Autocatalytic Reduction in the Synthesis of Multimetallic Nanocrystals: Mechanisms and Opportunities

Autocatalytic reduction enables multimetallic nanocrystal synthesis by turning nascent metal surfaces into catalytic platforms that accelerate precursor conversion and couple reduction directly to deposition. This review consolidates the mechanistic basis of autocatalytic reduction and distills it into practical design rules for alloying and high‐entropy phase formation. We summarize key kinetic signatures, including induction periods, rate acceleration, and pathway switching between homogeneous solution reduction and surface‐mediated reduction, and relate them to nucleation and growth frameworks such as LaMer‐type supersaturation, heterogeneous nucleation and seeded growth, and the Finke–Watzky two‐step model separating slow nucleation from autocatalytic growth. We then examine bottlenecks in multimetallic synthesis, particularly precursor mismatch, and discuss how autocatalysis biases reduction toward catalytic surfaces to narrow kinetic disparities and promote atomic mixing toward single‐phase solid solutions. Representative case studies illustrate how temperature programming, precursor selection, and thermal treatments regulate coupled reduction, nucleation, growth, and diffusion to access well‐defined multimetallic nanocrystals. We also outline characterization strategies combining in situ spectroscopy or hydrogen temperature‐programmed reduction with microscopy and composition analysis. Finally, we outline four outlook directions centered on quantitative kinetic frameworks, non‐precious autocatalytic surfaces, surface‐state engineering, and diffusion‐aware processing strategies, aimed at enabling scalable and reproducible synthesis of multimetallic nanocrystals.