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Microbial fabrication is eco-friendly for nobel-metal catalysts typically used in proton exchange membrane fuel cell (PEMFC). In our study, nano-Pd electrocatalysts were successfully prepared by using three Shewanellas as precursors through hydrogen reduction (200 °C) and carbonization (800 °C). The analysis revealed that the catalysts showed outstanding ORR electrocatalytic performance via a predominant four-electron oxygen reduction pathway in alkaline medium. The best performance was obtained for Pd/HNC-32, which showed a mass activity at 0.526 A mg−1, 3.78 times higher than that of commercial Pd/C. Shewanella putrefaciens CN-32 was a more effective Pd-adsorbent. The enhanced performance can be ascribed to the small Pd-particle size and uniform dispersion on microbial support, which results from stronger hydrophilicity of Shewanella putrefaciens CN-32. The content of nitrogen is another key to the performance of Pd/HNC-32. This study developed a promising strategy for screening microbial strains for electrocatalyst fabrication.

A novel oxygen reduction reaction (ORR) electrocatalyst silver@platinum-cobalt-rGO nanoflower (Ag@PtCo-rGO NFs) is prepared by hydrothermal reduction method. The formation of silver chloride likes elm leaf microstructure in the reaction process, performing as a template. The Ag@PtCo-rGO NFs exhibit excellent electrocatalytic activity, whose specific activity is 9 times higher than that of commercial Pt/C. More importantly, Ag@PtCo-rGO NFs demonstrate excellent durability than JM Pt/C for ORR in acid media, as evidenced by accelerated durability test after 40,000 cycles. These excellent performances can be attributed to the special structure, atomic steps and synergistic effect between Pt, Ag and Co. The density functional theory calculation shows that Ag@PtCo has the best activity, which is related to the transition state for O–O bond. This work proposes a promising pathway for the synthesis of surfactant-free nanoflowers structure catalysts with high catalytic performance and low cost.

Shape-tunable PtAg nanocatalysts including PtAg nanoflowers (NFs) and PtAg nanowires (NWs) are prepared by a facile hydrothermal reduction method, via adjusting the precursor ratio of Pt/Ag and subsequent UV-irradiation. Physicochemical characterizations reveal that the as-prepared catalysts have a porous structure, which forms from the conversion of AgCl to Ag nanoparticles. These features favor both oxygen mass transfer and accessibility of active sites. The as-prepared Pt1Ag4 NWs exhibit superior catalytic performances for ORR. The mass activity of Pt1Ag4 NWs is 11.4 times higher than that of 20% Pt/C. More important, the electrochemically active surface area (ECSA) of Pt1Ag4 NWs is 2.5 times larger than that of commercial Pt/C.

There are many types of cathodic oxygen reduction catalysts for proton exchange membrane fuel cell (PEMFC). Among them, Pt-based catalysts are most likely to be industrialized because of their incomparable high activity. However, most of the Pt-based catalysts have not reached the maximum activity and stability. Herein, porous carbon nanofibers (p-CNF) with self-nitrogen-doped as catalyst supports were successfully prepared by the method of electrospinning. After functionalization, the functionalized porous carbon nanofibers (f-p-CNF) were loaded with PtPd alloy nanoparticles to obtain the catalyst (Pt0.66Pd0.33/f-p-CNF), which has excellent electrochemical performance. Its specific activities (SA) and Pt mass activities (Pt MA) are 1.73 and 1.86 times of the commercial JM 20% Pt/C (JM20), respectively. The results can be attributed to the porous structure of nanofibers, which not only facilitate the transmission of gas-liquid and electron but also increase the exposure of active sites. And the doped nitrogen of fibers may regulate the electronic structure of the metal active substance to increase the activity. This work provides catalyst with novel structure which could enable PEMFCs to be more efficient in operation.

One-dimensional carbon nanofibers hold great promise to be potential candidates as high-efficiency electrocatalysts for oxygen reduction reaction (ORR). However, the catalysts in powder form always aggregate when preparing catalyst layer, which significantly hinders the extensive application. Herein, we report the facile synthesis of iron and nitrogen co-containing porous carbon nanofibers derived from PAN nanofibers existing as a flexible film via the electrospinning method, which could avoid aggregation when fabricating catalyst layer of fuel cells. The Fe–N/N–C NFs exhibit onset potential of 0.95 V and the half-wave potential of 0.78 V in 0.1 M KOH solution, suggesting superior electro-catalytic activity for ORR. Meantime, for Fe–N/N–C NFs catalyst, it shows a nearly four electron transferring process and the current density only decreases by 14.2% after 40,000 s. This easy and facile method provides a new idea for synthesis of oxygen reduction reaction with high-activity and good-stability.

