The Remarkable Rise in High-Entropy Catalysts: A New Paradigm for Sustainable Hydrogen Production.

The hydrogen evolution reaction (HER) is a cornerstone of green hydrogen production, yet its efficiency is constrained by the sluggish kinetics of water splitting. High-entropy catalysts (HECs), single-phase materials incorporating multiple principal elements, have emerged as a transformative solution. Their unique attributes including vast compositional flexibility, tunable electronic structures, and synergistic multi-element interactions, enable them to overcome the activity, stability, and cost limitations of conventional catalysts. Despite rapid performance advancements, the rational design of HECs is fundamentally hampered by critical knowledge gaps, particularly in identifying true active sites under operando conditions and predicting long-term stability. This work critically assesses these challenges, systematically summarizing the latest progress in HECs design, synthesis, and structure-activity relationships. By bridging fundamental principles with practical applications, we provide a forward-looking perspective on key research directions. Distinct from recent progress-focused reviews, this work establishes a strategic roadmap by systematically diagnosing seven grand challenges across the science-to-technology pipeline and proposing corresponding countermeasures. This framework aims to guide future research efforts toward the rational design and practical deployments of HECs for practical and cost-effective green hydrogen production.