Metal-free catalysis for electrocatalytic hydrogen evolution from water is very demanding for the production of sustainable and clean fuel. Herein, we report the synthesis of a porphyrin-based metal-free covalent organic polymer (TpPAM) through a simple condensation between triformyl phloroglucinol (Tp) and 5,10,15,20-tetra(4-aminophenyl)-21H,23H-porphyrin (PAM). The as-prepared porous TpPAM exhibited superior activity for the hydrogen evolution reaction (HER) current density of 10 mA cm −2 at a low overpotential of 250 mV and a small Tafel slope of 106 mV decade −1 , which are better than those of related metal-free electrocatalysts. The high HER activity of TpPAM was investigated in-depth via theoretical density functional theory (DFT) calculations. The theoretical findings were correlated with the experimental results, and these were in good agreement for high HER catalytic efficiency of the porous TpPAM polymer. The Faradaic efficiency of the TpPAMbased electrode was found to be 98%, which is very close to the ideal value of 100%, reflecting its potential for practical implementation. Moreover, the as-synthesized catalyst showed good stability by retaining 91% of the initial current density after 1000 cycles.

In this study, BiVO4 was prepared by a hydrothermal synthesis route in the presence of sodium dodecyl sulfate using aqueous NH3 as precipitant. g-C3N4 was prepared by a combustion method using melamine. In order to develop highly efficient photocatalyst, a heterojunction catalyst based on g-C3N4 and BiVO4 was prepared. Different amounts of BiVO4 and g-C3N4 were mixed and annealed to obtain heterojunction photocatalysts. FeVO4 and LaVO4 were also prepared for the comparative catalytic investigation. Catalysts were characterized by a series of complementary combinations of powder X-ray diffraction, thermogravimetric analysis, elemental analysis, N2 adsorption–desorption, scanning electron microscopy, transmission electron microscopy, temperature-programmed desorption of NH3 and CO2, diffuse reflectance ultraviolet visible spectroscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, and photoelectrochemical studies. Catalysts were investigated in the visible light driven oxidation of benzyl alcohol, benzyl amine, and aniline with O2. In order to propose the electrons, holes, and radicals mediated reaction pathways, reactions were performed in the presence of an electron/hole/radical scavenger. Further, in order to confirm various products formed during the photocatalytic oxidation of benzyl alcohol, benzyl amine, and aniline, several model reactions were carried out. Based on the results obtained, the reaction mechanism and structure–activity relationship were established.

We report the synthesis of a new benzimidazole-based covalent organic polymer (TpDAB) via solvothermal Schiff base condensation between 1,3,5-triformylphloroglucinol (Tp) and 3,3'-diaminobenzidine (DAB). TpDAB showed high energy storage capacity with a specific capacitance of 335 F g(-1) at 2 mV s(-1) scan rate and good cyclic stability with 93% retention of its initial specific capacitance after 1000 cycles.

Microbial fuel cells (MFCs) are emerging as a sustainable technology for waste to energy conversion where electrode materials play a vital role on its performance. Platinum (Pt) is the most common material used as cathode catalyst in the MFCs. However, the high cost and low earth abundance associated with Pt prompt the researcher to explore inexpensive catalysts. The present study demonstrates a noble metal-free MFC using a manganese ferrite (MnFe2O4)/polyaniline (PANI)-based electrode material. The MnFe2O4 nanoparticles (NPs) and MnFe2O4 NPs/PANI hybrid composite not only exhibited superior oxygen reduction reaction (ORR) activity for the air cathode but also enhanced anode half-cell potential upon modifying carbon cloth anode in the single-chambered MFC. This is attributed to the improved extracellular electron transfer of exoelectrogens due to Fe(3+) in MnFe2O4 and its capacitive nature. The present work demonstrates for the first time the dual property of MnFe2O4 NPs/PANI, i.e., as cathode catalyst and an anode modifier, thereby promising cost-effective MFCs for practical applications.

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