| Polymer electrolyte membrane fuel cells (PEMFCs) are regarded as ideal candidates for stationary and mobile power generation due to their high energy conversion efficiency and low environmental impacts. However, the poor durability, high cost and low Pt utilization of electocatalyst have been recently recognized as the most important issues to be addressed before the commercialization of PEMFCs. At present, carbon-supported Pt nanoparticles (NPs) in the particle diameter range of ca. 2-6 nm are still the most widely used cathode catalysts in PEMFCs. The poor durability of the Pt/C catalyst is reflected by a fast and significant loss of platinum electrochemical surface area (ECSA) due to carbon support corrosion and Pt aggregation/ dissolution/ Oswald ripening. In addition, the conventional catalyst layer of PEMFCs is usually obtained by coating a random paste mixture of Pt/C powders, Nafion polymer electrolyte and solvents on a gas diffusion layer. Therefore, only part of the Pt NPs can be utilized by PEMFC electrode reactions that have continuous electronic channels to current collector and continuous proton channels to electrolyte polymer. So, it is necessary to change the conventional catalyst structure of PEMFCs. Based upon the above problems, a series of high performance catalysts with high durability and Pt utilization are prepared form the aspects of catalyst modified, support and PEMFC catalyst structure for enhanced utilization of noble metal Pt.Firstly, we report a novel strategy to enhance Pt NPs durability and activity in Pt/C catalyst by using conducting polyaniline to selectively decorate carbon support of Pt/C catalyst. The stability and activity of PANI@Pt/C catalyst were evaluated by using accelerated durability test (ADT), LSV, TEM and XPS. The prepared PANI@Pt/C catalyst exhibits a Pt mass and specific activity nearly 1.6 and 1.8 times higher than the commercial Pt/C catalysts. The accelerated stability test shows that the PANI@Pt/C catalyst only decreased～30% in electrochemical surface area (ECSA), whereas the Pt/C catalysts have lost～83% of their initial ECSA. We ascribe the high activity and stability of the PANI@Pt/C catalyst to its special PANI-decorated core-shell structure, which can enhance the Pt-support interaction and help to inhibit Pt dissolution/ re-deposition, aggregation and ripening, provide corrosion resistance to the carbon support.Second, we present a novel thiolated CNTs (SH-CNTs) support by directly linking thiol groups on the CNTs surface. The Pt/SH-CNTs catalyst was synthesized by high-pressure colloidal method. The stability and activity of Pt/SH-CNTs catalyst were evaluated by using ADT, LSV, TEM and XPS. The TEM and CV results show that the SH-CNTs have abundant–SH groups on their surface, which serve as anchor centers for achieving high Pt dispersion and ensure the high activity of the catalyst. The ADT tests show that the Pt ECSA of Pt/SH-CNTs catalyst only decreased approximately 22.3% after 1,500 CV cycles, whereas the Pt/pristine-CNTs and Pt/COOH-CNTs catalysts lost about 48.1% and 81.3% of their initial ECSA, demonstrating that the Pt/SH-CNTs catalyst was more electrochemically stable than the Pt/pristine-CNTs and Pt/COOH-CNTs catalyst. The improved durability of the catalyst was attributed to the strong S-Pt interaction, which can alter the Pt electronic structure and helps to inhibit Pt dissolution, ripening and aggregation.Thirdly, we report a novel method based on alternative ion-exchange electrodeposition (AIEE) for constructing high Pt utilization PEMFC electrodes. The prepared AIEE electrode was assessed by CV, SEM and single cell test. CV and SEM test showed that the Pt particle size, shape and distribution can be controlled by modulating the Nafion content and AIEE times. The power output of the MEA with a 0.014 mg Pt cm-2 AIEE electrode is approximately 2.2 times larger than the one with a conventional Nafion-bonded electrode. The excellent performance of the MEA with the AIEE Pt electrodes, anode or cathode, can be ascribed to its high Pt utilization.Finally, we present a novel bifunctional catalyst support by directly linking -SO3H groups on the CNTs surface. The Pt/SO3H-CNTs catalyst was synthesized by high-pressure colloidal method. The stability and activity of Pt/SO3H-CNTs catalyst were evaluated by using ADT and single cell test. The ADT tests show that the Pt ECSA of Pt/SO3H-CNTs catalyst only decreased approximately 33% after 1,500 CV cycles, whereas the commercial Pt/C lost about 88% of their initial ECSA, demonstrating that the Pt/SO3H-CNTs catalyst was more electrochemically stable than the commercial Pt/C catalyst. The single cell test show that the maximum power output of the MEA prepared with Pt/SO3H-CNTs cathode (0.3 mg cm-2) and Nafion-bonded Pt/C anode (0.1 mg cm-2) is 0.9 W cm-2, which is higher than the MEA with Nafion-bonded Pt/C anode (0.3mg cm-2) and Nafion-bonded Pt/C cathode (0.1 mg cm-2). This result indicates that Pt/SO3H-CNTs hold a high Pt utilization than a conventional Pt/C catalyst.
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