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In this work, we initially report a detailed advancement in the utilization of metal-N4 chelate macrocycles in the oxygen reduction reaction (ORR). Then, iron(II) phthalocyanines supported on two different carbon-based supports specifically carbon nanotube and black pearl (carbon spheres) were synthesized and their activities toward ORR in alkaline media were studied. With the help of physical and surface characterization like Raman, BET, XRD, XPS, and electron microscopy analysis, the similarity in surface chemistry and surface area of the materials and the differences in the structure and morphology of the supports were established. This work also brings forth the effect of support properties on the electrocatalytic activity of the materials by a detailed electrochemical analysis using rotating disk electrode in oxygen saturated 0.1 M KOH. Comparison with existing literature on Fe-phthalocyanine supported on diverse carbon support is presented.

Platinum group metal-free (PGM-free) catalysts are the most promising materials for substituting expensive platinum catalyst for efficient oxygen reduction reaction (ORR), particularly for microbial fuel cells. For these devices contamination due to wastewater is one of the major issues due to the presence of various poisoning anions. The known nitrite contamination effect over PGM-free was studied through rotating disk electrode (RDE) technique in neutral media to understand its patterns. The results were then compared to other contaminants commonly found in wastewater such as chloride (Cl-), perchlorate (ClO4-), and nitrate (NO3-) in the concentration range of 0.05-50 mM. Onset potential (Eonset), half wave potential (E1/2), limiting disk current density (Jlim) and Tafel slopes variations were the parameters exploited to identify specific or unspecific adsorbed contaminants. Chloride and nitrate had no negative effect on ORR performance, while perchlorate slightly reduced the catalyst function with no permanent issues. Durability tests (1000 cycles) were also performed to ensure the stability of the catalyst for relatively long time.

Highly water-dispersible, redox-active 1D coordination polymers (CPs) have been synthesized using low-cost precursors. These CPs, containing chloranilic acid as organic ligand and a transition element, such as Fe and Mn as a metal center, form long-term stable slurries containing up to 100 g/L solid particles in aqueous media (0.5 M NaCl, 1 mg carbon nanotubes). Voltammetry studies showed that the iron-based particulate slurries exhibited three different redox stages with no metal plating. However, the suspensions with manganese-based coordination polymers experienced a metal plating process in the same potential window range as for the iron-based CPs. Moreover, the particulate suspension of iron-CPs shown longer-term stability than their isostructural analogs based on manganese. The 1D Fe-CPs were used as catholyte and anolyte in a symmetrical cell with a low-cost size exclusion cellulose membrane acting as a separator. The cell experienced a reversible capacity value of 45 mAh/g (225 mAh/L) at a current density value of 20 mA/g for 50 cycles (~12 days) at neutral pH. This study opens the possibility of using inexpensive coordination polymers as single bifunctional electrolyte material in aqueous batteries and other sustainable energy storage-related systems.

The lithium ion storage properties of a series of metal-organic frameworks (MOFs) with formula {[M(L)(HO)]HO}n and [M(CA)(Pyz)]n (where L refers to the tetraoxolene ligands: CA = chloranilate and DHBQ = dihydroxybenzoquinone; Pyz = pyrazine; M = Fe and Mn) and exhibiting a 1D and 2D structure, respectively, have been studied. The 1D MOFs ({[M(L)(HO)]HO}n) show higher reversible capacity values for lithium ion insertion with respect to 2D structures containing two organic ligands (M(CA)(Pyz)]n). The gravimetric capacity for the 1D Fe-CA MOF is 75 mAh/g at 2.16 mA/g (∼ 1 lithium atom per formula unit) higher than for the Mn complexes which is 65 mAh/g at 2.12 mA/g, though isostructural. Lithium ion insertion in the 1D Mn-CA chains takes place at 2.4 V vs. Li/Li which is ∼700 mV higher than what is recorded for the Fe analogue. This result is most probably due to much more stable d electronic configuration of Mn than d of Fe in its isostructural Fe-based framework analogue of the final reduced phases. The 1D Fe-DHBQ capacity is higher than its manganese analogue 75 mAh/g at 2.5 mA/g (0.8 lithiums) against 40 mAh/g. In general, the high voltages of reaction in these 1D MOFs suggest that they involve the participation of the ligand on the redox processes along with the reduction of the transition metal if any. In fact, the potential of ion insertion changed depending on the metal. This fact along with the absence of evidence of conversion reaction by x-ray diffraction of cycled electrodes suggests that the charge delocalization may be all along the metal-ligand molecular framework participating as a whole hybrid unit in the lithium storage.

Iron(II) phthalocyanine (FePc) deposited onto two different car- bonaceous supports was synthesized through an unconven- tional pyrolysis-free method. The obtained materials were stud- ied in the oxygen reduction reaction (ORR) in neutral media through incorporation in an air-breathing cathode structure and tested in an operating microbial fuel cell (MFC) configura- tion. Rotating ring disk electrode (RRDE) analysis revealed high performances of the Fe-based catalysts compared with that of activated carbon (AC). The FePc supported on Black-Pearl carbon black [Fe-BP(N)] exhibits the highest performance in terms of its more positive onset potential, positive shift of the half-wave potential, and higher limiting current as well as the highest power density in the operating MFC of (243 7) mW cm2, which was 33 % higher than that of FePc support- ed on nitrogen-doped carbon nanotubes (Fe-CNT(N) ; 182 5 mW cm2). The power density generated by Fe-BP(N) was 92 % higher than that of the MFC utilizing AC ; therefore, the utilization of platinum group metal-free catalysts can boost the performances of MFCs significantly.

In this work, novel catalysts derived from iron and benzimidazole and aminobenzimidazole were synthesized using Sacrificial Support Method (SSM). The catalysts obtained were then tested in rotating ring disk electrode (RRDE) technique and compared with AC. Fe-based catalysts had performances much higher compared to AC and therefore are suitable for microbial fuel cell (MFC) applications. Future works will integrate the catalysts into air-breathing cathodes and test them in MFCs.