Flame synthesis achieves compositionally tailorable high-entropy metal-containing nanomaterials.

High-entropy metal-containing nanomaterials have garnered interest in diverse fields such as electrocatalysis and energy conversion. Their synthesis typically requires high temperatures (>1,000 K) to facilitate homogeneous mixing and rapid transformation of metal precursors. However, current state-of-the-art approaches typically involve complex reaction environments and require specialized equipment and operations. Herein we demonstrate a versatile flame synthesis process to fabricate high-entropy metallic single atoms and/or nanoparticles supported on soot-like carbon via blending organometallic precursors into fuel (namely, paraffin wax) and subsequent burning. The high flame temperature (~1,800 K) enables strong metal-carbon association with tailorable chemistry and homogeneous bonding between dissimilar metallic elements (up to 25 metals studied), regardless of their thermodynamic compatibility. Additionally, we show high-performance electrosynthesis of hydrogen peroxide to highlight this approach as a promising method for electrocatalyst development.