Lower Charge Transfer Resistance Research Articles

Hierarchical CaZrO3@rGO nanostructure as an electrode material for high-performance supercapacitor devices

The primary focus of energy-storage system development is to find cost-effective solutions that improve performance, efficiency and stability. The electrode composed of CaZrO3 nanoparticles supported by reduced graphene oxide demonstrates higher capacitance and long-term cyclic stability. In this work, CaZrO3@rGO nanocomposite synthesized through a hydrothermal approach exhibited a specific capacitance of 1564 F/g @ 1 A/g with lower charge transfer resistance of 0.2 Ω which showed cyclic stability after 10,000th cycles. Due to the increased surface area and enrichment of active zones, the capacitive properties of the electrode are greatly improved when metal oxides are combined with rGO. Based on these results, it seems that CaZrO3@rGO nanocomposite may be used for future energy-saving equipment.

Improving Scalability of copper recovery in saline microbial fuel cells with microtubular polypyrrole-based cathodic electrocatalysts

Microbial fuel cells (MFC) are emerging energy-efficient systems for copper (Cu) electrowinning from waste streams by coupling it with anodic oxidation of organics in wastewater. However, there is a lack of research examining scalable electrocatalysts for Cu electrowinning at low cathodic overpotentials in highly saline catholytes often found in e-waste leachates. The challenge of developing resilient anodic biofilms that withstand the antagonistic effects of ions migrating from catholytes in saline MFC also needs to be addressed. In this study, polypyrrole (PPy) cathodic electrocatalysts were developed and coupled with a robust halophilic anodic biofilm in MFC to improve the kinetics of Cu electrowinning from acidic chloride-based catholytes. Electrochemical characterisation of these cathodes revealed shuttling of electrons by redox-active PPy via the formation of intermediate Cu+-complexes as an energy-efficient pathway for producing metallic Cu. High power densities ranging from 0.63 ± 0.17 to 0.73 ± 0.05 W m−2 were achieved with undoped-PPy and phytic acid doped-PPy cathodes with simultaneous recovery of ∼97% Cu. These electrocatalysts also exhibited low charge transfer resistance (3–8 mΩ m2) that met the requisites for scalable cathodes in MFC. However, a decrease in the efficiency of PPy cathodes was observed over 5 d due to competing reactions at their interfaces, including re-oxidation of deposited Cu and cathodic corrosion, with further studies suggested to enhance their corrosion resistance. Nonetheless, integrating PPy electrocatalysts for Cu electrowinning in saline MFC has advanced its outlooks as an energy-efficient downstream process for urban mining of Cu from e-waste.

Electrodeposited polyaniline modified CNT fiber as efficient counter electrode in flexible dye-sensitized solar cells

Carbon-based electrodes played a significant role toward the development of wearable and flexible photovoltaic energy devices in an efficient and affordable manners. Here, all-carbon-based electrodes composed of carbon nanotubes fiber (CNTF) have been used to fabricate a flexible wire shaped dye-sensitized solar cell (DSSC). A facile electrodeposited approach has been adopted to modify a CNTF with polyaniline (PANI) under acidic conditions. Both photoanode (TiO2@CNTs) and counter electrode (PANI@CNTs) twisted around each other, acted as electrons and hole collectors in the presence of redox couple (iodide/triiodide) as electrolyte. Scanning electron microscopy (SEM) images demonstrated the successful growth of TiO2 nanoparticles and conducting polyaniline (PANI) over the surface of CNTs fibers, as photoanode and counter electrode, respectively. Cyclic voltammetric (CV) measurements and electrochemical impedance spectroscopy (EIS), examined the reduction of triiodide and resistance of charge transfer. While the current-voltage measurements were carried out to check the performance of fabricated device when illuminated under simulated light source. With APNI modified counter electrode, device exhibited higher photoelectric conversion efficiency (3.57 %) under optimal conditions as compared to pristine CNTs fiber-based device with lower efficiency (2.26 %). The improved performance of modified counter electrode further confirmed by the lower peak separation (ΔEp= 0.42 V) and charge transfer resistance (RCE =19.28 Ω) in cyclic voltammetry and impedance spectroscopy, respectively. These fabricated electrodes could be promising alternate for metal-based electrodes in dye-sensitized solar cells due to its facile fabrication process, low cost, and higher chemical stability.

