Lack of control over the structure and electrically nonconductive properties of coordination polymers (CPs) creates a major hindrance to designing an active electrocatalyst for oxygen reduction reaction (ORR). Here, we report a new semiconductive and low-optical band gap CP structure [{Co 3 (μ 3 -OH)(BTB) 2 (BPE) 2 }{Co 0.5 N(C 5 H 5 )}], 1 , that exhibits high-performance ORR in alkaline medium. The electrical conductivity of compound 1 was measured using impedance spectroscopy and found to be 5 × 10 –4 S cm –1 . The Ketjenblack EC-600JD carbon used as a support for all the electrochemical methods such as cyclic voltammetry, rotating disk electrode, rotating ring-disk electrode and Koutecký–Levich analysis. The as-synthesized Co-based catalyst has the ability to reduce O 2 to H 2 O by a nearly four-electron process. The crystal structure of 1 shows that the trimeric unit {Co 3 (μ 3 -OH)(COO) 5 N 3 } and monomeric unit {Co(COO) 2 (NC 5 H 4 ) 2 } 2+ are linked with BTB and BPE linkers to form a three-dimensional structure. Theoretical calculations predict that the monomeric center acts as an active catalytic site for ORR. This could be due to the efficient overlap of highest occupied molecular orbital–lowest unoccupied molecular orbital between monomer and O 2 molecule. This CP, 1 , shows facile 3.6-electron ORR, and it is inexpensive compared with widely used Pt catalysts. Therefore, this CP can be used as a promising cathode material for fuel cells in terms of efficiency and cost effectiveness.

Tuning the electronic structure of perovskite oxides via aliovalent substitution is a promising strategy to attain inexpensive and efficient electrocatalysts for energy conversion and storage devices. Herein, following the d-band center positions and using a simple sol–gel method followed by a pyrolysis step, LaNi1–x Co0.5x Fe0.5x O3 (LNFCO-x; x = 0.0, 0.4, 0.5, and 0.6) electrocatalysts are designed and synthesized for oxygen redox reactions in 1 M KOH. Among them, LNFCO-0.5 has exhibited the lowest overpotential and the highest charge transfer kinetics in oxygen redox reactions. Overall, a 90 mV lower overpotential was observed in oxygen redox activity of LNFCO-0.5 compared to that of pristine LaNiO3. The mass activity of LNFCO-0.5 in the oxygen reduction reaction (at 0.7 V vs RHE) and oxygen evolution reaction (1.60 V vs RHE) was calculated to be 2.5 and 2.13 times higher than that of LaNiO3, respectively. The bifunctionality index (potential difference between the oxygen evolution at a current density of 10 mA cm–2 and the oxygen reduction at a current density of −1 mA cm–2) of LNFCO-0.5 was found to be 0.98. The substitution of Fe and Co for the Ni-site shifted the d-band center close to the Fermi level, which can increase the binding strength of the *OH intermediate in the rate-determining step. Also, the surface was enriched with Fe3+Δ, Co3+, and partially oxidized Ni3+ states, which is susceptible to tune the eg-orbital filling for superior oxygen redox activity.

Single Crystal X-ray Diffraction Analysis: Table S1: Single Crystal Data and Refinement Results for Ni-BTB-BPE.* Parameters Compound 1 Chemical formula Ni 1.5 C 57 N 6 O 10.5 H 41 Formula weight 1066.02 Crystal system Monoclinic Space Group P2 1 /n a(Å) 8.6003 (2) b(Å) 18.6486 (5) c(Å) 34.7689 (9) α(⁰) 90 β(⁰) 96.7110 (10) γ(⁰) 90 Volume (Å 3) 5538.2 Z 4 Temperature (K) 150 Calculated density (g/cm 3) 1.279 θ range (⁰) 2.359 to 28.324 Absorption coefficient (mm-1) 0.577 Reflections collected 51299 Unique reflections 13628 Goodness-of-fit 0.994 Number of parameters 689 Final R indices [I > 2sigma(I)] R 1 = 0.0695, wR 2 = 0.1872 [a] R1 = F 0 -F c / F 0 ; wR 2 = {[w(F 0 2-F c 2) 2 ]/ [w(F 0 2) 2 ]} 1/2 ; w = 1/[σ 2 (F 0) 2 + (aP) 2 + bP];P = [max(F 0 2 ,0) + 2(F c) 2 ]/3; a = 0.1293 , b = 0.0000 *Recently the structure of this compound was reported by us (CCDC no. 1854511).

