Improvement Of CO Tolerance Research Articles

Low-Pt anodes with gradient molybdenum isomorphism for high performance and anti-CO poisoning PEMFCs

The development of low Pt-loading hydrogen oxidation reaction electrocatalysts with high catalytic activity, durability, and resistance to CO poisoning is essential for the commercialization of proton exchange membrane fuel cells. Herein, two hybrid catalysts coupled with single atoms are prepared. Electrochemical tests show that PtMo1/KB (Ketjen Black) (1.85 wt% Pt) exhibits extraordinary HOR activity and durability, with the mass activity in electrochemical cells and even PEMFCs are 8.36 and 2.71 times higher than that of commercial Pt/C, respectively. In addition, PtMo10/KB with novel configuration performed super high CO resistance (1000 ppm) in both three electrode and PEMFC measurement with an ultra-low Pt loading of 1.56 wt%, demonstrating the high application value in the next generation highly efficient PEMFC. DFT calculations also show that the adsorption energy of the intermediates H* and CO is optimized by tuning the d-band center of Pt, thus enhancing the HOR activity and CO tolerance of the catalyst. Meanwhile, in situ CO-adsorption surface-enhanced infrared adsorption spectroscopy also confirms that the weakening of the Pt-CO bond strength and the adsorption energy of CO contributes to the improvement of CO tolerance in PtMo10/KB.

Ni(OH)2 Decorated Pt-Cu Octahedra for Ethanol Electrooxidation Reaction.

Here we report the synthesis of 9 nm Ni(OH)2 decorated Pt-Cu octahedra (Ni(OH)2-PtCu) in one-pot synthesis for ethanol oxidation reaction (EOR) electrocatalysis in acidic electrolyte. To prepare Ni(OH)2-PtCu octahedra, CO gas was directly introduced in a reaction process as selective capping agents on the PtCu(111) facet. Ni(OH)2 was naturally deposited on the Pt-Cu octahedra during the synthesis. Carbon supported Ni(OH)2-PtCu (Ni(OH)2-PtCu/C) as an EOR catalyst showed enhanced CO tolerance due to the existence of oxophilic Ni(OH)2 on the surface of Pt-Cu, facilitating water dissolution to produce OH adsorption and to promote complete CO oxidation to CO2. In addition, Pt-Cu alloy composition also showed improvement of CO tolerance because of modified d-band structure of the Pt atoms, thereby weakening the binding strength of CO on the catalysts. Therefore, the Ni(OH)2-PtCu/C showed enhanced EOR activity and durability compared to the Pt-Cu octahedra and commercial Pt/C counterparts.

Suppression of CO Adsorption on PtRu/C and Pt/C with RuO2 Nanosheets

RuO2 nanosheets were studied as a promotor for the hydrogen oxidation reaction in the presence of 300 ppm CO/H2. The hydrogen oxidation current in 300 ppm CO/H2 for RuO2 nanosheet modified PtRu/C catalyst (RuO2:Pt:Ru = 0.5:1:1 (molar ratio)) exhibited higher CO tolerance than Pt1Ru1/C and Pt2Ru3/C. Based on hydrodynamic voltammetry, chronoamperometry and CO stripping voltammetry, the addition of RuO2 nanosheets is suggested to suppress CO adsorption on the catalyst surface, resulting in an improvement in CO tolerance. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. [DOI: 10.1149/2.0011505eel] All rights reserved.

Design of Pt-CeOx hetero-interface on electrodes in polymer electrolyte membrane fuel cells

Pt-CeOx interface on Pt electrodes was prepared for improvement of both oxygen reduction reaction (ORR) activity of Pt cathode and CO tolerance of Pt anode. The surface of Pt-CeOx nano-particle/C electrode mainly consists of metallic Pt, ionized Pt (i.e. Pt2+) and Ce3+ species. The ORR activity on Pt was improved by the formation of Pt-CeOx interface. In-situ XAFS analysis suggests that cerium oxide surface in the Pt-CeOx/C was oxidized instead of Pt surface by electrochemical redox reaction of CeOx at room temperature. This suggests that the Pt-CeOx interface plays key role for improvement of cathode performance. Also, CO tolerance of Pt was improved by the formation of aforementioned interface. The improvement of CO tolerance of Pt was also observed by using in-situ IR analysis. Based on all experimental data, it is concluded that the design of defect structure in Pt-CeOx provides us opportunity to make the breakthrough electrodes for fuel cell application.

Effects of Pt Shell Thicknesses on the Atomic Structure of Ru–Pt Core–Shell Nanoparticles for Methanol Electrooxidation Applications

In this research, core-shell electrocatalysts comprising a Ru core covered with precisely controlled 1.5-3.6 atomic layers (ALs)-thick Pt atoms are synthesized. The sample with 1.5 ALs shows a 3.2-fold improvement in CO-tolerance and 2.4-fold current enhancement at the conventional battery operation potential (I(300), at 300 mV vs Ag/AgCl) during methanol oxidation as compared with conventional all-Pt nanoparticles. The origin of the enhanced performance and the atomic structure of the core-shell nanoparticles are elucidated to be mainly dominated by the lattice strain (possibly some slight effect of heteroatomic interactions) then by the combination of ligand effects and bifunctional mechanisms when the shell crystal is thicker than 2.7 ALs.

Improvement of CO Tolerance of Proton Exchange Membrane Fuel Cell by an Air-Bleeding Technique

This study investigates the improvement of proton exchange membrane fuel cell (PEMFC) carbon monoxide by periodic air dosing. The carbon monoxide in the fuel gas leads to a significant loss in power density due to CO poisoning in the anode. The method involves bleeding air into the anode fuel stream (H2–CO), which contains CO in various concentrations (20ppm, 52.7ppm, and 100ppm). In the transient CO poisoning test, air bleeding is performed for four different periodic air dosing and cell voltage is fixed at 0.6V. The result of a dosing of air for 10s in intervals of 10s is similar to that of continuous air bleeding except for 100ppm CO. The CO tolerance of the fuel cell and cell performance recovery from poisoning can be improved by air bleeding.

Improvement of CO tolerance of proton exchange membrane (PEM) fuel cells by a pulsing technique

Proton exchange membrane (PEM) fuel cells are currently being developed as alternative energy conversion systems for vehicular as well as for stationary power applications. The supply of hydrogen obtained by the reforming of alcohols or hydrocarbons to PEM fuel cells requires an extensive gas clean-up, as contaminants such as CO are poisonous to the employed catalysts. A new method of operating PEM fuel cells with reformed hydrogen with reduced requirements for gas cleaning is presented. The pulse technique allows the direct feeding of reformate gas into the fuel cell without a significant loss of performance. The electrical pulses increase the anode potential to values at which the CO is oxidised to CO2. In this way the catalyst surface is continuously cleaned and the loss of cell voltage is minimised. The optimised operating parameters for the pulses (namely pulse amplitude, duration and frequency) were investigated and determined as a function of CO content in the feed gas. It was found that the optimised pulse duration is not changed significantly for the different CO contents investigated (100, 1000 and 10000 ppm). In contrast, the pulse frequency needs to be adjusted to obtain CO tolerance at different CO concentrations in the hydrogen gas. This operating method greatly increases the design options of fuel cell systems for different applications.