Efficient Oxygen Reduction Research Articles

CoNi-N/P-Doped Carbon Nanotubes as Catalysts for Efficient Oxygen Reduction Reaction.

Transition metals (TMs) supported by heteroatom-doped carbon materials are considered to be the potential alternatives to the Pt/C catalyst owing to their low cost, outstanding electrocatalytic efficiency, and excellent electrochemical durability. In this paper, N/P-doped carbon nanotube (CNT) (N/P-CNT)-supported monometallic (Co, Ni) and bimetallic (CoNi) catalysts were synthesized by one-step pyrolysis using diammonium hydrogen phosphate, 2-methylimidazole and organometallic salts as precursors, and the CNT as the catalyst carrier; the effects of transition TM types and pyrolysis temperature (Tp) on the microstructure and electrochemical properties were explored. The analysis exhibited that the CoNi bimetallic catalyst was superior to both Co and Ni monometallic catalysts, and the catalysts pyrolyzed at 900 °C exhibited a better graphitization degree. The optimal CoNi-N/P-CNT-900 displayed remarkable oxygen reduction reaction electrocatalytic performance with a half-wave potential (E1/2) of 0.86 V and excellent methanol tolerance and stability. Moreover, the Zn-air battery coated with CoNi-N/P-CNT-900 demonstrated a larger open circuit voltage of 1.577 V, a larger peak power density of 212.89 mW cm-2 at 357.8 mA cm-2, as well as a higher specific capacity of 799 mA h gZn-1, superior to that of the Pt/C catalyst (1.492 V, 96.04 mW cm-2 at 216.8 mA cm-2, 735 mA h gZn-1), showing outstanding practical value. This study is expected to promote the commercialization of the electrocatalysts.

Janus structural TaON/Graphene-like carbon dual-supported Pt electrocatalyst enables efficient oxygen reduction reaction

Developing carbon-supported Pt-based electrocatalysts with high activity and long-durability for the oxygen reduction reaction (ORR) is an enormous challenge for their commercial applications due to the corrosion of carbon supports in acid/alkaline solution at high potential. In this work, a Janus structural TaON/graphene-like carbon (GLC) was synthesized via an in-situ molecular selfassembly strategy, which was used as a dual-carrier for platinum (Pt). The as-obtained Pt/TaON/GLC presents high half-wave potential (0.94 V vs. RHE), excellent mass (1.48 A mgPt-1) and specific (1.75 mA cmPt-2) activities at 0.9 V, and superior long-term durability with a minimal loss (8.0 %) of mass activity after 10,000 cycles in alkaline solution, outperforming those of Pt/C and other catalysts. The structural characterizations and density functional theory (DFT) calculations indicate that the Pt/TaON/GLC catalyst exhibits the maximum synergies, including enhanced interfacial electron density, improved charge transfer, enhanced O2 adsorption, andsuperimposed OO cleavage. This work shows a potential strategy for preparing the high-active and long-durable Pt-based electrocatalyst by synergism-promoted interface engineering.

Hierarchically porous Fe-N-C microspheres via pyrolyzing hypercrosslinked polypyrrole synthesized by Fe3+-catalysis for efficient oxygen reduction in Zn-air battery

Fe-N-C catalysts have developed into the most promising substitute for Pt-based precious metal catalysts toward cathodic oxygen reduction reaction (ORR) of fuel cells and Zn-air batteries. Hypercrosslinked polypyrrole microspheres coordinated with Fe (HCP-Py-Fe) were first prepared by condensation of pyrrole (Py) and dimethoxymethane (FDA) in the presence of FeCl3 as both catalyst and Fe source, and then thermally activated with KOH during pyrolysis followed by acid leaching and heat-treatment, thus constructing hierarchically porous Fe-N-C microspheres (denoted as PPy/FDA-Fey-HT2-x). The morphology and structural properties of the final synthesized PPy/FDA-Fey-HT2-x could be tailored to a certain extent by controlling the adding quantities of KOH (x) in the initial solid mixture before pyrolysis and FeCl3 (y) during condensation of Py and FDA. As a result, the PPy/FDA-Fe0.4-HT2–0.25 demonstrated the highest half-wave potential of 0.87 V vs. RHE, with a desired 4-electron transfer for ORR in alkaline medium, which is attributed to the hierarchically micro/mesoporous structure, high surface area and extremely low content of magnetic iron species. Remarkable methanol resistance and durability with only a loss of ∼4 mV in half-wave potential after 10000 potential cycles were obtained as well. The aqueous Zn-air battery (ZAB) fabricated with the PPy/FDA-Fe0.4-HT2–0.25 as cathode catalyst delivered a comparable discharge performance to that of the Pt/C-based ZAB but far superior cycling stability. This facile route is promising for large-scale production of Fe-N-C materials as cathodic electrocatalyst applied in practical energy conversion devices.

