Phase-Controlled Ruthenium Nanocrystals on Colloidal Polydopamine Supports and Their Catalytic Behaviors in Aerobic Oxidation Reactions

HCP-to-FCC Phase Transformation of Ruthenium Nanocrystals Selectively Activate Hydrogen Peroxide for Boosting Peroxidase-like Activity

Due to the simultaneous activation of hydrogen peroxide (H2O2) and oxygen, Ru nanocrystals exhibit inherent peroxidase- and oxidase-like activities, thereby limiting their extensive application in biosensing. Phase engineering of Ru nanocrystals holds great promise for enhancing catalytic activity and selectivity but remains a challenge. Here, highly active Ru nanocrystals with a metastable face-centered cubic (fcc) structure were successfully synthesized via a facile wet-chemical method followed by an etching step, enabling selective activation of H2O2 and demonstrating promising peroxidase-like activity. Compared to the thermodynamically favored hexagonal close-packed Ru nanocrystals, the resultant fcc Ru shows an over 5-fold enhancement in the maximum reaction velocity of the peroxidase-like catalysis, while its oxidase-like performance exhibits a minor decline, indicating a transition from multienzyme activity to specificity. Theoretical calculations reveal that the phase transformation of Ru not only results in an upward shift of the d-band center to enhance H2O2 adsorption but also regulates the O-O bonding strength of H2O2 to achieve selective H2O2 activation. As a proof of concept, a colorimetric sensor based on fcc Ru nanocrystals was successfully constructed, achieving accurate and sensitive detection of organophosphorus pesticides. This work not only offers promising prospects for phase engineering of Ru nanocrystals but also highlights the significance of the Ru phase transition in hydrogen peroxide activation.

Phase control of solid-solution RuIn nanoparticles and their catalytic properties

The properties of solids could be largely affected by their crystal structures. We achieved, for the first time, the phase control of solid-solution RuIn nanoparticles (NPs) from face-centred cubic (fcc) to hexagonal close-packed (hcp) crystal structures by hydrogen heat treatment. The effect of the crystal structure of RuIn alloy NPs on the catalytic performance in the hydrogen evolution reaction (HER) was also investigated. In the hcp RuIn NPs, enhanced HER catalytic performance was observed compared to the fcc RuIn NPs and monometallic Ru NPs. The intrinsic electronic structures of the NPs were investigated by valence-band X-ray photoelectron spectroscopy (VB-XPS). The d-band centre of hcp RuIn NPs obtained from VB-XPS was deeper than that of fcc RuIn NPs and monometallic Ru NPs, which is considered to enable the hcp RuIn NPs to exhibit enhanced HER catalytic performance.