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The properties of the anode material and structure are critical to the microbial growth and interfacial electron transfer between the biofilm and the anode. In this paper, we prepared the nitrogen-doped 3D expanded graphite foam (NEGF) by simple, rapid and inexpensive methods of liquid nitrogen expansion and hydrothermal treatment from commercial graphite foil (GF). X-ray photoelectron spectroscopy confirmed the success of nitrogen doping on expanded graphite foam (EGF). Using cyclic voltammetry and electrochemical impedance spectroscopy, the NEGF and EGF electrode exhibited increased electrochemical active surface area and fast interfacial electron transfer ability than that of pristine GF, and NEGF electrode performed even better. Scanning electron microscopy revealed that NEGF and EGF possessed graphene-like structure and large surface area. MFCs equipped with NEGF or EGF anodes, respectively, achieved maximum power density of 0.739 and 0.536 W m -2 , which was about 17.4 and 12.6 times larger than that of MFCs with GF anodes (0.0451 W m -2 ). The anode and cathode polarization curves further confirmed that the different anode other than the cathode was responsible for the advanced performance of MFCs. The morphology of the biofilm on three kinds of anodes proved the densest biofilm formed on NEGF anode. All the results indicated the synergistic effect of 3D graphene-like structure and N-doped surface on the performance of MFCs, which might provide special insights into designing simple and efficient route for anode construction to achieve promising electricity generation.

Novel Co-N-S/C catalysts supported on carbon were obtained using a two-step procedure. The procedure consisted of the synthesis of a carbon-supported Co-2-mercaptobenzothiazole (denoted as Co-MBT/C) complex using a solvent-milling method and the pyrolysis of the Co-MBT/C complex. 2-Mercaptobenzothiazole (MBT) was used as the nitrogen and sulfur ligand for Co-MBT complex formation. X-ray diffraction (XRD), TEM, EDS and elemental mappings were used to characterize the structure changes in these catalysts before and after the heat-treatment. Several catalysts were synthesized by varying the amount of cobalt salt and pyrolysis temperature. The results showed that the optimal cobalt salt content and pyrolysis temperature were around 25 wt% and 800°C. Under the optimal conditions, an onset potential of 0.20 V and a half-wave potential of 0.05 V were reached in an alkaline electrolyte, and the Co-N-S/C catalyst possessed high catalytic activity and catalytic stability towards an oxygen reduction reaction (ORR). These results indicated that Co-N-S/C is a promising catalyst for the ORR.

The development of highly efficient and stable non‐noble bifunctional catalysts for overall water electrolysis has attracted considerable attention in recent decades. Owing to appealing chemical and structural properties, two‐dimensional (2D) porous nanocomposites have been considered as the first‐class candidates for water electrolysis. Herein, an effective 2D bifunctional catalyst, CoO‐modified nitrogen and sulfur co‐doped ultrathin porous carbon nanoplates, has been synthesized by pyrolysis of ultrathin [CoII(Tdc)(4,4′‐Bpy)]n (Tdc=thiophene‐2,5‐dicarboxylate; Bpy=4,4′‐bipyridine) nanoplates at 600 °C under a nitrogen atmosphere (denoted CoO/N‐S‐UPCNPs‐600). CoO/N‐S‐UPCNPs‐600 possesses favorable properties for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), such as a thinner thickness in ultrathin porous carbon nanoplates (UPCNPs), more defects, and a larger specific surface area. As a result, CoO/N‐S‐UPCNPs‐600 exhibits high catalytic activity and stability towards both OER and HER in alkaline medium. Its overpotentials and Tafel slopes are as low as 240 and 110 mV at 10 mA cm−2 and as small as 62 and 94 mV dec−1 for OER and HER, respectively. Furthermore, an alkaline water electrolyzer fabricated with CoO/N‐S‐UPCNPs‐600 as both anodic and cathodic catalysts delivers an attractive cell potential of 1.63 V at 10 mA cm−2 and shows no obvious degradation over 20 h. Therefore, the resultant 2D ultrathin porous nanocomposite is expected to be applied for efficient water electrolysis. [ABSTRACT FROM AUTHOR]