CuFe nanoparticles coupled Cu–Nx for enhancing oxygen reduction reaction

For the large-scale development of zinc-air batteries (ZABs), designing efficient, and cost-effective oxygen reduction reaction (ORR) electrocatalysts is crucial yet challenging. Herein, CuFe nanoparticles coupled with Cu–Nx active sites co-anchored on 2D nitrogen–doped porous carbon nanosheets (CuFe@Cu–N–C) were obtained by the pyrolysis of Cu–MOF–74, nitrogen source, and ferric salt. The 2D porous carbon structure and the coupling effect between CuFe nanoparticles and Cu–Nx active sites endowed the CuFe@Cu–N–C electrocatalyst with excellent ORR electrocatalytic performance. Consequently, the CuFe@Cu–N–C electrocatalyst exhibited enhanced ORR activity with a higher half–wave potential than Cu–N–C, surpassing even that of the commercial 20 % Pt/C by 21 mV in alkaline media. Additionally, the CuFe@Cu–N–C electrocatalyst exhibited superior ORR stability to commercial 20 % Pt/C. Primary ZABs assembled with the CuFe@Cu–N–C as the cathode ORR electrocatalyst also showed excellent electrochemical properties. The work shows that the prepared CuFe@Cu–N–C electrocatalyst can serve as an ideal alternative to Pt-based catalysts for ZABs.

Integrating Multipolar Structures and Carboxyl Groups in sp2‐Carbon Conjugated Covalent Organic Frameworks for Overall Photocatalytic Hydrogen Peroxide Production

The direct production of hydrogen peroxide (H2O2) through photocatalytic reaction via H2O and O2 is considered as an ideal approach. However, the efficiency of H2O2 generation is generally limited by insufficient charge and mass transfer. Covalent organic framework (COFs) offer a promising platform as metal‐free photocatalyst for H2O2 production due to their potential for rational design at the molecular level. Herein, we integrated the multipolar structures and carboxyl groups into COFs to enhance the efficiency of photocatalytic H2O2 production in pure water without any sacrificial agents. The introduction of octupolar and quadrupolar structures, along with an increase of molecular planarity, created efficient oxygen reduction reaction (ORR) sites. Meanwhile, carboxyl groups could not only boost O2 and H2O2 movement via enhancement of pore hydrophilicity, but also promote proton conduction, enabling the conversion to H2O2 from ·O2‐, which is the crucial intermediate product in H2O2 photocatalysis. Overall, we demonstrate that TACOF‐1‐COOH, consisting of optimal octupolar and quadrupolar structures, along with enrichment sites (carboxyl groups), exhibited a H2O2 yield rate of 3542 μmol h‐1 g‐1 and a solar‐to‐chemical (SCC) efficiency of 0.55%. This work provides valuable insights for designing metal‐free photocatalysts for efficient H2O2 production.

Integrating Multipolar Structures and Carboxyl Groups in sp2-Carbon Conjugated Covalent Organic Frameworks for Overall Photocatalytic Hydrogen Peroxide Production.

The direct production of hydrogen peroxide (H2O2) through photocatalytic reaction via H2O and O2 is considered as an ideal approach. However, the efficiency of H2O2 generation is generally limited by insufficient charge and mass transfer. Covalent organic framework (COFs) offer a promising platform as metal-free photocatalyst for H2O2 production due to their potential for rational design at the molecular level. Herein, we integrated the multipolar structures and carboxyl groups into COFs to enhance the efficiency of photocatalytic H2O2 production in pure water without any sacrificial agents. The introduction of octupolar and quadrupolar structures, along with an increase of molecular planarity, created efficient oxygen reduction reaction (ORR) sites. Meanwhile, carboxyl groups could not only boost O2 and H2O2 movement via enhancement of pore hydrophilicity, but also promote proton conduction, enabling the conversion to H2O2 from ⋅O2 -, which is the crucial intermediate product in H2O2 photocatalysis. Overall, we demonstrate that TACOF-1-COOH, consisting of optimal octupolar and quadrupolar structures, along with enrichment sites (carboxyl groups), exhibited a H2O2 yield rate of 3542 μmol h- 1 g-1 and a solar-to-chemical (SCC) efficiency of 0.55 %. This work provides valuable insights for designing metal-free photocatalysts for efficient H2O2 production.

