title: Size-Dependent Activity of Palladium Nanoparticles: Efficient Conversion of CO2into Formate at Low Overpotentials.
abstract: Remarkable size-dependent activity of palladium nanoparticles (PdNPs) towards formate production is evident at very low overpotentials (-0.1 to -0.5 V vs. RHE). Size-selective PdNPs, chemically synthesized at sizes of 3.8-10.7 nm, effected an electrochemical CO2reduction reaction in aqueous 0.5 m NaHCO3. The faradaic efficiency of formate production (FEformate) on 3.8 nm PdNPs exceeded 86 % at E=-0.1 V versus RHE, whereas on 6.5 nm PdNPs an even higher FEformateof 98 % was observed. However, FEformatedecreased for larger PdNPs. The superior efficiency towards formate production at low overpotentials is rationalized in terms of a changed catalytic pathway through PdH phases. The observed maximum in the formate efficiency for a mean particle size of about 6.5 nm is discussed in terms of counterbalancing the size-dependent effects of a competing CO2reduction reaction and a parasitic hydrogen evolution reaction. Production rates of formate are also remarkably high at -0.3 V versus RHE with 539.9 and 452.3 ppm h-1mgPd-1for the 6.5 and 3.8 nm PdNPs, respectively.
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012, Bern, Switzerland.
authors.forename: Motiar
authors.initials: M
authors.lastname: Rahaman
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012, Bern, Switzerland.
authors.forename: Abhijit
authors.initials: A
authors.lastname: Dutta
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012, Bern, Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Broekmann
mesh_terms: D002245:Carbon Dioxide / Q000737:chemistry*; D055664:Electrochemical Techniques; D005561:Formates / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D010165:Palladium / Q000737:chemistry*
chemical_list: D005561:Formates; C030544:formic acid; D002245:Carbon Dioxide; D010165:Palladium
keywords: electrochemistry; formate; nanoparticles; palladium; size effect