期刊
ACS NANO
卷 7, 期 7, 页码 5808-5817出版社
AMER CHEMICAL SOC
DOI: 10.1021/nn400772s
关键词
palladium; subnanometer clusters; nanocrystalline diamond; hybrid nanostructures; nanoparticles; catalysis; electrocatalysis; water oxidation; water splitting; X-ray absorption; GIXAS; GIXAFS; X-ray scattering GISAXS
类别
资金
- U.S. Department of Energy, BES Materials Sciences [DE-AC-02-06CH11357]
- UChicago Argonne, LLC
- U.S. DOE [DE-AC02-06CH11357]
- DOE
- University of Birmingham North America
Water oxidation is a key catalytic step for electrical fuel generation. Recently, significant progress has been made in synthesizing electrocatalytic materials with reduced overpotentials and increased turnover rates, both key parameters enabling commercial use in electrolysis or solar to fuels applications. The complexity of both the catalytic materials and the water oxidation reaction makes understanding the catalytic site critical to improving the process. Here we study water oxidation in alkaline conditions using size-selected clusters of Pd to probe the relationship between cluster size and the water oxidation reaction. We find that Pd-4 shows no reaction, while Pd-6 and Pd-17 deposited clusters are among the most active (in terms of turnover rate per Pd atom) catalysts known. Theoretical calculations suggest that this striking difference may be a demonstration that bridging Pd-Pd sites (which are only present in three-dimensional clusters) are active for the oxygen evolution reaction in Pd6O6. The ability to experimentally synthesize size-specific dusters allows direct comparison to this theory. The support electrode for these investigations is ultrananooystalline diamond (UNCD). This material is thin enough to be electrically conducting and is chemically/electrochemically very stable. Even under the harsh experimental conditions (basic, high potential) typically employed for water oxidation catalysts, UNCD demonstrates a very wide potential electrochemical working window and shows only minor evidence of reaction. The system (soft-landed Pd-4, Pd-6, or Pd-17 dusters on a UNCD Si-coated electrode) shows stable electrochemical potentials over several cycles, and synchrotron studies of the electrodes show no evidence for evolution or dissolution of either the electrode material or the clusters.
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