Direct liquid fuel cells (DLFCs) have been received much attention due to its safety, transportation, storage and utilization. Among them, the formate (HCOO
-) as a fuel have more attracted due to its faster oxidation kinetics compared with formic acid (HCOOH) in optimal pH and higher theoretical voltage compared with the methanol and the ethanol.[1-3] Furthermore, the HCOO
- has being predominant form in alkaline media and there has been no poisoning effect on palladium (Pd) catalyst on the oxidation of HCOO
- such as carbon monoxide which is the inevitable species as the oxidation of formic acid and HCOO
- on platinum (Pt). In the point of view of mechanistic study, decreasing the chemisorption strength of the adsorbed hydrogen (H
ads) plays a key role in determining the enhanced catalytic activity of the oxidation of HCOO
- on Pd, since the desorption of H
ads is rate-determining step (RDS) of the oxidation of HCOO
- on Pd so that it blocks an active site of the adsorption of HCOO
‑.[4] By alloying Pd and other transition metal such as copper (Cu) or gold (Au), the adsorption strength on Pd has been weakened through the d-band of Pd has been more filled due to the electron transfer from other transition metal to Pd.[5] In addition, the adsorption strength on Pd can be also weakened by the electronic effect that the d-band of Pd is more filled by electrons of heteroatoms such as hydrogen (H) and boron (B) entered to Pd lattice.[4,6]
In previous study [4], we had synthesized Pd-H catalyst on the carbon powder via sodium borohydride as a reducing agent and observed enhanced catalytic activity of the oxidation of HCOO- despite of the large particle size compared with that of commercial Pd/C. Because the morphology is also deeply related to the catalytic activity, we have investigated the correlation between structural changes such as dispersity or particle size and catalytic activity of the oxidation of HCOO- by controlling synthesizing temperature. In this study, we have synthesized Pd-H catalyst using a characteristic of lattice on the carbon powder of in accordance with temperatures and comparing their surface, particle size, crystal structure and catalytic activity of the oxidation of HCOO- using electrochemical method and physicochemical analysis.
Refrerences
- J. Joo et al., ACS catalysis, 2015, 5, 6848.
- S. Uhm et al., Angewandte Chemie, 2008, 120, 10317.
- S. Uhm et al., Physical Chemistry Chemical Physics, 2009, 11, 9326.
- M. Choun et al., Catalysis Today, 2017, 295, 26.
- O. Yepez et al., International Journal of Hydrogen Energy, 2002, 27, 99.
- C.W.A. Chan et al., Nature Communication, 2014, 5, 5787.
