From chicken feather to nitrogen and sulfur co-doped large surface bio-carbon flocs: an efficient electrocatalyst for oxygen reduction reaction

Investigating the properties and agronomic benefits of onion peel and chicken feather-derived biochars

Biochar production from unconventional biomass, specifically onion peel (OP) and chicken feathers (CF), was investigated in this study. Two distinct biochars were produced by doping each biomass with the other, with the aim of exploring the synergistic effects of different feedstock combinations on biochar properties. The biochar production process was conducted using a retort heating method and characterized using several techniques. A yield of 36 % was obtained for OP-doped biochar (OP92CF8-BC) and 23 % for CF-doped biochar (F92OP8-BC). Fourier Transform Infrared Spectroscopy analysis revealed characteristic functional groups from cellulose, hemicellulose, and lignin in OP92CF8-BC, while CF92OP8-BC displayed keratin-related peaks. Scanning Electron Microscopy imaging showed surface morphology differences, with OP92CF8-BC exhibiting a rougher and more porous structure compared to CF92OP8-BC. Energy-Dispersive X-ray Spectroscopy analysis confirmed the elemental composition, with OP92CF8-BC having higher carbon, calcium, and sulfur contents and CF92OP8-BC having higher nitrogen and oxygen contents. The biochar had specific surface areas of 342.4 and 200.80 m2/g for OP92CF8-BC and CF92OP8-BC, respectively. According to the results, using biochar treatments-more especially, CF92OP8-BC-can significantly enhance cob weight. This could be good for agricultural productivity. These findings highlight the influence of feedstock composition on the properties of biochar and provide insights for its potential applications in soil amendment and pollutant removal.

Study on H2SO4-modified corn straw biochar as substrate material of constructed wetland

The high value resource utilization of corn straw is a long-term problem at present and in the future. Biochar preparation is an important utilization way of corn straw. The research on city tail water treated by constructed wetland (CW) with biochar was carried out to further increase the wastewater treatment capacity of the CW. Surface characterization, structural characteristics, and adsorption of straw biochar modified by different acids were measured. The study found that the ability of H2SO4 to remove ash from biochar was stronger than other acids and H2SO4-biochar was easy to be cleaned without H2SO4 residue. The performance of biochar modified by H2SO4 was obviously better than other acids, and the biochar adsorption was enhanced. The modification of biochar substrate modified by H2SO4 in CW reduced the change of electrical conductivity (EC) and promoted denitrification. H2SO4-modified biochar promoted the absorption of N and P by Iris pseudacorus L. The compound modification effect of straw biochar was obvious. The results revealed the acid modification characteristics of straw biochar, which were beneficial for increasing the wastewater treatment rate by CW. This study will promote the sustainable development of CW.

Giving New Life to Waste Cigarette Butts: Transformation into Platinum Group Metal-Free Electrocatalysts for Oxygen Reduction Reaction in Acid, Neutral and Alkaline Environment

Following the core theme of a circular economy, a novel strategy to upcycle cigarette butt waste into platinum group metal (PGM)-free metal nitrogen carbon (M-N-C) electrocatalysts for oxygen reduction reaction (ORR) is presented. The experimental route was composed of (i) the transformation of the powdered cigarette butts into carbonaceous char via pyrolysis at 450 °C, 600 °C, 750 °C and 900 °C, (ii) the porosity activation with KOH and (iii) the functionalization of the activated chars with iron (II) phthalocyanine (FePc). The electrochemical outcomes obtained by the rotating disk electrode (RRDE) technique revealed that the sample pyrolyzed at 450 °C (i.e., cig_450) outperformed the other counterparts with its highest onset (Eon) and half-wave potentials (E1/2) and demonstrated nearly tetra-electronic ORR in acidic, neutral and alkaline electrolytes, all resulting from the optimal surface chemistry and textural properties.