Comparative role of Ag and Ce doping on WO3 and GO modified nanostructures for bi-functional effective photocatalyst and electro catalyst

The comparative study of Ag and Ce doped WO3 modified with GO ternary composites was conducted. Bi-functional promising catalysts were employed for simultaneous Cr (VI) reduction and phenol oxidation as well as hydrogen evolution reaction (HER) through electro catalysis. Both Ag and Ce indicated their effects on orthorhombic WO3. Morphological studies showed big sheets of WO3 were ruptured by foreign materials. C − Ce − W and C − Ag − W surface linkages were analyzed by FTIR and Raman studies. DRS studies indicated that Ce into WO3 alters electronic configuration of WO3. GO/Ag-WO3 showed long absorption tail in visible region. The remarkable quenching of PL intensities is detected in GO/Ag-WO3. GO/Ag-WO3 comparatively produced small onset potential ∼ −175 mV, high current density of ∼75 mAcm−2, small Tafel slop ∼ 46 mV/dec and low charge-transfer resistance (Rct) ∼ 54 Ω. In HER, electronic interaction is strong driving force between WO3 and Ag while GO controls distribution of Ag on WO3/GO leading to fast conduction of charge transfer to improve HER activity. GO/Ag-WO3 composite exhibited elevated photo reduction of Cr (VI) (∼ 86.0 %) and oxidation of phenol (∼ 80.0 %). Trapping test indicated that O2•― and OH• is significant factor for degradation. It provides opportunities of environmentally friendly materials for multipurpose catalytic applications.

Effect of nickel and selenium co-doping on molybdenum disulfide structure and its electrochemical activity in polysulfide electrolyte

The development of a low-cost, and highly effective platinum (Pt)-free counter electrode (CE) that is highly stable towards polysulfide electrolyte presents a substantial challenge. Trigonal Molybdenum disulfide (1T-MoS2) has shown good chemical stability toward polysulfide electrolytes. In this study, 1T-MoS2 was prepared by co-doping with nickel (Ni) and selenium (Se) into MoS2 through hydrothermal method and utilizing its reduction activity toward polysulfide electrolyte. According to electrochemical impedance spectroscopy (EIS) analysis, Ni-Se-MoS2 has a low charge transfer resistance and electron recombination lifetime. In addition, cyclic voltmeter (CV) analysis reveals a high absolute area indicating a high level of electrocatalytic activity for polysulfide reduction at the electrolyte/counter electrode (CE) interface. The XRD analysis shows that the phase shifting of 2H MoS2 to 1 T MoS2 and the intensity of the co-doped sample is lower than that of others. SEM analysis reveals a microsphere-flower-like morphology that increases specific surface area.

Electrodeposition of NiCo on stainless steel substrate using deep eutectic solvent for efficient hydrogen evolution and methanol oxidation reactions

The electrodeposition of NiCo on a stainless-steel substrate using Deep eutectic solvent (DES) was carried out using constant current methods. A 1:2 mol ratio of ChCl (Choline chloride) and crystalline urea was used to prepare DES. The XRD analysis of the fabricated NiCo@SS showed a highly crystalline nature, and the SEM image revealed the fabricated electrode surface morphology. The composition and oxidation state of the deposited material were confirmed by EDAX and XPS techniques. The prepared electrodes were subjected to LSV and CV studies with 1 M KOH using a three-electrode system to analyse its catalytic ability in the Hydrogen evolution reaction (HER) and methanol oxidation reaction (MOR). Among all the deposited electrocatalysts, NiCo@SS demonstrated the highest catalytic activity and excellent stability for the hydrogen evolution reaction (HER), achieving an overpotential of 257 mV at a current density of 100 mA/cm2. Additionally, NiCo@SS exhibited a remarkable current density of 240 mA at a potential of 0.8 V towards the MOR. The synthesized NiCo@SS possessed excellent low overpotential, low charge transfer resistance, high current density, and large surface area. The explored catalyst of NiCo@SS was examined with different concentrations of methanol using the CV technique. Finally, the stability of NiCo@SS, as examined by chronoamperometry and LSV with 3000 cycles, revealed it to be a robust, stable catalyst towards HER and OER.