Prussian Blue Analogues Derived Bimetallic CoNi@NC as Efficient Oxygen Reduction Reaction Catalyst for Mg‐Air Batteries

The magnesium‐air (Mg‐air) batteries are regarded as a highly promising system for electrochemical energy conversion and storage, owing to exceptional energy density, notable safety and eco‐friendliness. The development of high‐performance and durable non‐noble metal catalysts for the cathodic oxygen reduction reaction (ORR) is crucial for advancing the practical use of Mg‐air batteries. The synergistic interaction between different metals in bimetallic catalysts is an effective strategy for enhancing the activity and stability of the catalysts. Herein, various prussian blue analogues (PBA) were selected as precursors to synthesis the bimetallic CoNi@NC, monometallic Co@NC and Ni@NC catalysts due to tunable chemical compositions. Compared with Co@NC and Ni@NC, the bimetallic CoNi@NC pyrolyzed at 600°C (CoNi@NC‐600) exhibits outstanding ORR performances and stability in alkaline (0.1 M KOH) and neutral (3.5 wt% NaCl) electrolytes. Following 5000 CV cycles, the half‐wave potentials for CoNi@NC‐600 show only minor negative shifts of 8 and 7 mV, respectively. Meanwhile, the CoNi@NC‐600 possesses the similar ORR reaction mechanism and activity with Pt/C. The primary Mg‐air battery assembled with CoNi@NC‐600 displays better discharge performances than that of Co@NC and Ni@NC. This study lays the foundation for future investigations into the advancement of non‐precious bimetallic catalysts for ORR in Mg‐air batteries.

Highly dispersed Co nanoparticles confined by mesopore-rich N-doped hollow carbon nanotubes for efficient oxygen reduction reaction and Zn-air battery

Oxygen reduction reaction (ORR) is an important reaction process in Zn-air batteries, and the catalyst plays a crucial role as the cathode in the system. However, the reported catalysts often exhibit poor durability and stability in the operation of air batteries. Here, we used g-C3N4 as a precursor to mix Co nanoparticles for carbonization, and synthesized a large number of carbon nanotubes (CNTs) interwoven cluster catalysts, namely Co/CNT-800. The obtained catalyst has a rolling grass like morphology, forming a highly conductive network, which helps to improve the electron transfer ability in the ORR process. At the same time, the influence of materials at different carbonization temperatures on the ORR of Zn-air batteries was studied. In alkaline media, Co/CNT-800 showed the high ORR performance, with a half-wave potential of 0.839 V (vs. RHE, Pt/C 0.845 V). After 5000 cycles, the E1/2 of the Co/CNT-800 catalyst only decreased by 9 mV, and its performance in stability tests and methanol tolerance tests was superior to Pt/C. When Co/CNT-800 catalyst is used as the air cathode for Zn-air batteries, it exhibits an excellent specific capacity of 709.2 mAh/g and a power density of 142.2 mW cm−2.This research achievement provides valuable insights for the development of high-performance Zn-air batteries and innovative guidance for the design of ORR catalysts.

A new highly active and CO2-stable heterostructure cathode material for solid oxide fuel cells developed from bismuth ion-modified cation-deficient Nd0.9BaCo2O5+δ

Efficient oxygen reduction kinetics as well as excellent stability are the main goals of current electrode materials for solid oxide fuel cells (SOFCs). Here, we present the latest findings regarding the augmentation of performance in SOFC through utilization of a novel heterogeneous cathode, consisting of an excess cation-deficient double perovskite Nd0.9BaCo2O5+δ (NBC90) backbone and in situ exsolved BaCo1-yBiyO3-x nanoparticles modified by bismuth (NBC90+B). The anisotropic growth of such self-assembled nanoparticles and the formation of multiple heterointerfaces exhibit an extremely strong activation effect. The in situ formed BaCo1-yBiyO3-x nanoparticles and cation-deficient NBC90 parental perovskite significantly enhance the catalytic activity and durability of the cathode toward oxygen reduction. The structural stability and CO2 tolerance of the cathode are greatly enhanced, which is attributed to the penetration of the high acidic Bi ions in the separated phase and the synergistic effect of the two-phase interface. The results unequivocally demonstrate the exceptional stability and efficiency of the NBC90+B composite as a promising cathode candidate for SOFCs.