Lignin-based nitrogen/sulfur dual-doped nanosheets decorated with Co1-xS nanoparticles as efficient bifunctional oxygen electrocatalysts

The development of efficient, cost-effective, bifunctional cathode catalyst materials to replace precious metals is highly attractive for the fabrication of Zn-air battery. Here, the three-dimensional N and S co-doped carbon nanosheets loaded with cobalt sulfide nanoparticles (Co_1-xS@SNFC) for bifunctional oxygen electrocatalysis were synthesized with Co(NO₃)₂·6H₂O as the Co source, lignin as the carbon source, thiourea as the nitrogen/ sulfur source, and MgO as the template. The synergistic effect of multiple active sites gives the Co_1-xS@SNFC fast electrochemical kinetic properties and excellent stability to oxygen reduction reactions (ORR) and oxygen evolution reactions (OER). The half-wave potential and overpotential of Co_1-xS@SNFC were 0.84 mV and 306 mV, respectively, which is closed to commercial noble metal catalysts. In addition, Co_1-xS@SNFC exhibited four-electron transfer characteristics and ultra-low tafel slope. Compared with commercial Pt/C, the Zn-air battery assembled from Co_1-xS@SNFC exhibited a low voltage gap of polarization curve (0.75 V) between charging and discharge and high power density (207 mWcm^-2) in alkaline electrolyte. This work developed a green and novel fabrication approach for the synthesis of bifunctional electrocatalyst and provides a new idea for high-value utilization of biomass.

Awn Stem-Derived High-Activity Free-Metal Porous Carbon for Oxidation Reduction

Designing oxygen reduction reaction (ORR) catalysts with excellent performance has far-reaching significance. In this work, a high-activity biomass free-metal carbon catalyst with N and S co-doped was successfully prepared by using the KOH activated awn stem powder as the precursor with organic matter pore-forming doping technology, which is named TAAS. The content of pyridine nitrogen groups accounts for up to 36% of the total nitrogen content, and a rich pore structure is formed on the surface and inside, which are considered as the potential active centers of ORR. The results show that the specific surface area of TAAS reaches 191.04 m²/g, which effectively increases the active sites of the catalyst, and the initial potential and half slope potential are as high as 0.90 and 0.76 V vs. RHE, respectively. This study provides a low-cost, environmentally friendly and feasible strategy for the conversion of low-value agricultural and forestry wastes into high value-added products to promote sustainable development of energy and the environment.

Bioanodes containing catalysts from onion waste and Bacillus subtilis for energy generation from pharmaceutical wastewater in a microbial fuel cell

Performance of the FAOW8 + B. subtilis bioanode in an MFC (a 14-day test) using pharmaceutical wastewater (pH = 9.2) as a substrate.

Optimization Strategies of Preparation of Biomass-Derived Carbon Electrocatalyst for Boosting Oxygen Reduction Reaction: A Minireview

Oxygen reduction reaction (ORR) has attracted considerable attention for clean energy conversion technologies to reduce traditional fossil fuel consumption and greenhouse gas emissions. Although platinum (Pt) metal is currently used as an electrocatalyst to accelerate sluggish ORR kinetics, the scarce resource and high cost still restrict its further scale-up applications. In this regard, biomass-derived carbon electrocatalysts have been widely adopted for ORR electrocatalysis in recent years owing to their tunable physical/chemical properties and cost-effective precursors. In this minireview, recent advances of the optimization strategies in biomass-derived carbon electrocatalysts towards ORR have been summarized, mainly focusing on the optimization of pore structure and active site. Besides, some current challenges and future perspectives of biomass-derived carbon as high-performance electrocatalysts for ORR have been also discussed in detail. Hopefully, this minireview will afford a guideline for better design of biomass-derived carbon electrocatalysts for ORR-related applications.

