Immobilization of nanocatalysts on biochar is receiving unprecedented interest among material and catalysis scientists due to its simplicity, versatility, and high efficiency. Herein, we propose a new direct approach to obtain bimetallic copper/nickel nanoparticles loaded on olive stone biochar. The bimetallic-coated biochar and the reference materials, namely bare biochar, copper rich-loaded biochar, and nickel-loaded biochar, were prepared by pyrolysis from olive pit powder particles impregnated first with citric acid (CA) and then with copper and nickel nitrates at 400 °C under nitrogen flow. We employed citric acid in the process in order to examine its effect on the structural and textural properties of biochar supporting the metallic nanoparticles. Surprisingly, citric acid induced the formation of agglomerated or even raspberry-shaped bimetallic copper/nickel nanoparticles. Large 450–500 nm agglomerates of ~80 nm bimetallic CuNi NPs were noted for B-CA@CuNi. Interestingly, for biochar material prepared with initial Cu/Ni = 10 molar ratio (B-CA@CuNi_10/1), the bimetallic NPs formed unusual nanoraspberries (174 ± 8 nm in size), which were agglomerates of individual 10–20 nm CuNi_10/1 nanoparticles. The B-CA@CuNi and reference materials were characterized by Raman spectroscopy, scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and magnetometry. The B-CA@CuNi and B-CA@Ni materials could be efficiently attracted with a magnet but not B-CA@CuNi_10/1 due to the low nickel loading. B-CA@CuNi was tested as a catalyst for the degradation of methyl orange (MO). Discoloration was noted within 10 min, much faster than a similar material prepared in the absence of CA. B-CA@CuNi could be recycled at least 3 times while still exhibiting the same fast catalytic discoloration performance. This paper stresses the important role of citric acid in shaping bimetallic nanoparticles loaded in situ on biochar during the slow pyrolysis process and in enabling faster catalytic discoloration of organic dye solution.

Biochar is a carbon allotrope obtained by pyrolysis of biomass, usually agro-waste. Owing to the demand for sustainable development, biochar is continuously raising much hope in the scientific community. However, in order to impart it with new properties, its modification is required, either in situ during pyrolysis, or after the carbonization process. Herein, we propose a new direct approach to obtain bimetallic copper/nickel nanoparticle-loaded on olive stone biochar. The bimetallic-coated biochar and the reference materials bare biochar, copper-loaded and nickel-loaded biochar were prepared at 400 °C under a stream of dinitrogen from olive pit powder particles impregnated first with citric acid (CA), and then with copper and nickel nitrates. We have employed citric acid in the process in order to check its effect on the structural and textural properties of biochar supporting the metallic nanoparticles. Surprisingly, citric acid induced the formation of agglomerated or even raspberry-shaped, bimetallic copper/nickel nanoparticles. Large 450-500 nm-sized agglomerates of ~80 nm bimetallic CuNi NPs were noted for B-CA@CuNi. Interestingly, for biochar material prepared with initial Cu/Ni=10 molar ratio (B-CA@CuNi10/1), the bimetallic NPs formed unusual nano-raspberries (1748 nm in size) which are agglomerates of individual 10-20 nm-sized CuNi10/1 nanoparticles. The B-CA@CuNi and reference materials were characterized by Raman spectroscopy, scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and magnetometry. The B-CA@CuNi and B-CA@Ni materials could be attracted efficiently with a magnet, but not B-CA@CuNi10/1 due to a low nickel loading. B-CA@CuNi was tested as a catalyst for the degradation of methyl orange (MO). Discoloration was noted within 10 min, much faster than a similar material prepared in the absence of CA. B-CA@CuNi could be recycled at least 3 times with exhibit as fast discoloration catalysis performance. This paper stresses the important role of citric acid in shaping the bimetallic nanoparticles loaded in situ on biochar during the slow pyrolysis process and to enable faster catalysed discoloration of organic dye solution.

Water treatment is one of the most research-challenging areas, and continuously requires the development of efficient sustainable materials for catalytic total mineralization of organic compounds. Herein, Moringa oleifera biomass was converted to "black gold" biochar loaded with ZnO nanoparticles (MOFB@ZnO) by slow pyrolysis, at 500 °C under an inert atmosphere, (MOFB@ZnO). This composite catalyst was used for the total degradation of Congo Red, a model organic pollutant. SEM confirmed the uniform distribution of ZnO nanoparticles, while XPS and XRD indicated the presence of ZnO, primarily in the wurtzite crystalline structure. Optimization was conducted using the central composite design (CCD) method and STATISTICA 12.0 software. The composite catalyst was applied in the electrochemical degradation of Congo Red dye, using a platinum anode and a carbon felt cathode to generate H2O2 from O2 reduction. The ZnO-decorated Moringa oleifera biochar catalyst permitted to achieve of 98% removal of total organic carbon in less than 6h. It is 10-fold more efficient than pristine biochar and can be recycled up to 4 times without any significant loss. The process is highly efficient producing sustainable low-cost catalysts for water purification from organics, and contributes to sustainable chemical processes therefore addressing SDGs 6, 9, and 13.

Compositing and hybridizing compounds is a generally accepted route to making new materials that perform better than the individual components taken separately. Herein, we describe a new electrochemical route for constructing hybrid materials from Polypyrrole (PPy). In this context, thin films of silica layer (Si) deposited by electro-assisted on a flexible ITO (f-ITO) surface modified by diazonium salt (f-ITO-NH2) were covered with an adhesive layer of polypyrroles. Deposition periods ranging from 20 to 45 seconds produce more electroactive silica layers. The electrochemical method confirmed the growth of a silica layer on the surface of the f-ITO-NH2 electrode. The different flexible electrodes were characterized by XPS, by electrochemical and scanning electron microscopy (SEM), which showed the central role of the diazonium chemical interface in the development of PPy on the silica layer. According to cyclic voltammetric studies, altering the f-ITO surface with diazonium salts produces PPy-Si polymers with more conductivity than a comparable coating without integrated treatment. This work demonstrates the power of a subtle combination of diazonium coupling agents on f-ITO, silica layer, and conductive polymers (f-ITO-NH2-Si-PPy) to design high-performance electrochemical materials.