While noble metals loaded on carbon-based supports are commonly used as oxygen reduction catalysts for fuel cell cathodes, the preparation process is complicated and expensive cost. In this paper, Pd2+ was first adsorbed on Shewanella by its adsorption characteristics, then the Pd supported on Shewanella catalyst was obtained after carbonization at 600 °C and hydrogen reduction at 200 °C. The Shewanella cells retain the rod shape of bacteria following pyrolysis under high temperatures, while N and Pd heteroatoms are uniform distribution on the carbon matrix. As a result, Pd supported on Shewanella catalyst exhibits excellent electrocatalytic activity for ORR via a dominant four-electron oxygen reduction pathway in alkaline medium. More importantly, the mass activity of the prepared catalyst was 5.8 times higher than that of commercial Pd/C, and its stability was also better than the Pd/C, which could be promising alternatives to costly Pt-based electrocatalysts for ORR.

A novel platinum-palladium/carbon nanowires (PtPd/CNWs) catalysts are successfully prepared by electrospinning for the oxygen reduction reaction (ORR). The prepared PtPd/CNWs catalysts exist in the form of membrane, which can be directly applied as catalyst layer in membrane electrode assembly. The ORR activity of binary PtPd/CNWs catalysts are enhanced significantly in comparison to the ternary platinum-palladium-gold/carbon nanowires (PtPdAu/CNWs) catalysts and 20% Pt/C. Here, the gold in PtPdAu/CNWs mainly exists in larger gold nanoparticles rather than in the form of ternary alloy with Pt, Pd. The mass activity and special activity of PtPd/CNWs are 4.230 times and 4.225 times than that of 20% Pt/C, respectively. Moreover, the electrochemical active surface areas (ECSAs) of PtPd/CNWs catalysts almost keep constant after 5000 potential cycling, whereas 20% Pt/C drops almost 40% after 5000 potential cycling.

Here we report a dramatically enhanced hydrogen evolution reaction (HER) catalyst by acid etched MoS2 (A-MoS2). For the etching and oxidation effects of HNO3, the active site and electrical transport are significantly improved by simply controlling of processing time. The A-MoS2 exhibits promising electrocatalytic performance, including much smaller onset overpotential (∼80 mV), an overpotential of 210 mV at 10 mA/cm2, and a Tafel slope of 97 mV/dec (the pristine MoS2 180 mV/dec). The enhanced HER performance of MoS2 may be attributed to the increased edge S atoms and the charge induced by the O doping.

To enhance the activity and durability of platinum (Pt) or platinum-based catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs), fabrication of low-cost platinum catalysts with durable structure is necessary. Here, a series of one-dimensional (1D) platinum-gold/titanium dioxide nanowires (PtAu/TiO2 NWs) catalysts with different Pt/Au/Ti ratios were synthesized by electrospinning, and the microstructure as well as its electrochemical properties for ORR were investigated. The results illustrate that PtAu/TiO2 NWs indicate a parabolic-type ORR performance as a function of compositions. The optimized Pt1Au1/(TiO2)1 NWs exhibited 4.19 times in mass activity and 2.82 times in SA when compared with commercial Pt on carbon catalyst (20% Pt/C). In addition, the stability test shows that the ECSA of Pt1Au1/(TiO2)1 NWs present almost 20% decrease, while the 20%Pt/C drops more than 40% at the same condition. The extraordinary activity of Pt1Au1/(TiO2)1 NWs could be attributed to the synergistic effect of TiO2 and the durability attributed to Au and C skin. The nanowires with larger specific area show that the Pt electronic structure can be changed by the neighbouring TiO2, further decreasing the d-band gap to enhance catalytic activity.

As catalytic active sites of nitrogen (N)-doped carbon nanomaterials (CNMs) for oxygen reduction reaction (ORR) are always under debate, synthesis of high purity pyridinic-N dominated CNMs is an effective approach to study the relation between pyridinic-N and active sites, as well as catalytic mechanism for ORR. Herein, the carbon nanofibers (CNFs) etched by hydrofluoric (HF) acid can be used to synthesize pure pyridinic-N, suggesting that the exposed edge-patterned surface facilitates to synthesize pure pyridinic-N. Moreover, it reveals that the carbon atoms adjacent to pyridinic-N could be the catalytic active sites for ORR.