Enhanced adsorption of Pb(II) by nitrogen and phosphorus co-doped biochar derived from Camellia oleifera shells

We describe the synthesis of a series of novel nitrogen- and phosphorus-enriched biochar (activated carbon, AC) nanocomposites via the co-pyrolysis of Camellia oleifera shells (COSs) with different weight ratios of ammonium polyphosphate (APP) (w_APP: w_COSs = 1-3:1). The physicochemical characteristics of these nanocomposites (APP@ACs) were investigated via X-ray diffraction (XRD), Raman spectroscopy, N₂ adsorption/desorption analysis, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). The results revealed that the APP@ACs exhibited richer N- and P-containing functional groups than unmodified AC. In addition, the removal performance of APP@AC-3 with respect to Pb(II) (723.6 mg g^-1) was greatly improved relative to unmodified AC (264.2 mg g^-1). Kinetic and equilibrium data followed the pseudo-second-order kinetic model and Langmuir model, respectively. The removal mechanism could be attributed to partial physisorption and predominant chemisorption. The N₂ adsorption/desorption isotherms demonstrated that pore-volume properties could be an effective physical trap for Pb(II). Furthermore, the XPS and FTIR analysis revealed that the chemical removal mechanism of the APP@ACs is surface complexation via N-containing and P-containing functional groups. These findings indicate that the co-pyrolysis of COSs and APP leads to the formation of nitrogen- and phosphorus-containing functional groups that facilitate excellent activated carbon-based (biochar) adsorption performance.

Removal of Zn(II), Mn(II) and Cu(II) by adsorption onto banana stalk biochar: adsorption process and mechanisms

Low-cost banana stalk (Musa nana Lour.) biochar was prepared using oxygen-limited pyrolysis (at 500 °C and used), to remove heavy metal ions (including Zn(II), Mn(II) and Cu(II)) from aqueous solution. Adsorption experiments showed that the initial solution pH affected the ability of the biochar to adsorb heavy metal ions in single- and polymetal systems. Compared to Mn(II) and Zn(II), the biochar exhibited highly selective Cu(II) adsorption. The adsorption kinetics of all three metal ions followed the pseudo-second-order kinetic equation. The isotherm data demonstrated the Langmuir model fit for Zn(II), Mn(II) and Cu(II). The results showed that the chemical adsorption of single molecules was the main heavy metal removal mechanism. The maximum adsorption capacities (mg·g^-1) were ranked as Cu(II) (134.88) > Mn(II) (109.10) > Zn(II) (108.10)) by the single-metal adsorption isotherms at 298 K. Moreover, characterization analysis was performed using Fourier transform infrared spectroscopy, the Brunauer-Emmett-Teller method, scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results revealed that ion exchange was likely crucial in Mn(II) and Zn(II) removal, while C-O, O-H and C = O possibly were key to Cu(II) removal by complexing or other reactions.

A non-traditional biomass-derived N, P, and S ternary self-doped 3D multichannel carbon ORR electrocatalyst

A synthetic non-traditional biomass-derived ORR catalyst is developed to overcome traditional shortcomings, that is, the existence of solid micron blocks and fewer heteroatoms.

Studies on durability of sustainable biobased composites: a review

This review provides a comprehensive discussion on the long-term durability performance and degradation behaviour of the increasingly popular sustainable biobased composites under various aging environments.

Adsorption of cadmium and lead ions by phosphoric acid-modified biochar generated from chicken feather: Selective adsorption and influence of dissolved organic matter

