High-entropy alloy electrocatalysts for key reduction reactions, from site statistics to design rules

초록

Electrochemical reduction reactions connect renewable electricity with hydrogen, carbon products, and ammonia-related chemistry, but catalyst design remains difficult because activity, selectivity, and durability require different binding strengths and because active surfaces can reconstruct under bias. High-entropy alloys (HEAs) and related multi-principal-element catalysts address this challenge by providing statistical populations of surface motifs rather than a single averaged active site. This Review discusses HEA and HEA-derived electrocatalysts for the hydrogen evolution reaction (HER), carbon dioxide reduction reaction (CO2RR), nitrogen reduction reaction (NRR), and nitrate reduction reaction (NO3RR), with emphasis on synthesis, theory, operando characterization, benchmarking, and data-driven discovery. Three conclusions emerge. First, HEA design should be expressed in terms of motif probabilities, adsorption-energy distributions, and near-optimal site fractions, because rare local environments can control macroscopic activity and selectivity. Second, catalyst architecture and active-state chemistry must be considered together: synthesis route, phase purity, porosity, compositional gradients, and operando segregation determine the motif distribution sampled during reaction. Third, rigorous benchmarking is essential. Matched low-entropy controls, surface-sensitive composition analysis, per-site activity metrics, and dissolution-aware durability tests are needed to distinguish entropy-enabled effects from conventional alloying or reconstruction. We conclude with design rules and a reporting checklist covering composition verification, operando site mapping, stability analysis, and nitrogen accounting. These practices can help convert chemical disorder in HEAs into reproducible design principles for multi-site electrocatalysis.

키워드