Enhanced brackish water desalination in capacitive deionization with composite Zn-BTC MOF-incorporated electrodes

In this study, composite electrodes with metal–organic framework (MOF) for brackish water desalination via capacitive deionization (CDI) were developed. The electrodes contained activated carbon (AC), polyvinylidene fluoride (PVDF), and zinc-benzene tricarboxylic acid (Zn-BTC) MOF in varying proportions, improving their electrochemical performance. Among them, the E4 electrode with 6% Zn-BTC MOF exhibited the best performance in terms of CV and EIS analyses, with a specific capacity of 88 F g−1 and low ion charge transfer resistance of 4.9 Ω. The E4 electrode showed a 46.7% increase in specific capacitance compared to the E1 electrode, which did not include the MOF. Physicochemical analyses, including XRD, FTIR, FESEM, BET, EDS, elemental mapping, and contact angle measurements, verified the superior properties of the E4 electrode compared to E1, showcasing successful MOF synthesis, desirable pore size, elemental and particle-size distribution of materials, and the superior hydrophilicity enhancement. By evaluating salt removal capacity (SRC) in various setups using an initially 100.0 mg L−1 NaCl feed solution, the asymmetric arrangement of E1 and E4 electrodes outperformed symmetric arrangements, achieving a 21.1% increase in SRC to 6.3 mg g−1. This study demonstrates the potential of MOF-incorporated electrodes for efficient CDI desalination processes.

Nickel-based metal-organic-frameworks as electrocatalysts for electrochemical oxidation of ammonia

Electrochemical oxidation of ammonia can produce hydrogen by splitting the ammonia molecules, not merely facilitating the elimination of ammonia but also augmenting sustainable hydrogen-based technological systems. However, the anode reaction is sluggish and the development of novel electrocatalysts is the major method to overcome this demerit. Herein, three kinds of Ni-based MOFs (Ni-BDC, Ni-BTC, and Ni-NH2-BDC) were prepared and used as electrocatalysts towards electrochemical oxidation of ammonia for the first time. At optimized working condition (0.5 V), Ni-NH2-BDC presents the response current density of 2.12 mA/cm2 with the current efficiency of 92.6%, both of which are significantly higher than those of Ni-BDC and Ni-BTC, indicating the better performance of Ni-NH2-BDC. EIS tests and the measurement of conductivity revealed that the good performance of Ni-NH2-BDC could be attributed to the lower charge transfer resistance at the electrode/electrolyte interface and the significantly improved conductivity which is caused by the introduction of NH2 groups.This work shed lights on the development of MOFs electrocatalysts for ammonia oxidation as well as other electrochemical reactions.

Sensitive Electrochemical Sensor for Gallic Acid Determination in Honey Based on g-C3N4/AuNPs Modified Carbon Paste Electrode

Gallic acid (GA) is a well-known polyphenol that occurs naturally in plants and is used as a chemical marker or standard antioxidant in analytical research. Here, a carbon paste electrode was modified with a nanocomposite of graphitic carbon nitride and gold nanoparticles (g-C3N4/AuNPs/CPE). The g-C3N4/AuNPs was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. Electrochemical impedance spectroscopy, cyclic voltammetry, and differential pulse voltammetry methods were used to investigate the electrochemical behavior of GA on the electrode. EIS analysis exhibited lower charge-transfer resistance in g-C3N4/AuNPs/CPE than CPE; 250 vs 1500 Ω, respectively. The g-C3N4/AuNPs/CPE was used to GA sensing with limit of detection and linear response range of 0.025 and 0.16–4.10 μM, respectively via DPV. Then, the GA content in Iranian honey samples with different floral origins such as Ziziphus, Barberry, Thyme, Astragalus, Eucalyptus and Coriander was successfully determined. According to result, the fabricated electrochemical sensor could be useful for GA evaluation in food samples.

