urgently required for energy storage and conversion technologies. In this work, an amorphous trimetallic boride nanocatalyst (Fe-Co-2.3Ni-B) prepared by a simple approach is reported as a highly efficient oxygen evolution reaction electrocatalyst. It exhibits an overpotential (η) of 274 mV to deliver a geometric current density (j geo ) of 10 mA cm −2 , a small Tafel slope of 38 mV dec −1 , and excellent long-term durabil...

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