To improve the adsorption efficiency, a H₃PO₄-modified biochar (CFCP) was prepared using chicken feather and applied to Cd²⁺ and Pb²⁺ adsorption. The pseudo-second-order model could explain the Cd²⁺ and Pb²⁺ adsorption behavior. CFCP had faster adsorption rate than non-modified biochar (CFC2). The Langmuir and Freundlich isotherm could better describe the Cd²⁺ and Pb²⁺ adsorption, respectively. The value of q_m for Cd²⁺ adsorption and K_F for Pb²⁺ adsorption by CFCP was 7.84 mg·g^-1 and 24.41 mg^1-(1/n)·L^1/n·g^-1, which was 1.38 and 5.41 times of the corresponding results of CFC2. Relative to Cd²⁺, Pb²⁺ was selectively adsorbed by biochars in the binary metal system. Phosphate precipitation explained in part the selective adsorption of Pb²⁺. Proline, glucose, and pH (4-6) had little influence on Cd²⁺ and Pb²⁺ adsorption. Electrostatic interaction, precipitation, and O-H bonds were the primary adsorption mechanisms. The increased N-containing heterocycles of CFCP accounted for the increased Cd²⁺ and Pb²⁺ adsorption.

Marine Algae-Derived Porous Carbons as Robust Electrocatalysts for ORR

Large quantities of marine algae are annually produced, and have been disposed or burned as solid waste. In this work, porous carbons were prepared from three kinds of marine algae (Enteromorpha, Laminaria, and Chlorella) by a two-step activation process. The as-prepared carbon materials were doped with cobalt (Co) and applied as catalysts for oxygen reduction reaction (ORR). Our results demonstrated that Co-doped porous carbon prepared from Enteromorpha sp. (denoted by Co-PKEC) displayed excellent catalytic performance for ORR. Co-PKEC obtained a half-wave potential of 0.810 V (vs. RHE) and a maximum current density of 4.41 mA/cm2, which was comparable to the commercial 10% Pt/C catalyst (E1/2 = 0.815 V, Jd = 4.40 mA/cm2). In addition, Co-PKEC had excellent long-term stability and methanol resistance. The catalytic ability of Co-PKEC was evaluated in a one-chamber glucose fuel cell. The maximum power density of the fuel cell equipped with the Co-PKEC cathode was 33.53 W/m2 under ambient conditions, which was higher than that of the fuel cell with a 10% Pt/C cathode. This study not only demonstrated an easy-to-implement approach to prepare robust electrochemical catalyst from marine algal biomass, but also provided an innovative strategy for simultaneous waste remediation and value-added material production.

Catalytic Activity of Bimetallic (Ruthenium/Palladium) Nano-alloy Decorated Porous Carbons Toward Reduction of Toxic Compounds

Chicken feather-derived high-surface-area porous activated carbon (CFAC) material was prepared using chemical activation. A new composite composed of Ru-Pd nanoparticles supported on CFAC (Ru-Pd@CFAC) has been prepared by microwave-thermal reduction in the presence of the support. Characterization by XRD, Raman, BET, FE-SEM/TEM, FT-IR, TGA, XPS, HAADF-STEM-EDS, H₂ -chemisorption, H₂ -TPR, and ICP-AES was used to analyze the catalyst. This catalyst is found to be efficient for the reduction of hexavalent chromium (Cr^VI ), potassium ferricyanide (K₃ [Fe(CN)₆ ]), 4-nitrophenol (4-NP), and pendimethalin (PDM), at room temperature, and remains stable, even after several repeated runs. Moreover, it showed excellent catalytic activity compared with the monometallic counterparts.

Electrical Conductivity of Films Formed by Few-Layer Graphene Structures Obtained by Plasma-Assisted Electrochemical Exfoliation of Graphite

Current-voltage characteristics of few-layer graphene structures (FLGS) obtained by plasma-assisted electrochemical exfoliation of graphite in Na2SO4 solution were measured. FLGS are shown to possess electronic conductivity, which indicates the predominant functionalization of the edges of graphene planes and the preservation of the structure of basal planes in obtained nanostructures as in the source graphite. The effect of humidity on the conductivity of FLGS films was studied. The resistance of films was found to increase with an increase in the relative humidity of the environment due to the shielding of FLGS flakes by a film of water. The effect of different solvents on the current-voltage characteristics of FLGS was analyzed. The conductivity of films significantly decreased in vapors of polar protic solvents, while there was a minor effect of nonpolar aprotic solvents on the conductivity of FLGS films.