Evaluation of low-cost carbon/metal electrodes as cathodes and anodes in sediment microbial fuel cells

In the present study, influence of different anode and cathode materials including carbon felt, carbon cloth, and several metal electrodes with or without carbon cloth covering on sediment microbial fuel cell (SMFC) performance was investigated. Results suggested that stainless steel poorly performed as cathode electrode whereas it exhibited reasonable performance as anode. In SMFCs with carbon felt cathode, anodes including 400 series stainless steel mesh and 300 series stainless steel plate, both covered with carbon cloth, led to higher maximum power densities of 88 and 87 mW/m−2, respectively, compared with carbon felt, carbon cloth, 400 series stainless steel mesh, 300 series stainless steel mesh covered with carbon cloth, and copper plate covered with carbon cloth (power densities of 40, 74, 53, 68, and 47 mW/m−2, respectively). They also resulted in higher loss on ignition (LOI) removals of 9.4 % and 8.7 %, respectively. Cyclic voltammetry results showed that stainless steel plate covered with carbon cloth produced the highest redox current that was two times that of the carbon cloth. In addition, electrochemical impedance spectroscopy indicated lower charge transfer resistance in the SMFC with anodes including 400 series stainless steel mesh (20.6 Ω) and 300 series stainless steel plate (25.7 Ω), both covered with carbon cloth, compared to other anode materials. These findings suggest that stainless steel electrodes covered with carbon cloth provide SMFCs with improved electrochemical characteristics that enhance their electricity production and organic matter removal.

A highly efficient and self-supporting nanoporous FeMoC catalyst for enhanced hydrogen evolution reaction

Optimizing structure and surface morphologies in electrocatalyst design are important to enhance the intrinsic activity of the hydrogen evolution reaction (HER). Mo-based phosphides and carbides have been confirmed as the widely-reported catalysts for HER. However, the origin of their enhanced catalytic activity is not fully clarified. Herein, the np-FeMoC and np-FeMoP with a self-supporting nanoporous structure were prepared using the melt-spinning and dealloying methods. Benefiting from the self-supporting electrode, nanoporous structure, abundant active species, low charge-transfer resistance and electron synergy, the np-FeMoC exhibits good catalytic performance. The np-FeMoC performs a low overpotential of 50.8 mV at 10 mA cm−2 current density for HER in 1 M KOH. This value is 2.7 times lower than that of the np-FeMoP sample, indicating a synergistic effect between Mo2C and Fe. From XPS and in-situ Raman results, it was observed that the dissolution of Mo2C occurs accompanied by dynamic evolution during the HER process on the np-FeMoC surface. This work unveils the intrinsic activity of Mo-based carbide and phosphide, providing valuable guidance for reasonable exploit of high-performance HER catalysts.

Water-soluble biowaste gum binders for natural graphite anode for lithium-ion batteries

Anode materials for lithium-ion batteries (LIBs) are crucial, as lithium insertion takes place in the anode during the charging process. Also, it is rational to replace the conventional polyvinylidene fluoride (PVdF) with a water-soluble binder because the former employs N-Methyl-2-pyrrolidone, which is environmentally harmful. To address the problem, we fabricated natural graphite (NG)-based anodes with water-soluble biowaste (W-SB) binders from the gum of the tree Cochlospermum gossypium and PVdF. Both of the electrodes were fabricated using 10 wt% of binder and were evaluated for their electrochemical performance. The NG-W-SB electrode showed good mechanical properties and maintained structural integrity after cycling, this promoted low charge transfer resistance on the electrode. NG-W-SB-based electrode showed high current peaks in the 1st cycle being an indication of enhanced electrochemical performance, unlike the NG-PVdF electrode which showed slightly low peaks. NG-W-SB maintained a higher stable capacity retention up to 360 cycles, whereas NG-PVdF had a capacity degradation after 200 cycles indicating a low capacity retention until the end of the cycle. Generally, W-SB binders showed highly enhanced cycling retention characteristics, comparable rate capabilities, and lower electrode resistance, which opened a new avenue for adopting biowaste (gum) as a functional water-soluble binder for LIBs applications.