Modulating the Bader Charge Transfer in Single p-Block Atoms Doped Pd Metallene for Enhanced Oxygen Reduction Electrocatalysis.

Metallene is considered as an emerging family of electrocatalysts due to its atomically layered structure and unique surface stress. Here we propose a strategy to modulate the Bader charge transfer (BCT) between Pd surface and oxygenated intermediates via p-d electronic interaction by introducing single-atom p-block metal (M=In, Sn, Pb, Bi) into Pd metallene nanosheets towards efficient oxygen reduction reaction (ORR). X-ray absorption and photoelectron spectroscopy suggests that doping p-block metals could facilitate electron transfer to Pd sites and thus downshift the d-band center of Pd and weaken the adsorption energy of O intermediates. Among them, the developed Bi-Pd metallene shows extraordinarily high ORR mass activity of 11.34 A mgPd -1 and 0.86 A mgPd -1 at 0.9 V and 0.95 V in alkaline solution, respectively, representing the best Pd-based ORR electrocatalysts ever reported. In the cathode of a Zinc-air battery, Bi-Pd metallene could achieve an open-circuit voltage of 1.546 V and keep stable for 760 h at 10 mA cm-2. Theoretical calculations suggest that the BCT between Pd surface and *OO intermediates greatly affects the bond length between them (dPd-*OO) and Bi doping could appropriately reduce the amount of BCT and stretch the dPd-*OO, thus enhancing the ORR activity.

Asymmetric cobalt porphyrins for pH-universal oxygen reduction reactions: Benzoic acid advances phenyl as substituents

Asymmetric metalloporphyrins are potential electrocatalysts to construct composites for efficient oxygen reduction reactions (ORRs) due to their inherent large dipole moment, which facilitates the charge separation. To find more effective molecular structures towards the ORRs, in particular their performance and electrolyte relationship, we rationally designed two A3B-type asymmetric cobalt porphyrin aPh-TCoP and aBA-TCoP with phenyl and benzoic acid as substituents, respectively. The ORR performance of the porphyrin-decorated carbon black composites was examined in five electrolytes at different pH values spanning from 0.7 to 13.7. It was found that aBA-TCoP/C exhibited better ORR activity and selectivity than aPh-TCoP/C in all solutions. Interestingly, both composites demonstrated their highest ORR activity in the pH13.7 electrolyte and exhibited 4-electron selectivity in the pH3.7 solution. This conclusion is drawn from a comprehensive analysis of various electrochemical properties, encompassing current density, reduction potentials, electron transfer numbers, and intermediate yields. The results illustrate the regulation of ORR properties by altering the electrolyte pH and a notable improvement in the ORR performance through the modification of porphyrin substituents. These findings offer a foundational understanding for the design of efficient metalloporphyrins and the attainment of controlled oxygen reduction in electrochemical devices.

Engineering both intrinsic characteristic and local microenvironment of platinum sites toward highly efficient oxygen reduction reaction

The optimization of the adsorption of oxygen-containing intermediates on platinum (Pt) sites of Pt-based electrocatalysts is crucial for the oxygen reduction reaction process. Currently, a large amount of researches mainly focus on modifying the bulk structure of the electrocatalysts, however, the vital role of solvent effect on the phase interfaces is often overlooked. Here, we successfully developed an electrocatalyst in which the ordered PtCo alloy anchors on the cobalt (Co) single-atoms/clusters decorated support (Co1,nNC) and its surface is further optimized using hydrophobic ionic liquid (IL). Experimental studies and theoretical calculations indicate that compressive stress on Pt lattice contributed by intrinsic structure and the local hydrophobicity caused by IL on the surface can suppress the stabilization of *OH on Pt. This synergistic effect affords outstanding catalytic performance, exhibiting a half-wave potential (E1/2) of 0.916 V vs. RHE and a mass activity (MA) of 1350.3 mA mgPt−1 in 0.1 mol/L perchloric acid (0.1 M HClO4) electrolyte, much better than the commercial Pt/C (0.849 V vs. RHE and 145.5 mA mgPt−1 for E1/2 and MA, respectively). Moreover, the E1/2 of IL-PtCo/Co1,nNC only lost 5 mV after 10,000 cyclic voltammetry (CV) cycles due to a strong and synergistic contact of the intermetallic PtCo alloy with the Co1,nNC support and IL. This research provides an effective method for designing efficient electrocatalysts by combining intrinsic structure and surface modification.