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Recently, pyrolyzed transition metal-carbon-nitrogen based non-precious metal (NPM) catalysts are envisioned as promising alternatives to metal catalysts. However, the precise active site in these NPM catalysts remains elusive, as their surface composition is heterogeneous in nature. Lack of understanding on the electrocatalytic active site for the oxygen reduction reaction (ORR) is one of the fundamental obstacles in design and synthesis of the catalyst. In this study, carbon supported metal–organic complexes,[Co(bpy)3](NO3)2 and [Co(bpy)2NO3]NO3 · 5H2O (where, bpy is 2,2’-Bipyridine) are shown to perform ORR in 0.1 N KOH. Replacement of one of the bipyridine of [Co(bpy)3]2 + with NO−3, yields a catalyst, [Co(bpy)2NO3]+ with improved ORR kinetics. The NO−3 ligand influence on the reduction of the oxygen studied using the linear sweep voltammograms obtained using rotating disc electrode, rotating ring-disc electrode and Tafel analysis. The Tafel slope and exchange current density measured on [Co(bpy)2NO3]NO3 · 5H2O and [Co(bpy)3](NO3)2 are 105 mV dec−1, 2 × 10−4 mA cm−2 and 120 mV dec−1, 4 × 10−4 mA cm−2 respectively. Turn-over frequency (ToF) of these complexes estimated to understand the extent of selectivity of these complexes toward 2- and 4-electron reduction of O2.

A new, simple, green method for the synthesis of Au nanowires (average diameter 8 nm and several micrometers in length) using Au seeds prepared from bael gum (BG) is reported. The nanowires are characterized using UV−visible absorption spectroscopy, powder X-ray diffraction, transmission electron microscopy (TEM), and high-resolution-TEM. It is observed that the rate of the reduction process might be the decisive factor for the shape selectivity, as evident from the formation of nanowires at a particular concentration of seeds and NaOH. The polysaccharide present in BG is the active ingredient for the synthesis of Au nanowires, while the small molecules present in BG, when used alone, did not result in nanowire formation. The TEM images of the precursor to the Au nanowires suggested that new, nucleated particles align in a linear manner and fuse with one another, resulting in the nanowire. The linear fusion of the newly nucleated particles could be due to the lack of adequate protecting agent and the presence of Au complex adsorbed to the surface. The electrochemical activity of the nanowires for oxygen reduction reaction (ORR) is assessed and compared with that of nanotriangles and spherical nanoparticles of Au. The performance of Au nanowire is better than Au-nanomaterials (heat-treated as well as non-heat-treated), Au seeds, and clusters. The better efficiency of the nanowires when compared to that of the other reported catalysts is attributed to the presence of active (100) facets with numerous corners, edges, and surface defects.

Non-precious metal electrocatalysts obtained by pyrolysis of precursors of metal, nitrogen, and carbon (MNC) are viewed as an inexpensive replacement for platinum-based electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells. The hypothesized ORR active site structure of typical MNC catalysts consists of a transition metal coordinated to the pyridinic/pyrollic type of nitrogen covalently attached to the edges of the graphitic crystallites. One of the drawbacks of all the reported procedures to synthesize these MNC electrocatalysts is the inability to control the formation of a specific active site structure suitable for ORR. Lack of clarity on the active site structure limits the researcher's ability to design a synthesis methodology that maximizes the specific active site density. In this study, we have synthesized a Co(III) dimer ([Co 2 (OH) 2 (OOCCH 3 ) 3 (bpy) 2 ] NO 3 ⋅ 1.5 H 2 O) and demonstrated its ORR activity in alkaline medium. The ORR activity and methanol tolerance property of the Co(III) dimer were compared with those of Ketjenblack carbon (used as support for Co(III) dimer) and commercial 20 wt% Pt/C, respectively. Since Co(III) dimer is a molecular material, its characterization by single-crystal X-ray diffraction, nuclear magnetic resonance, and infrared studies revealed the chemical structure unambiguously. Density functional theory calculation predicted the possibility of both end-on and side-on oxygen adsorption at the metal center of the Co(III) dimer.

A non-polymer crystalline organoboron electrolyte results in the formation of nano-channels for directional conduction of Li ions, owing to presence of boron, allowing Lewis acid–base interaction.