Versailles Santa Barbara-5 derived bifunctional one-dimensional electrocatalysts of hierarchical Ni3S2 nanoprism@nanosheets arrays for self-supporting and binder-free efficient supercapacitor and methanol oxidation reaction

We herein present a structure consisting of two-dimensional (2D) single-crystal Ni3S2 nanosheets designed on one-dimensional (1D) Ni3S2 nanoprism arrays (also known as Ni3S2 nanoprism@nanosheets). These arrays are directly synthesized over nickel foam, which is referred to as Ni3S2/NF. These structures can be used as binderless, self-supporting electrodes for bifunctional methanol oxidation reaction (MOR) applications and high energy density hybrid supercapacitors (HSC). Ni3S2/NF is synthesized through the two steps of hydrothermal processes. In step I, 1D hexagonal Versailles Santa Barbara-5 (VSB-5) nanorod arrays have been prepared onto the surface of NF (denoted as VSB-5/NF). The precursor for step II was 1D VSB-5 nanorod arrays, which were transformed into Ni3S2 using Na2S as a sulfur source via the Kirkendall effect. Electrochemical examination results show that as-synthesized Ni3S2/NF electrode exhibited a high specific capacitance (Cs) of 145.0 mA h g−1 at 5 A g−1, low series resistance (0.18 Ω) and charge-transfer resistance (0.05 Ω), small relaxation time constant (τ0 = 8 ms) and high frequency response at 125.8 Hz. Ni3S2/NF has a superior specific capacity of 145.0 mA h g−1 at 5 A g−1 as a SC electrode. The Ni3S2/NF//CNTs/NF HSC can be operated up to 1.6 V in a 3 M KOH electrolyte, delivering an impressive energy density of 256.35 W h kg−1 at a power density of 6400 W kg−1. The as-assembled Ni3S2/NF//CNTs/NF HSC device exhibited an impressive stability of 81 % even after undergoing 10,000 charge-discharge cycles. When compared to previously reported catalysts, Ni3S2/NF was proved to be an excellent electrocatalyst for MOR due to its ability to generate a current density of 215.0 mA cm−2 at 0.5 VSCE, while maintaining a superior and stable current density of 619.2 mA cm−2 at 0.8 VSCE.

Facile and fast fabrication of CuCo alloy and N-codoped hierarchical porous carbon catalyst for efficient oxygen reduction reaction in microbial fuel cells

Designing a low-cost, high-performance oxygen reduction reaction (ORR) catalyst to replace the precious metal catalyst remains a huge challenge for microbial fuel cells (MFCs). Herein, a facile and rapid approach to fabricate highly active N-doped hierarchical porous carbon (NHPC) supported bimetal CuCo/NHPC composites with densely accessible active sites is developed by pyrolysis of Cu-doped ZIF-67 (CuCo-ZIF) precursor. In which, CuCo-ZIF precursor is synthesized through a one-pot hydrothermal method. Results showed that in addition to create additional Cu-Nx sites and increase N content, the Cu doping induces a hierarchical porous structure CuCo/NHPC composite with pores centered around 2.4, 4.2 nm and 10–60 nm, which can significantly accelerate the mass/electron transfer and improve efficient utilization of the active sites. The resulting CuCo/NHPC composite provides abundant active sites, high content of pyridinic-N and graphitic-N, which significantly boosts ORR performances. The CuCo/NHPC-T with pyrolysis temperature of 800 °C achieves remarkable ORR activity with low charge transfer resistances, high half-wave potential. The MFC assembled with CuCo/NHPC-800 (774.2 mW·m−2 and 0.713 V) significantly outperforms MFC assembled with Co-NC-800 (541.9 mW·m−2 and 0.583 V) in terms of maximum power density and open-circuit voltage. Moreover, the output voltage of MFC assembled with CuCo/NHPC-800 exhibited no significant downward trend within 30 days, which was better than that of Pt/C catalyst. This work provides a feasible time-saving route to develop promising nitrogen-enriched mesoporous carbon bimetallic ORR catalysts.

