Nanoporous Al‐Ni‐Co‐Ir‐Mo High‐Entropy Alloy for Record‐High Water Splitting Activity in Acidic Environments

Abstract

Ir‐based binary and ternary alloys are effective catalysts for the electrochemical oxygen evolution reaction (OER) in acidic solutions. Nevertheless, decreasing the Ir content to less than 50 at% while maintaining or even enhancing the overall electrocatalytic activity and durability remains a grand challenge. Herein, by dealloying predesigned Al‐based precursor alloys, it is possible to controllably incorporate Ir with another four metal elements into one single nanostructured phase with merely ≈20 at% Ir. The obtained nanoporous quinary alloys, i.e., nanoporous high‐entropy alloys (np‐HEAs) provide infinite possibilities for tuning alloy's electronic properties and maximizing catalytic activities owing to the endless element combinations. Particularly, a record‐high OER activity is found for a quinary AlNiCoIrMo np‐HEA. Forming HEAs also greatly enhances the structural and catalytic durability regardless of the alloy compositions. With the advantages of low Ir loading and high activity, these np‐HEA catalysts are very promising and suitable for activity tailoring/maximization.

Design of Complex Solid‐Solution Electrocatalysts by Correlating Configuration, Adsorption Energy Distribution Patterns, and Activity Curves

“…[4] Optimization of the composition allows for increasing the number of active sites with favorable adsorption energy for the reaction of interest, and thus,t he optimal choice of elements and their respective ratio can generate very active catalysts as long as aC SS phase is formed. Thes uccessful use of CSSs as electrocatalysts for several reactions,s uch as ammonia synthesis, [5] CO oxidation, [6] CO 2 reduction, [7] the ORR, [6,8] hydrogen evolution reaction (HER), [9][10][11] or the OER [9,11,12] was shown confirming universal applicability.H owever,t he complex underlying working principles are still widely unknown with al ack of ac onceptual framework. Hence,i ndepth understanding is required to tailor new catalysts for specific reactions.A djusting of the activity of ORR catalysts was shown experimentally by tailoring the CSS composition, [8] astrategy which could be rationalized by atheoretical study of the adsorption energy distribution pattern (AEDP) [4] and its implication on the specific electrochemical behavior.…”

Fast Site-to-site Electron Transfer of High-entropy Alloy Nanocatalyst Driving Redox Electrocatalysis

“…2c), the content of Ni 0 is lower than the content of Ni 2+ because of the high chemical activity of Ni. 28,29 The Fe 2p spectra in Supplementary Fig. 2d shows two peaks at 711.6 eV and 724.8 eV, which can be attributed to Fe 2p 3/2 and Fe 2p 1/2 , respectively.…”

“…[23][24][25] Recently, some HEAs had used as catalysts for electrocatalytic reactions, which display superior stability and catalytic selectivity and activity compared with traditional alloys. 13,[26][27][28][29][30] However, the traditional method mainly produce bulk HEAs rather than nanostructures. 26,[31][32][33][34] Moreover, the preparation of uniform nanostructured HEAs with small size (< 10 nm) currently requires speci c equipment (fast heating/cooling rate, ~10 5 K per second), high temperature (~2000 kelvin), and high temperature resistant and conductive substrate (carbon nano ber), such as carbon-thermal shock method.…”

Nano High‐Entropy Materials: Synthesis Strategies and Catalytic Applications

“…[16] A series of HEMs such as CrMnFeCoNi HEA, (NiMgCuZnCo)O HEO, and (CrMoNbVZr)N HEN have been successfully developed in this field. [11,17,18] Containing five or even more metals, the unique chemical and physical complexities provide HEMs tailorable phase structure and atom configuration, making HEMs an ideal platform for advanced catalysis. In the conventional binary or ternary alloy systems, the catalytic performance is predominantly determined by the principal component, whereas the doped elements slightly affect its properties.…”