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The structural stability of nanocatalysts during electrochemical CO2 reduction (CO2RR) is crucial for practical applications. However, highly active nanocatalysts often reconstruct under reductive conditions, requiring stabilization strategies to maintain activity. Here, we demonstrate that the N-heterocyclic carbene (NHC) polymer stabilizes Au nanowire (NW) catalysts for selective CO2 reduction to CO over a broad potential range, enabling coupling with Cu NWs for one-step tandem conversion of CO2 to C2H4. By combining the hydrophobicity of the polystyrene chain and the strong binding of NHC to Au, the polymer stabilizes Au NWs and promotes CO2RR to CO with excellent selectivity (>90%) across −0.4 V to −1.0 V (vs RHE), a significantly broader range than unmodified Au NWs (−0.5 V to −0.7 V). Stable CO2RR at negative potentials yields a high jCO of 142 A/g Au at −1.0 V. In situ ATR-IR analysis indicates that the NHC polymer regulates the water microenvironment and suppresses hydrogen evolution at high overpotential. Moreover, NHC-Au NWs maintain excellent stability during 10 h of CO2RR testing, preserving the NW morphology and catalytic performance, while unmodified NWs degrade into nanoparticles with reduced activity and selectivity. NHC-Au NWs can be coupled with Cu NWs in a flow cell to catalyze CO2RR to C2H4 with 58% efficiency and a partial current density of 70 mA/cm2 (overall C2 product efficiency of 65%). This study presents an adaptable strategy to enhance the catalyst microenvironment, ensure stability, and enable efficient tandem CO2 conversion into value-added hydrocarbons. 

We report a new design of polymer phenylacetylene (PA) ligands and the ligand exchange methodology for colloidal noble metal nanoparticles (NPs). PA-terminated poly(ethylene glycol) (PEG) can bind to metal NPs through acetylide (M-CC-R) that affords a high grafting density. The ligand−metal interaction can be switched between σ bonding and extended π backbonding by changing grafting conditions. The σ bonding of PEG−PA with NPs is strong and it can compete with other capping ligands including thiols, while the π backbonding is much weaker. The σ bonding is also demonstrated to improve the catalytic performance of Pd for ethanol oxidation and prevent surface absorption of the reaction intermediates. Those unique binding characteristics will enrich the toolbox in the control of colloidal surface chemistry and their applications using polymer ligands. 

We summarize recent advances in the design of hybrid nanostructures through the combination of synthetic polymers and plasmonic nanoparticles (NPs). We categorize the synthetic methods of those polymer-coated metal NPs into two main strategies: direct encapsulation and chemical grafting, based on how NPs interact with polymers. In direct encapsulation, NPs with hydrophobic ligands are physically encapsulated into polymer micelles, primarily through hydrophobic interactions. We discuss strategies for controlling the loading numbers and locations of NPs within polymer micelles. On the other hand, polymer-grafted NPs (PGNPs) have synthetic polymers as ligands chemically grafted on NPs. We highlight that polymer ligands can asymmetrically coat metal NPs through hydrophobicity-driven phase segregation using homopolymers, BCPs and blocky random copolymers. This review provides insights into the methodologies and mechanisms to design new nanostructures of polymers and NPs, aiming to enhance the understanding of this rapidly evolving field. 

We report a facile method to prepare polymer-grafted plasmonic metal nanoparticles (NPs) that exhibit pH-responsive surface-enhanced Raman scattering (SERS). The concept is based on the use of pH- responsive polymers, such as poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH), as multi- dentate ligands to wrap around the surface of NPs instead of forming polymer brushes. Upon changing the solvent quality, the grafted pH-responsive polymers would drive reversible aggregation of NPs, leading to a decreased interparticle distance. This creates numerous hot spots, resulting in a secondary enhancement of SERS as compared to the SERS from discrete NPs. For negatively charged PAA-grafted NPs, the SERS response at pH 2.5 showed a secondary enhancement of up to 104-fold as compared to the response for discrete NPs at pH 12. Similarly, positively charged PAH-grafted AuNPs showed an oppo- site response to pH. We demonstrated that enhanced SERS with thiol-containing and charged molecular probes was indeed from the pH-driven solubility change of polymer ligands. Our method is different from the conventional SERS sensors in the solid state. With pH-responsive polymer-grafted NPs, SERS can be performed in solution with high reproducibility and sensitivity but without the need for sample pre-con- centration. These findings could pave the way for innovative designs of polymer ligands for metal NPs where polymer ligands do not compromise interparticle plasmon coupling. 

We report the use of polymer N -heterocyclic carbenes (NHCs) to control the microenvironment surrounding metal nanocatalysts, thereby enhancing their catalytic performance in CO 2 electroreduction. Three polymer NHC ligands were designed with different hydrophobicity: hydrophilic poly(ethylene oxide) (PEO–NHC), hydrophobic polystyrene (PS–NHC), and amphiphilic block copolymer (BCP) (PEO- b -PS–NHC). All three polymer NHCs exhibited enhanced reactivity of gold nanoparticles (AuNPs) during CO 2 electroreduction by suppressing proton reduction. Notably, the incorporation of hydrophobic PS segments in both PS–NHC and PEO- b -PS–NHC led to a twofold increase in the partial current density for CO formation, as compared to the hydrophilic PEO–NHC. While polymer ligands did not hinder ion diffusion, their hydrophobicity altered the localized hydrogen bonding structures of water. This was confirmed experimentally and theoretically through attenuated total reflectance surface-enhanced infrared absorption spectroscopy and molecular dynamics simulation, demonstrating improved CO 2 diffusion and subsequent reduction in the presence of hydrophobic polymers. Furthermore, NHCs exhibited reasonable stability under reductive conditions, preserving the structural integrity of AuNPs, unlike thiol-ended polymers. The combination of NHC binding motifs with hydrophobic polymers provides valuable insights into controlling the microenvironment of metal nanocatalysts, offering a bioinspired strategy for the design of artificial metalloenzymes.