Manganese-enriched prussian blue nanohybrids with smaller electrode potential and lower charge transfer resistance to enhance combination therapy

Prussian blue (PB) is authenticated in clinical treatment, while it generally exhibits unfavorable chemodynamic therapy (CDT) performance. Herein, we developed manganese-doped prussian blue (PBM) nanoparticles to significantly enhance both CDT and photothermal therapy (PTT) effect. The lower redox potential of Mn3+/2+ (0.088 V) in PBM against that of Fe2+/3+ (0.192 V) in PB leads to favorable electron transfer of PBM with respect to PB. Besides, PBM has a lower charge-transfer resistance (Rct) of 2.98 Ω than 4.83 Ω of PB. Once PBM entering the tumor microenvironment (TME), Mn3+ may be readily reduced by glutathione (GSH) and therein to enhance intracellular oxidative stress. Meanwhile, the superoxide dismutase (SOD)-like activity of PBM facilitates the conversion of endogenous superoxide (O2•−) into H2O2. Mn2+ subsequently catalyzes H2O2 to generate toxic hydroxyl radicals (•OH). Notably, the PBM plus laser irradiation can effectively trigger a robust immunogenic cell death (ICD) due to the combination therapy of CDT and PTT. Additionally, the mice treated by PBM followed by laser irradiation efficiently avoided splenomegaly and lung metastasis, along with significant up-regulation of the Stimulator of Interferon Genes (STING) expression. Overall, PBM significantly inhibits tumor growth and metastasis, making it a promising multifunctional nanoplatform for cancer treatment.

Unravelling the efficacy of pencil graphite anode decorated with PdCu@γ-Fe2O3 nanoparticles in the electro-oxidation of amoxicillin: Insights into kinetics, oxidative pathways and toxicity evaluation

Indiscriminate use of antibiotics has resulted in the occurrence of antibiotic residues in sediments, water bodies and industrial sewage, causing ill effects on aquatic organisms and humans. Electrochemical oxidation process via in-situ generation of strong oxidant •OH is the promising method for the removal of pollutants. In this work, PdCu/γ-Fe2O3 NPs electrodeposited pencil graphite electrode (PdCu/γ-Fe2O3@PGE) has been projected as a cost-effective anode for electro-oxidation of amoxicillin (AMX), while bare PGE was used as a cathode to generate H2O2. The electrochemical measurements showed that PdCu/γ-Fe2O3 @PGE exhibited lower ΔEp (0.191 V), high electrochemical active surface area (ECSA) (0.4620 cm2), higher oxygen evolution potential (OEP) (1.72 V), and lower charge transfer resistance of 9.747 Ω/ cm2 which was ideal for electro-oxidation of AMX. Under the optimum reaction conditions (I = 0.2 mA, pH = 4), the % AMX removal reached 90.5 % after 50 min of electro-oxidation in 0.5 M NaCl. •OH, H2O2, and HOCl were found to be the in-situ generated oxidants. The AMX solution after electro-oxidation did not exhibit antibacterial activity. The toxicity of the formed intermediates were evaluated using Toxicity Estimation Software Tool (T.E.S.T) and found to be less toxic. The electrical energy consumption was estimated to be 0.786 kWhm−3.Thus, modified PGE finds application in the remediation of effluents containing amoxicillin.

In-situ growth transformation and oxygen vacancy synergistic modulation of the electronic structure of NiCo-LDH enables high-performance hybrid supercapacitors

This article successfully constructs NiCo-LDH nano cages formed by in-situ triggering (IS-LDH), and synergistically modulates the electronic structure by introducing oxygen vacancies. The in-situ triggered generation of NiCo-LDH (IS-LDH) by synthesizing ZIF-67 owns a typical rhombic dodecahedral structure and sensitivity to acid etching. Characterization analysis revealed that the IS-LDH nanocage succeeded the polyhedral structure morphology of ZIF-67 but with multiple vertically aligned nanosheets on the shell. Oxygen vacancies (Ov) were introduced into the IS-LDH through a chemical reduction process using sodium borohydride. The findings demonstrate that the synthesized OvIS-LDH nanocapacitor has a low charge transfer resistance (Rct) with a specific capacitance as high as 1111C g−1 (at 1 A g−1). After 10,000 cycles of charge-discharge measurements, the capacity retention rate was 89.45%. Density functional theory (DFT) calculations confirmed that the inclusion of Ov enhanced the repulsion of OH− by the LDH nanosheets and improved the intrinsic conductivity of LDH. The assembled hybrid supercapacitor (OvIS-LDH//AC) successfully powered an LED light for 20 min. This study proposes a logical approach for developing anode materials that can enhance the performance of supercapacitors.

High Entropy Spinel Oxide (AlCrCoNiFe2)O as Highly Active Oxygen Evolution Reaction Catalysts.