Effect of Carbon Support on the Properties of Fe, N, S Co-Doped ORR Catalysts Prepared by Molten Salt Method

In recent years, the development of sustainable and environmentally friendly catalysts for various electrochemical processes has become a major focus in the fields of energy storage and fine chemicals. Efficient and cost-effective oxygen reduction reaction (ORR) catalysts are crucial for the advancement of fuel cells and metal-air batteries. This study explores the use of rice husk-based porous carbon (RHPC) with a hierarchically porous structure as a support material for sustainable ORR catalysts. The performance of RHPC was compared with other commercial carbon materials, such as acetylene black (AB) and coconut shell carbon (YP-50), evaluating key properties including particle size, specific surface area, oxygen-containing functional groups, degree of graphitization, and hydrophilicity/hydrophobicity. Compared to AB, which has higher conductivity, and YP-50, which has a greater abundance of oxygen functional groups, RHPC demonstrated significant advantages as a catalyst support. The resulting Fe-NS/RHPC catalyst exhibited high activity (E1/2 = 0.858 V vs RHE, J = 4.83 mA cm−2), outperforming the standard Pt/C (E1/2 = 0.844 V vs RHE, J = 4.99 mA cm−2). When tested in a liquid Zn-air battery, the Fe-NS/RHPC catalyst achieved a peak power density of 116.2 mW cm−2 and a capacity of up to 792.5 mAh g−1.

Synergistically improving the performance of spinel cathode for efficient oxygen reduction electrocatalyst

Optimizing the performance of ceramic fuel cells requires the creation of effective and inexpensive electrocatalysts for the oxygen reduction process. Here, we detail a plan for converting the inert spinel CoAl2O4 into a highly active and superior material for low-temperature ceramic fuel cells through Fe substitution. It turns out that the iron substitution aids in surface reconstruction, increasing oxidation-reduction reaction (ORR) activity. In addition, the reduction in energy bandgap due to Fe doping enhance the Cathode ORR performance, which may be triggered by the ions' kinetics at the surface and interface. The surface layer and Fe doping considerably aid the oxidation-reduction reaction, which creates more oxygen vacancies at the active oxygen site. The prepared materials exhibit enhanced fuel cell performance of 542 mW/cm2 at a temperature of 520 °C. Remarkably, the prepared cathode exhibits a commendable performance of 200 mW/cm2 at a temperature of 420 °C.Furthermore, the CoFe1Al1O4 cell exhibits a decreased Rp (polarization resistance) value of 0.6423 ohm-cm2 at a temperature of 520 °C, demonstrating rapid ORR kinetics. The distribution relaxation time (DRT) shows that the Cathode oxidation-reduction reaction (ORR) activity increased with Fe doping. We present a promising method for improving the oxidation-reduction reaction efficiency of low-temperature ceramic fuel cells.

Porphyrin-enhanced microbial fuel cell with PCN-600 electrocatalyst for efficient oxygen reduction reaction and eco-friendly energy generation

Microbial fuel cells (MFCs) stand as a sustainable alternative for wastewater treatment and the production of clean energy. The effectiveness of this technology is intricately linked to the cathodic oxygen reduction reaction (ORR). The exceptional tunability of metal–organic frameworks (MOFs) offers a distinctive platform for customizing their inherent properties, making them promising candidates as new electrocatalysts. In this study, metalloporphyrin MOF (PCN-600) with 1D channels and micro/mesoporous structure was prepared utilizing the preassembled [Fe3O(OOCCH3)6] building blocks. Electrochemical measurements demonstrated the superior ORR performance of PCN-600 compared to bare graphite electrodes, with higher onset and half-wave potentials and enhanced electron transfer rates. PCN-600 exhibited a remarkable 52.72 % improvement in power density (179.43 mW m−2) compared to the control group (MFC-Ctrl, 88.41 mW m−2). Additionally, the chemical oxygen demand (COD) removal efficiency was enhanced, with MFC-PCN-600 achieving 82.58 % COD removal compared to 59.87 % in MFC-Ctrl. The electron-withdrawing N and M−N structure of PCN-600 guarantees an outperforming ORR catalyst toward bioelectricity generation during MFCs performance.