The Fe-N-C nanofibers (NFs) exhibit excellent electro-catalytic activity for oxygen reduction reaction (ORR), which is essential for energy conversion system. Compared with the traditional ink-based electrode, we synthesized the structured Fe-N-C ANFs/CP (activated NFs derived from polypyrrole(PPy) doped with iron atoms in situ grown on carbon paper) by electrochemical polymerization. Herein, we investigate the effect of the iron concentration on the electro-catalytic activity for ORR, revealing that the as-prepared 0.05-Fe-N-C ANFs exhibit superior electro-catalytic activity than 0.01-Fe-N-C ANFs, 0.03-Fe-N-C ANFs as well as 0.10-Fe-N-C ANFs and excellent durability in alkaline solution. It is shown that the better electro-catalytic activity of 0.05-Fe-N-C ANFs for ORR could be ascribing to the fluffy fibrous structure, higher Fe-N x concentration, and well-dispersed catalytic active sites.

The controllable synthesis of single nitrogen (N) type doped carbon nanomaterials (CNMs) is of significant importance to evaluate the effects of different N types on electro-catalytic activity for oxygen reduction reaction (ORR) in experiment. Herein, the chaotic edge planes of the as-synthesized platelet carbon nanofibers (plCNFs) are tailored by acid etching of HF to obtain abundant exposed active edge sites while maintaining the interior graphene patterns intact. The N bonding configuration belonging to pyridinic type is nearly 100% and the concentration of the pyridinic-N in the tailored plCNFs reaches up to 12.61 at.%. Electrochemical tests show that N-plCNFs (HF) exhibits improved ORR activities compared with N-plCNFs and the carbon atoms adjacent to pyridinic-N could be the catalytic active sites for ORR. In addition, the generation mechanism of pyridinic-N in tailored plCNFs is briefly elaborated.

The structured electrode has the advantages of polymer binder-free, non-precious-metal and without multiple and tedious manual assembly, exhibiting superior electro-catalytic activity for oxygen reduction reactions (ORR), compared with the traditional ink-based electrode. The structured CP/Fe-N-CNFs (Fe and N containing carbon nanofibers (CNFs) in-situ grown on carbon paper (CP)), has been one-step synthesized by chemical vapor deposition (CVD). In this paper, it can be concluded that the structured CP/Fe-N-CNFs with 0.30 at.% Fe-N x moieties exerts the most positive onset-potential (−0.05 V), peak potential, and largest peak current density. The measured current density of the structured Fe-N-CNFs at −0.8 V is increased by 56.3% compared to that of the traditional Fe-N-CNFs. The traditional Fe-N-CNFs exhibit stronger alkaline tolerance comparing with commercial Pt electrode. That is, the pronounced catalytic activity of the structured Fe-N-CNFs might attribute to the homogeneous and undiluted active sites compared to that of the traditional Fe-N-CNFs.

Pt-Au nanoparticles supported on carbon black (PtAu/CBx) are produced by a facile chemical reduction method and subsequent heat treatment. In this paper, the effects of heat treatment temperature on structure and electrochemical properties are investigated. A series of catalysts, including PtAu/CB, PtAu/CB400 and PtAu/CB600, with different particle size are synthesized. The particle size of PtAu/CB600 is slightly larger than that of PtAu/CB400 and PtAu/CB, but the electrochemical performance of PtAu/CB600 is the best due to more active sites available in PtAu/CB600. Moreover, the durability of PtAu/CB600 and commercial Pt/C is researched in acidic media. After 5000 cycles accelerated durability test, it can be seen from CV and LSV that PtAu/CB600 shows better stability. Therefore, the better activity and stability of PtAu/CB600 can be ascribed to the ordered structure and the synergistic effect of Pt and Au.

Novel (B,N)-doped three-dimensional (3D) porous graphene–carbon nanotubes (CNTs) can be used as an excellent alkaline and acid tolerant electrocatalyst for both the oxygen reduction reaction (ORR) and the hydrogen evolution reaction (HER). Based on density functional theory, the H and O atoms’ pre-and post-adsorption energy can effectively reduce the reaction energy barrier.