The mechanism of nanocopper synthesis under supercritical water gasification of methanol

This paper studied the effect of diverse parameters (reaction time, precursor concentration and molar ratio of alkali to copper ions) on different sizes of copper particles production. In all experiments, over 99 % of Cu²⁺ is converted to Cu. The results show that under conditions of shorter reaction time (5 min), lower precursor concentration (0.01 M), and ideal molar ratio of alkali to copper ions ([OH⁻]:[Cu²⁺] = 1), copper nanoparticles are produced with good dispersity, and an average diameter of 33.05 ± 9.34 nm. The study proposes a mechanism that involves organic adsorption on the surfaces of copper nuclei. This implies that promoting ligand adsorption on copper nuclei surfaces is key to producing smaller particles, since it limits nanoparticle growth. Furthermore, H₂ and CO both contribute to the reduction of Cu²⁺ to Cu. H₂ serves as the primary reducing agent, from the analysis of gaseous products. The study proposes a mechanism for nanocopper size control.