155
terminal loss below 50,000 cycles (Fig. 9.1d, open triangles). The preparation of a
highly compact Pt-ML, using the combined processes of H absorption and H
adsorption on Pd to reduce Pt
2+
, leads to the production of a new generation of Pt ML /
Pd/C catalysts with outstanding, unprecedented stability: there was no loss of activity over 200,000 potential cycles (Fig. 9.1d green squares). Furthermore, under
more severe conditions with a potential range of 0.6 V–1.4 V, there were no significant losses of platinum and gold, although the dissolution of palladium was apparent.
The scale-up synthesis method uses a new electrochemical cell that allows a
synthesis of gram quantities of Pt monolayer electrocatalysts per batch. The cell for
a scale-up synthesis has a main body of a Ti container that acts as a working electrode coated with RuO 2 . It is corrosion-resistant and the UPD of Cu is not taking
place on this surface. A Pt black counter electrode (CE) lies in a compartment with
a fritted glass to avoid a contact between CE and nanoparticles. Two-gram batch of
carbon-supported Pd nanoparticles (30 wt-%) was successfully covered by Cu and
then replaced by a Pt monolayer. The average diameter of the Pd nanoparticles is
4.2 nm. The Cu UPD process is carried out until the current acquires a steady value
near zero. After the Cu UPD monolayer formation, a Pt
2+
solution (K 2 PtCl 4 in a
50 mM H 2 SO 4 solution) in a separate reservoir is injected slowly into the cell while
the solution is vigorously stirred to allow Pt atoms to replace Cu monolayers on Pd
surfaces galvanically. The resultant Pt/Pd/C electrocatalyst is washed repeatedly by
filtering. All solutions are purged by Ar gas thoroughly. Cu-mediated layer-by-layer
deposition of Pt monolayer on Pd nanoparticles has been carried out with this cell.
Establishing the scale-up synthesis methodology facilitates preparation of gram
quantities of Pt monolayer electrocatalysts for real fuel cell tests/operations in laboratory. A simple volumetric increase of the cell and other parameters of Pt deposition permits synthesis of 1 kg of catalyst per batch, which is able to bridge
nanoscience of electrocatalysis and fuel cell technology and offer an apparently the
most effective way of minimizing the use of Pt.
Reference
1. K. Sasaki, H. Naohara, Y. Cai, Y.M. Choi, P. Liu, M.B. Vukmirovic, J.X. Wang, R.R. Adzic,
Core-protected platinum monolayer shell high-stability electrocatalysts for fuel-cell cathodes.
Angew. Chem. Int. Ed. 49, 8602–8607 (2010)
Reference
terminal loss below 50,000 cycles (Fig. 9.1d, open triangles). The preparation of a
highly compact Pt-ML, using the combined processes of H absorption and H
adsorption on Pd to reduce Pt
2+
, leads to the production of a new generation of Pt ML /
Pd/C catalysts with outstanding, unprecedented stability: there was no loss of activity over 200,000 potential cycles (Fig. 9.1d green squares). Furthermore, under
more severe conditions with a potential range of 0.6 V–1.4 V, there were no significant losses of platinum and gold, although the dissolution of palladium was apparent.
The scale-up synthesis method uses a new electrochemical cell that allows a
synthesis of gram quantities of Pt monolayer electrocatalysts per batch. The cell for
a scale-up synthesis has a main body of a Ti container that acts as a working electrode coated with RuO 2 . It is corrosion-resistant and the UPD of Cu is not taking
place on this surface. A Pt black counter electrode (CE) lies in a compartment with
a fritted glass to avoid a contact between CE and nanoparticles. Two-gram batch of
carbon-supported Pd nanoparticles (30 wt-%) was successfully covered by Cu and
then replaced by a Pt monolayer. The average diameter of the Pd nanoparticles is
4.2 nm. The Cu UPD process is carried out until the current acquires a steady value
near zero. After the Cu UPD monolayer formation, a Pt
2+
solution (K 2 PtCl 4 in a
50 mM H 2 SO 4 solution) in a separate reservoir is injected slowly into the cell while
the solution is vigorously stirred to allow Pt atoms to replace Cu monolayers on Pd
surfaces galvanically. The resultant Pt/Pd/C electrocatalyst is washed repeatedly by
filtering. All solutions are purged by Ar gas thoroughly. Cu-mediated layer-by-layer
deposition of Pt monolayer on Pd nanoparticles has been carried out with this cell.
Establishing the scale-up synthesis methodology facilitates preparation of gram
quantities of Pt monolayer electrocatalysts for real fuel cell tests/operations in laboratory. A simple volumetric increase of the cell and other parameters of Pt deposition permits synthesis of 1 kg of catalyst per batch, which is able to bridge
nanoscience of electrocatalysis and fuel cell technology and offer an apparently the
most effective way of minimizing the use of Pt.
Reference
1. K. Sasaki, H. Naohara, Y. Cai, Y.M. Choi, P. Liu, M.B. Vukmirovic, J.X. Wang, R.R. Adzic,
Core-protected platinum monolayer shell high-stability electrocatalysts for fuel-cell cathodes.
Angew. Chem. Int. Ed. 49, 8602–8607 (2010)
Reference