Highly porous layered carbon nanocomposites from the self-assembly of a poly(amic acid) for efficient oxygen reduction reaction catalysis

Porous layered carbon nanomaterials play important role in the efficient loading of electroactive substances for high performance energy conversion techniques. Herein, an intramolecular cyclization induced self-assembly (ICISA) strategy is proposed to prepare three-dimensional highly porous layered carbon nanostructures (LCs) for efficient loading of various transition metal nanoparticles for oxygen reduction reaction (ORR) catalysis. The amphiphilic alternating copolymer poly(amic acid) (PAA) is synthesized by the stepwise polymerization of hydrazine hydrate and pyromellitic dianhydride. Upon heating above 160 °C, the intramolecular cyclization reaction occurs, leading to the formation of rigid, crystalline and non-soluble polyimide segments in the backbone, which induces the self-assembly of the polymer to form dumbbell-shaped assemblies with a high solid content of 15%. After pyrolysis in a nitrogen atmosphere, LCs are obtained. Cobalt (Co), iron (Fe) and FeCo nanoparticles can be efficiently loaded, noted as Co@LCs, Fe@LCs and FeCo@LCs, respectively. The ORR catalytic performance of the catalysts is evaluated to give half wave potentials of 0.791, 0.787 and 0.812 V, and limit current densities of 4.92, 4.73 and 4.71 mA cm−2 for Co@LCs, Fe@LCs and FeCo@LCs, respectively. Overall, we propose an ICISA strategy to facilely prepare three-dimensional carbon nanomaterials with highly porous layered structure for efficient ORR catalysis.

Mn-modified nitrogen-doped Pt-based electrocatalyst for efficient oxygen reduction in aluminum-air batteries

Mn-modified nitrogen-doped Pt-based electrocatalyst for efficient oxygen reduction in aluminum-air batteries

Boron carbon nitride as efficient oxygen reduction reaction support

The electrocatalytic oxygen reduction reaction (ORR) is crucial for energy conversion systems such as fuel cells and metal-air batteries. Boron carbon nitrogen (BCN) is a novel functional material with a high specific surface area, excellent corrosion resistance, and outstanding electrochemical stability. These properties make BCN an effective ORR catalyst and a promising support for metal catalysts. This study leveraged the strong interaction between BCN and metals to anchor platinum nanoparticles (Pt NPs) onto the BCN surface (Pt/BCN), significantly enhancing the durability of traditional Pt/C catalysts in ORR. The half-wave potential of Pt/BCN is 0.927 V, higher than Pt/XC-72R (0.857 V) and commercial Pt/C (0.879 V). Notably, after 10,000 durability test cycles, the mass activity (MA) of Pt/XC-72R and commercial Pt/C decreased by 67 % and 75 %, respectively. Even after 50,000 cycles, Pt/BCN exhibited only a 54 % decrease in MA. Experimental data and density functional theory calculations confirmed increased electron transfer from Pt to the BCN support, indicating a strong electronic metal-support interaction (EMSI) between Pt and BCN. This strong EMSI effectively anchored the Pt NPs, preventing migration and aggregation during the ORR process. Consequently, our research introduces a novel electrocatalyst support material with significant potential for ORR and broader applications.

Anodic degradation of salicylic acid and simultaneous bio-electricity recovery in microbial fuel cell using waste-banana-peels derived biochar-supported MIL-53(Fe)-metal-organic framework as cathode catalyst

This research was aimed to synthesize waste banana peel biochar (BC) supported MIL-53(Fe) metal–organic framework (MOF) (MIL-53(Fe)/BC) as an efficient cathode catalyst for application in a microbial fuel cell (MFC) for the treatment of salicylic acid (SA)-laden wastewater. This investigation marks the first application of such a catalyst in a MFC for SA degradation. The results revealed an increment in power density of MFC-MIL-53(Fe)/BC by 2.34-folds (142.2 ± 1.5 mW/m2) as compared to MFC-MIL-53(Fe) (60.6 ± 1.8 mW/m2). Removal of chemical oxygen demand in MFC-MIL-53(Fe)/BC (93.8 ± 2.2 %) was found to be comparable to MFC-Pt/C (94.6 ± 1.5 %). The MFC-MIL-53(Fe)/BC demonstrated a 91.5 ± 2.0 % biodegradation of SA. The power recovery per unit cost by MFC-MIL-53(Fe)/BC was found to be 380.21 mW/US$, which is significantly higher than MFC-Pt/C (6.08 mW/US$), indicating that MIL-53(Fe)/BC could be an affordable replacement to pricey Pt as cathode catalyst for efficient oxygen reduction reaction.

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.