The advancement of water electrolyzer technologies and the production of sustainable hydrogen fuel heavily rely on the development of efficient and cost-effective electrocatalysts for the oxygen evolution reaction (OER). High entropy ceramics, characterized by their unique properties, such as lattice distortion and high configurational entropy, hold significant promise for catalytic applications. In this study, we utilized the sol-gel autocombustion method to synthesize high entropy ceramics containing a combination of 3d transition metals and aluminum ((AlCrCoNiFe2)O). We then compared their electrocatalytic performance with other series of synthesized multimetal and monometallic oxides for the OER under alkaline conditions. Our electrochemical analysis revealed that the high entropy ceramics exhibited excellent performance and the lowest charge transfer resistance, Tafel slope (29 mV·dec-1), and overpotential (η10 = 230 mV). These remarkable results can be primarily attributed to the high entropy effect induced by the addition of Al, Cr, Co, Ni, and Fe, which introduces increased disorder and complexity into the material's structure. This, in turn, facilitates more efficient OER catalysis by providing diverse active sites and promoting optimal electronic configurations for the reaction. Furthermore, the strong electronic interactions among the constituent elements in the metallic spinels further enhance their catalytic activity in the initiation of the OER process. Combined with the reduced charge transfer resistance, these factors collectively play pivotal roles in enhancing the OER performance of the electrocatalysts. Overall, our study provides valuable insights into the design and development of high-performance electrocatalysts for sustainable energy applications. By harnessing the high entropy effect and leveraging strong electronic interactions, electrocatalytic materials can be tailored to improve efficiency and stability, thus advancing the progress of clean energy technologies.

Iron-Cobalt Nanoparticles Embedded in B,N-Doped Chitosan-Derived Porous Carbon Aerogel for Overall Water Splitting.

Given their intriguing properties, porous carbons have surfaced as promising electrocatalysts for various energy conversion reactions. This study presents a unique approach where iron-cobalt (FeCo) is confined in a boron, nitrogen-doped chitosan-derived porous carbon aerogel (BNPC-FeCo) to serve as an electrocatalyst for the hydrogen evolution and oxygen evolution reactions (HER and OER). The BNPC-FeCo-900 electrocatalyst demonstrates excellent catalyst activity, with very low overpotentials of 186 and 320 mV at 10 mA cm-2, low Tafel slopes of 82 and 55 mV dec-1, and low charge transfer resistance of 2.68 and 9.25 Ω for HER and OER, respectively. Density functional theory (DFT) calculations further reveal that the cooperation between the boron, nitrogen codoped porous carbon, and the FeCo nanoparticles reduces intermediates' energy barriers, significantly enhancing the HER and OER performance. In conclusion, this work offers significant and informative perspectives into the potential of porous carbon materials as dual-purpose electrocatalysts for water splitting.

Sewage sludge-derived biocarbons as catalysts of bioanodes in a dual-chamber microbial fuel cell using nejayote as substrate

In this work, nejayote (wastewater from tortilla industry) was evaluated as substrate of a dual-chamber microbial fuel cell (MFC). For this purpose, novel bioanodes were built using Bacillus subtilis (B. subtilis) as the electrochemically active microorganism (EAM), and sewage sludge-derived biocarbon (SSB) and methanol-functionalized SSB (FSSB) as catalysts. The relationship between the physicochemical properties of SSB and FSSB, biocompatibility, electrochemical performance and the percentage of COD removed was analyzed. Up to 70% of chemical oxygen demand (COD) from nejayote was successfully removed using the SSB + B. subtilis bioanode, with the advantage of energy generation by the MFC (Pcell= 1.44 mW m-2 and jcell= 41 mA m-2). An adverse effect was observed when functionalizing SSB to produce FSSB. Despite a fair biocompatibility, the FSSB + B. subtilis bioanode promoted fermentation reactions that increased the COD and charge transfer resistance. The improved performance of SSB + B. subtilis was ascribed to a reasonable biocompatibility, low charge transfer resistance and less limitation to the diffusion of proton species between the biofilm and the substrate. Therefore, the treatment of nejayote in a MFC with the SSB + B. subtilis bioanode was identified as a promising alternative for decreasing COD and generating small amounts of energy, instead of using energy for its remedy.