Large-scale and facile synthesis of a porous high-entropy alloy CrMnFeCoNi as an efficient catalyst

Abstract

High-entropy alloys (HEAs) have exhibited large potential to serve as excellent heterogeneous catalysts in a variety of reactions. Although several synthetic procedures have been reported, developing novel routes to facilely prepare HEA-based catalysts is still urgently desired, especially for large-scale preparation. Herein, we successfully prepared porous HEAs by directly etching low-cost, accessible, and commercial HEA powders in an acid aqueous solution at room temperature. Porous HEA CrMnFeCoNi (CMFCN-4) was synthesized from commercial CrMnFeCoNi powder (the Cantor alloy). Surprisingly, the contents of metallic elements in CMFCN-4 were all maintained at ca. 20% due to a kinetically controlled etching process. In the hydrogenation of p-nitrophenol, porous CMFCN-4 exhibited remarkable catalytic activity by converting >90% of p-nitrophenol into p-aminophenol within 30 min at 25 °C. The activation energy for CMFCN-4 was as low as 31.8 kJ mol⁻¹, even comparable to that for noble-metal based catalysts. Moreover, CMFCN-4 also revealed excellent catalytic stability by preserving nearly 100% of the initial catalytic activity after five successive reaction rounds. Derived from porous structures, the high surface area and exposed high-index facets with terraces contributed to the excellent catalytic performance of CMFCN-4. This work not only provides a highly active and stable HEA-based catalyst, but also opens up a new avenue to the facile and large-scale synthesis of porous HEAs by directly etching commercial HEA powders.