Nowadays, the exploration of highly active and cost-effective bifunctional catalysts for oxygen electrode reactions is crucial for various energy conversion applications. Herein, to obtain a highly effective Co-N/C non-precious metal bifunctional catalyst, 3,5-diamino-1,2,4-triazole (Hdatrz) was used for the first time as a Nitrogen precursor. Different Co-Hdatrz complex weight percentages and thermal treatment temperatures had resulted in varying catalyst performance. Among the resulting catalysts, due to the highest active N content, the smallest charge transfer resistance and the synergy of CoO with carbon black, the Co-N 30% /C-600 catalyst (the Co-Hdatrz complex weight percentage was 30% and the thermal treatment temperature was 600 °C) demonstrated the highest catalytic activity towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline medium, which was superior to Pt/C. Additionally, the Co-N 30% /C-600 catalyst also showed excellent methanol tolerance and ORR and OER stabilities compared to Pt/C. Thus, the Co-N 30% /C-600 catalyst may serve as a promising bifunctional electrocatalyst in fuel cells, metal-air batteries and water splitting cells. [ABSTRACT FROM AUTHOR]

Nowadays, the design and development of highly efficient and low–cost bifunctional electrodes for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are in urgent demand for energy conversion and storage technologies, such as fuel cells, metal–air batteries and water–splitting cells. Herein, to mitigate this challenge, a novel cost–effective flower–like Ni and N codoped hierarchical porous carbon microspheres (denoted as F-Ni/N-HPCMs) electrode has been fabricated by a simple two–step method. Benefiting from the unique structure property, the F-Ni/N-HPCMs show excellent ORR and OER performance. More importantly, H 2 –O 2 alkaline polymer electrolyte fuel cell (APEFC) fabricated with the F-Ni/N-HPCMs cathode shows an open circuit potential of 0.84 V and a high performance of 208 mW cm − 2 . And, the performance is better than the reported APEFCs constructed with other non–precious metal electrodes. Hence, this work provides a new strategy to fabricate high performance electrodes for fuel cell storage. [ABSTRACT FROM AUTHOR]

Studies have shown that the performance of electrode materials greatly depends on their structures and compositions. Herein, unique hierarchical peanut-like Co and N codoped porous carbon (Co/N-PC) had been synthesized by using inexpensive melamine, formaldehyde and cobalt acetate as raw materials via a simple template-free hydrothermal reaction followed by heat treatment. The formation process of the peanut-like precursor was discussed in-depth, indicating that the morphological evolution with time followed a pathway of: solid microspheres → wrinkled and ultrathin shells wrapped microspheres → the peanut-like precursor formation. Furthermore, the unique structure combines the advantageous features of high surface area, sufficient active sites, easy access to medium and rapid mass transport. As a result, the peanut-like Co/N-PC showed high catalytic activity, superior methanol crossover resistance and excellent catalytic stability towards oxygen reduction reaction (ORR) in alkaline medium. Notably, the peanut-like Co/N-PC possessed a comparable ORR half-wave potential to commercial 20 wt% Pt/C catalyst. Therefore, it can be expected that the peanut-like Co/N-PC will be a promising alternative to commercial Pt/C catalyst for fuel cells. [ABSTRACT FROM AUTHOR]

The most promising non-precious metal oxygen reduction catalysts are M-Nx/C (M = Fe and/or Co) materials. Moreover, N-containing precursor is one of the important factors that affect oxygen reduction reaction (ORR) activity of M-Nx/C materials. In this paper, we want to study nitrogen precursor effects on ORR activity of Co-Nx/C catalysts by varying N content and N/C ratio of the nitrogen precursor. In this regard, three Co-Nx/C catalysts were synthesized using a solvent-milling method followed by high temperature treatment. The results showed that the increase in N content and N/C ratio did not necessarily cause the improvement of ORR activity of the Co-Nx/C catalyst. The most active catalyst, Co-HQ/C-800 (heat treatment of carbon supported Co-HQ complex at 800 °C for 2 h), was obtained using 8-hydroxyquinoline (8-HQ) as the nitrogen precursor. XPS analysis demonstrated that more graphitic N and Co-Nx active sites were responsible for better ORR activity of the Co-HQ/C-800 catalyst. The electrochemical property of the three Co-Nx/C catalysts was evaluated by linear sweep voltammetry (LSV), chronoamperometric measurements, accelerated durability tests (ADT) and H 2 /O 2 alkaline fuel cell (AFC) tests. [ABSTRACT FROM AUTHOR]