Hydrogen production
via electrocatalytic water splitting has attracted
growing attention as an alternative renewable and clean energy source.
Size-specific gold nanoclusters and complexes (AuNCs) can serve as
models for investigating the catalytic behavior toward the hydrogen
evolution reaction (HER) at the atomic level. This work is focused
on exploring the factors influencing the catalytic activity of phosphine-ligated
AuNCs as electrocatalysts for improving HER performance using Au101(PPh3)21Cl5, Au9(PPh3)8(NO3)3, and Au1(PPh3)Cl supported on reduced graphene oxide (rGO).
Production of AuNC–rGO nanocomposites without agglomeration
of the AuNCs was confirmed by transmission electron microscopy, X-ray
photoelectron spectroscopy, and visible light absorbance. The weight
loading of gold in the nanocomposite material was confirmed to be
≈5 wt % by thermogravimetric analysis and inductively coupled
plasma mass spectrometry. Electrocatalytic performance of the AuNCs
was determined through linear sweep voltammograms in 0.5 M sulfuric
acid. Greater performance was observed for Au101NC–rGO,
while Au9NC–rGO and Au1NC–rGO
showed similar performance. The stability of each AuNC was determined
through extended chronoamperometry experiments, and negligible reduction
in performance was observed for Au101NC–rGO and
Au9NC–rGO, while Au1NC–rGO was
less stable. The variation in performance was attributed to a range
of factors including catalyst size, electronic structure, and ligand
density. This work provides guidelines to design highly efficient
electrocatalysts using ligated metal clusters.
The development of a stable and efficient Oxygen Reduction Reaction (ORR) electrocatalysts with high methanol tolerance is crucial for Direct Methanol Fuel Cells (DMFCs). Herein, triphenylphosphine (PPh 3 )-ligated gold nanoclusters and complexes (AuNCs), Au 101 (PPh 3 ) 21 Cl 5 , Au 9 (PPh 3 ) 8 (NO 3 ) 3 , and Au 1 (PPh 3 )Cl supported on reduced graphene oxide (rGO) have been explored as methanol tolerant ORR electrocatalysts. Electrocatalytic performance of each AuNCs-rGO was determined through linear sweep voltammograms (LSV) and cyclic voltammetry (CV) and compared with Pt/C. Sizedependent ORR activity was observed which followed the size trend of Au 101 NC-rGO > Au 9 NC-rGO > Au 1 NC-rGO. Repeated LSV and chronoamperometry measurements revealed that the long-term stability over 24 hours followed the trend Au 101 NC-rGO > Au 9 NC-rGO ~Au 1 NC-rGO and all were more stable than Pt/C. The methanol tolerance of each AuNCs-rGO was also evaluated via LSV and CV. Size-independent methanol tolerance with no noticeable change in ORR performance of AuNCs-rGO was observed in the presence of methanol. AuNCs-rGO nanocomposites are promising cathode electrocatalysts for DMFCs.
Herein, the UV light photocatalytic activity of an Au101NC-AlSrTiO3-rGO nanocomposite comprising 1 wt% rGO, 0.05 wt% Au101(PPh3)21Cl5 (Au101NC), and AlSrTiO3 evaluated for H2 production. The synthesis of Au101NC-AlSrTiO3-rGO nanocomposite followed two distinct routes: (1) Au101NC was first mixed with AlSrTiO3 followed by the addition of rGO (Au101NC-AlSrTiO3:rGO) and (2) Au101NC was first mixed with rGO followed by the addition of AlSrTiO3 (Au101NC-rGO:AlSrTiO3). Both prepared samples were annealed in air at 210 °C for 15 min. Inductively coupled plasma mass spectrometry and high-resolution scanning transmission electron microscopy showed that the Au101NC adhered almost exclusively to the rGO in the nanocomposite and maintained a size less than 2 nm. Under UV light irradiation, the Au101NC-AlSrTiO3:rGO nanocomposite produced H2 at a rate 12 times greater than Au101NC-AlSrTiO3 and 64 times greater than AlSrTiO3. The enhanced photocatalytic activity is attributed to the small particle size and high loading of Au101NC, which is achieved by non-covalent binding to rGO. These results show that significant improvements can be made to AlSrTiO3-based photocatalysts that use cluster co-catalysts by the addition of rGO as an electron mediator to achieve high cluster loading and limited agglomeration of the clusters.
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