Gold nanoclusters as electrocatalysts: size, ligands, heteroatom doping, and charge dependences

Abstract

To establish an ultimate energy conversion system consisting of a water-splitting photocatalyst and a fuel cell, it is necessary to further increase the efficiencies of the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), and the oxygen reduction reaction (ORR). Recently, it was demonstrated that thiolate (SR)-protected gold clusters, Au n (SR) m , and their related alloy clusters can serve as model catalysts for these three reactions. However, as the previous data have been obtained under different experimental conditions, it is difficult to use them to gain a deep understanding of the means to attain higher activity in these reactions. Herein, we measured the HER, OER, and ORR activities of Au n (SR) m and alloy clusters containing different numbers of constituent atoms, ligand functional groups, and heteroatom species under identical experimental conditions. We obtained a comprehensive set of results that illustrates the effect of each parameter on the activities of the three reactions. Comparison of the series of results revealed that decreasing the number of constituent atoms in the cluster, decreasing the thickness of the ligand layer, and substituting Au with Pd improve the activities in all reactions. Taking the stability of the cluster into consideration, [Au 24 Pd(PET) 18 ] 0 (PET = 2-phenylethanethiolate) can be considered as a metal cluster with high potential as an HER, OER, and ORR catalyst. These findings are expected to provide clear design guidelines for the development of highly active HER, OER, and ORR catalysts using Au n (SR) m and related alloy clusters, which would allow realization of an ultimate energy conversion system. † Electronic supplementary information (ESI) available: Geometrical structure of each cluster, MALDI mass spectra, UV-vis spectra, schematic of the proposed energy conversion system, additional linear sweep voltammograms of the products. See

Creation of active water-splitting photocatalysts by controlling cocatalysts using atomically precise metal nanoclusters

“…If we would design and create appropriate metal NCs based on the attained information, great enhancement of the water-splitting activities of the photocatalysts could be achieved. 78 The metal NCs can be synthesized with atomic precision using thiolate (SR), 21, selenolate (SeR), [115][116][117][118][119][120][121][122] phosphine (PR 3 ), alkyne (C≡CR), 123,124 carbon monoxide (CO), dendrimer, 125 etc. as protective ligands.…”

“…The energy conversion system shown in Figure 1 is one of the ultimate systems for constructing such a society. 2 In this system, hydrogen (H 2 ) is produced by a photocatalyst 3 and/or an electrolysis cell [4][5][6][7][8][9][10][11][12][13][14][15] , and the obtained H 2 is converted into electric power by a fuel cell [16][17][18][19][20][21][22][23][24] . With such a system, it is possible to obtain energy from water and sunlight, which are almost infinite on the earth.…”

Controlled colloidal metal nanoparticles and nanoclusters: recent applications as cocatalysts for improving photocatalytic water-splitting activity

“…239 Thus, spectroscopy, SPM, and DFT calculations are powerful tools for elucidating the phenomenon occurred at the interface of NPs/NCs-photocatalysis. In addition to these methods, electrochemical measurements are also useful for predicting the appropriate cocatalysts 121,122,244 because the overpotential obtained by electrochemical measurements are strongly related to the activation energy of each reaction. At present, these measurements and analyses have not been necessarily conducted for the photocatalysts described in Section 4.…”

Dynamics of Pd Dopant Atoms inside Au Nanoclusters during Catalytic CO Oxidation

“… 8 , 26 , 28 , 29 In addition, the reactivity in catalytic reactions was also altered, 6 and in several cases, doped M 1 Au 24 (M = Pd, Pt, Cd) clusters performed superior in comparison to their homogold analogues. 26 , 28 − 32 …”