N-Doped Porous Carbon from Sargassum spp. as Efficient Metal-Free Electrocatalysts for O2 Reduction in Alkaline Fuel Cells

This work reports the synthesis of N-doped porous carbon (NPC) with a high surface area from Sargassum spp. as a low-cost alternative for electrocatalyst production for the oxygen reduction reaction (ORR). Sargassum spp. was activated with potassium hydroxide at different temperatures (700, 750, and 800 °C) and then doped with pyridine (N700, N750, and N800). As a result of the activation process, the 800 °C sample showed a high surface area (2765 m2 g−1) and good onset potential (0.870 V) and current density (4.87 mA cm−2). The ORR performance of the electrocatalysts in terms of their current density was N800 > N750 > N700 > 750 > 800 > 700, while the onset potential decreased in the following order: N800 > 800 > 750 > 700 > N700 > N750. The fuel cell performance of the membrane electrode assembly (MEA) prepared with electrocatalyst synthesized at 750 °C and doped with pyridine was 12.72 mW cm−2, which was close to that from Pt/C MEA on both the anode and cathode (14.42 mW cm−2). These results indicate that NPCs are an alternative to the problem of Sargassum spp. accumulation in the Caribbean due to their high efficiency as electrocatalysts for ORR.

Advanced Biomass-Derived Electrocatalysts for the Oxygen Reduction Reaction

Recent progress in advanced nanostructures synthesized from biomass resources for the oxygen reduction reaction (ORR) is reviewed. The ORR plays a significant role in the performance of numerous energy-conversion devices, including low-temperature hydrogen and alcohol fuel cells, microbial fuel cells, as well as metal-air batteries. The viability of such fuel cells is strongly related to the cost of the electrodes, especially the cathodic ORR electrocatalyst. Hence, inexpensive and abundant plant and animal biomass have become attractive options to obtain electrocatalysts upon conversion into active carbon. Bioresource selection and processing criteria are discussed in light of their influence on the physicochemical properties of the ORR nanostructures. The resulting electrocatalytic activity and durability are introduced and compared to those from conventional Pt/C-based electrocatalysts. These ORR catalysts are also active for oxygen or hydrogen evolution reactions.

The thermochemical conversion of non-lignocellulosic biomass to form biochar: A review on characterizations and mechanism elucidation

Biochar obtained from non-lignocellulosic biomass (NLBM) has attracted wide interests in various fields like pollutants removal, catalysis, and energy storage. However, the thermochemical conversion processes from NLBM to non-lignocellulosic biochar (NLBC) have not been well summarized until now. To fill the knowledge gap, this review presents a systematical summary of NLBM characteristics, thermochemical behaviors of main components (e.g., C, O, N, P and metals), characterization methods for NLBC and conversion process, and the main applications of NLBC. Moreover, the vacancy and limitations of the current researches are pointed out to provide some guidance for future study. This review would contribute to deepen the understanding of NLBC, meanwhile optimize the efficient disposal and value-added utilization of NLBM wastes via thermochemical conversion.

Simple Fabrication of Titanium Dioxide/N-Doped Carbon Hybrid Material as Non-Precious Metal Electrocatalyst for the Oxygen Reduction Reaction

We report a new approach for the fabrication of hybrid titanium dioxide/carbon materials derived from a porous titanium coordination polymer composed of a catechol-substituted porphyrin and Ti⁴⁺. Titanium dioxide nanocrystals were formed distributed in a nitrogen-doped carboniferous matrix after the thermolysis of the coordination polymer. The identity of the titanium dioxide phase, i.e., anatase or rutile, could be controlled by varying the thermolysis temperature. Electrochemical performances of the composites were explored with results demonstrating that the hybrid materials are promising cathodic materials for the oxygen reduction reaction.