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The application of gas diffusion electrodes (GDE) modified with carbon black materials at high overpotentials leads to the substantial production of H 2 O 2 via oxygen reduction reaction. The greatest challenge in this process lies in the reduction of the high overpotentials without affecting H 2 O 2 selectivity. One way of circumventing this problem is through the modification of GDEs with coordination compounds. The present work investigates the modification of Printex L6 carbon (CPL6) with different amounts of porphyrin complexes containing the following metallic centers: Mn, Co, Ni, Cu and Zn. The application of 5.0 wt % Co-Porphyrin/CPL6 modifier yielded the best results, with high selectivity for H 2 O 2 generation (90.2%) and marked improvement in catalytic activity (72.6%) compared to CPL6; these positive effects are attributed to the enhancement of both the interaction energy between Co and HOO* reaction intermediate and the effect of the conjugated π-electrons of the CPL6. The application of the modified GDE led to the electrogeneration of 340 mg L−1 of H 2 O 2 with energy consumption of 86.6 kWh kg−1 and 92.1% improvement in efficiency compared to the unmodified GDE. Thus, the findings show that the 5.0 wt % Co-Porphyrin/CPL6 modifier is an excellent cathode for application in H 2 O 2 generation and in electrochemical advanced oxidation processes. [Display omitted] [ABSTRACT FROM AUTHOR]

• PFSA ionomer/N-doped CB is solely used as electrolyte in the PEFC cathode. • Carbon atoms adjacent to nitrogen derive a homogeneous distribution of the ionomer. • Cell performance is notably improved by superior activity and O 2 transportation. • This is attributed to suppression of catalyst poisoning and agglomeration of ionomer. • Cell durability is also enhanced due to higher graphitization of N-doped CB. An implementation of the polymer electrolyte fuel cell (PEFC) electrode, composed of the perfluorinated sulfonic acid (PFSA) ionomer with unprecedented uniform distribution, has recently gained a great attention due to its positive impact on the cell performance as well as durability. However, an issue with the conventional electrodes is a stronger adsorption of sulfonate terminal groups specifically onto Pt catalyst than carbon black (CB) support, that accelerates an inhomogeneous distribution of the PFSA ionomer. In this work, we report a novel PEFC electrode by introducing the ionomer immobilized onto nitrogen-doped carbon black (I/NCB) as electrode binder as well as electrolyte. The carbon atoms adjacent to nitrogen allow a considerable attraction with sulfonated groups over the NCB surfaces, which creates more homogeneous distribution of ionomer when compared with Pt/CB in the conventional electrode. As compared with the conventional electrode, the electrode employing I/NCB presents a superior activity towards oxygen reduction reaction (Pt mass activity increased from 91.3 to 139.6 A g−1) and mass-transport characteristics (mass-transport resistance decreased from 65.9 to 45.5 mΩ cm2), with the cell current density enhanced by 23% at 0.6 V. The enhanced cell durability is confirmed by less degradation in the electrochemically available surface area after the accelerated stress test of carbon support, mainly attributed to the promoted stability of NCB over CB. Given the advances in both performance and durability, the proposed electrode architecture based on I/NCB may provide an alternative pathway in obtaining better electrode kinetics and O 2 transport, along with an exceptional resistivity towards the carbon support degradation. [Display omitted] [ABSTRACT FROM AUTHOR]

A 3D macroporous stainless steel fiber felt (SSFF) is used as base material and a simple water bath method is adopted to directly load Pd nanocatalysts on SSFF to fabricate the air cathode of microbial fuel cells (MFCs). The optimum Pd loading is explored on the basis of the optimized PVP additive amount and reaction temperature. To attain a high ORR activity, a conductive carbon black filling layer is added into the 3D pores of Pd-SSFF. A series of physical and electrochemical tests are conducted to characterize the morphology, chemical composition and oxygen reduction activity and then the obtained cathodes are installed in MFCs for electricity production verification. The results show that the Pd-SSFF cathode at a Pd loading of 0.5 mg cm−2 (Pd-SSFF-0.5) achieves high output voltage and power density (492.65 mV, 390.79 mW m−2) which are comparable to the conventional Pt/C electrode (504.80 mV, 405.47 mW m−2). Furthermore, with Pd-SSFF-0.5 cathode the high-voltage platform duration of MFC in one operation cycle is 2.79 times of that of Pt/C electrode. Excellent mechanical properties (high pressure and corrosion tolerance), high electric energy output and simple fabrication prove it is an efficient strategy to improve the overall performance of MFCs using the obtained cathodes. • 3D macroporous SSFF is proposed as base material in air cathode. • Pd nanocatalysts is loaded directly on SSFF with the simple water bath method. • This loading method can replace the complex preparation process of powder catalysts. • Filling carbon black into the 3D pores of Pd-SSFF helps improving ORR performance. • Excellent mechanical properties and high electric output are achieved by Pd-SSFF cathodes. [ABSTRACT FROM AUTHOR]