Electrocatalysts For Zn Research Articles

Bifunctional electrocatalysts for Zn–air batteries

This review focuses on the latest advances related to the development of non-precious metal catalysts for the air electrode in Zn–air batteries (ZABs), which are promising devices to power energy grids and electric vehicles.

Spent alkaline battery-derived manganese oxides as efficient oxygen electrocatalysts for Zn–air batteries

The discharged cathode from depleted primary Zn–MnO2batteries can be recyclably utilized as efficient oxygen reduction/evolution electrocatalysts to build Zn–air batteries.

Iron-decorated nitrogen-rich carbons as efficient oxygen reduction electrocatalysts for Zn-air batteries.

A low-cost and scalable method has been developed to synthesize Fe-decorated N-rich carbon electrocatalysts for the oxygen reduction reaction (ORR) based on pyrolysis of metal carbonyls containing metal-organic frameworks (MOFs). Such a method simultaneously optimizes the Fe-related active sites and the porous structure of the catalysts. Accordingly, the best-performing Fe-NC-900-M catalyst shows excellent ORR activity with a half-wave potential of 0.91 V vs. RHE, exceeding that of the 40% Pt/C catalyst in alkaline media. Furthermore, the zinc-air batteries constructed with Fe-NC-900-M as the cathode catalyst exhibit high open-circuit voltage (1.5 V) and peak power density (271 mW cm-2), and outperform most zinc-air batteries with noble-metal free ORR catalysts.

Selective CO2 Reduction on Zinc Electrocatalyst: The Effect of Zinc Oxidation State Induced by Pretreatment Environment

Here, we have developed porous nanostructured Zn electrocatalysts for CO2 reduction reaction (CO2RR), fabricated by reducing electrodeposited ZnO (RE-Zn) to activate the CO2RR electrocatalytic performance. We discovered that the electrochemical activation environment using CO2-bubbled electrolyte during reducing ZnO in a pretreatment step is important for highly selective CO production over H2 production, while using Ar gas bubbling instead can lead to less CO product of the Zn-based catalyst in CO2RR later. The RE-Zn activated in CO2-bubbled electrolyte condition achieves a Faradaic efficiency of CO production (FECO) of 78.5%, which is about 10% higher than that of RE-Zn activated in Ar-bubbled electrolyte. The partial current density of CO product had more 10-fold increase with RE-Zn electrodes than that of bulk Zn foil at −0.95 V vs RHE in KHCO3. In addition, a very high FECO of 95.3% can be reached using the CO2-pretreated catalyst in KCl electrolyte. The higher amount of oxidized zinc states has been...

Electrocatalysts: MOF‐Based Metal‐Doping‐Induced Synthesis of Hierarchical Porous CuN/C Oxygen Reduction Electrocatalysts for Zn–Air Batteries (Small 30/2017)

Electrocatalysts: MOF‐Based Metal‐Doping‐Induced Synthesis of Hierarchical Porous CuN/C Oxygen Reduction Electrocatalysts for Zn–Air Batteries (Small 30/2017)

MOF-Based Metal-Doping-Induced Synthesis of Hierarchical Porous CuN/C Oxygen Reduction Electrocatalysts for Zn-Air Batteries.

A transition-metal-nitrogen/carbon (TM-N/C, TM = Fe, Co, Ni, etc.) system is a popular, nonprecious-metal oxygen reduction reaction (ORR) electrocatalyst for fuel cell and metal-air battery applications. However, there remains a lack of comprehensive understanding about the ORR electrocatalytic mechanism on these catalysts, especially the roles of different forms of metal species on electrocatalytic performance. Here, a novel CuN/C ORR electrocatalyst with a hybrid Cu coordination site is successfully fabricated with a simple but efficient metal-organic-framework-based, metal-doping-induced synthesis strategy. By directly pyrolyzing Cu-doped zeolitic-imidazolate-framework-8 polyhedrons, the obtained CuN/C catalyst can achieve a high specific surface area of 1182 m2 g-1 with a refined hierarchical porous structure and a high surface N content of 11.05 at%. Moreover, regulating the Cu loading can efficiently tune the states of Cu(II) and Cu0 , resulting in the successful construction of a highly active hybrid coordination site of NCu(II)Cu0 in derived CuN/C catalysts. As a result, the optimized 25% CuN/C catalyst possesses a high ORR activity and stability in 0.1 m KOH solution, as well as excellent performance and stability in a Zn-air battery.

Unveiling the Catalytic Origin of Nanocrystalline Yttrium Ruthenate Pyrochlore as a Bifunctional Electrocatalyst for Zn-Air Batteries.

Zn-air batteries suffer from the slow kinetics of oxygen reduction reaction (ORR) and/or oxygen evolution reaction (OER). Thus, the bifunctional electrocatalysts are required for the practical application of rechargeable Zn-air batteries. In terms of the catalytic activity and structural stability, pyrochlore oxides (A2[B2-xAx]O7-y) have emerged as promising candidates. However, a limited use of A-site cations (e.g., lead or bismuth cations) of reported pyrochlore catalysts have hampered broad understanding of their catalytic effect and structure. More seriously, the catalytic origin of the pyrochlore structure was not clearly revealed yet. Here, we report the new nanocrystalline yttrium ruthenate (Y2[Ru2-xYx]O7-y) with pyrochlore structure. The prepared pyrochlore oxide demonstrates comparable catalytic activities in both ORR and OER, compared to that of previously reported metal oxide-based catalysts such as perovskite oxides. Notably, we first find that the catalytic activity of the Y2[Ru2-xYx]O7-y is associated with the oxidations and corresponding changes of geometric local structures of yttrium and ruthenium ions during electrocatalysis, which were investigated by in situ X-ray absorption spectroscopy (XAS) in real-time. Zn-air batteries using the prepared pyrochlore oxide achieve highly enhanced charge and discharge performance with a stable potential retention for 200 cycles.

Single crystalline pyrochlore nanoparticles with metallic conduction as efficient bi-functional oxygen electrocatalysts for Zn–air batteries

We have shown that highly efficient metallic pyrochlore oxide nanoparticles (Pb2Ru2O6.5) exhibit outstanding activity as bi-functional electrocatalysts in aqueous Zn–air batteries for ORR and OER.

Simultaneous CO2 Reduction and Dye (Crystal Violet) Removal Electrochemically on Sn and Zn Electrocatalysts Using Co3O4 Anode

The simultaneous reduction of CO2 to product electrochemically (RCPE) was studied on Sn and Zn electrocatalysts and oxidation of dye (crystal violet (CV)) at Co3O4 electrocatalyst. The electrodes for anode and cathode were prepared by coating the electrocatalysts on the graphite surface. The experimental studies were done in aqueous 0.5 M NaHCO3 and KHCO3 electrolyte solutions with CV (10 ppm) at different applied voltages (2–3.8 V). The results in forming product and CV dye removal were shown in time intervals of 5, 10, 15, 20, and 25 min, respectively. However, HCOOH was the only reduced product formed from RCPE, along with removal of CV observed for the applied experimental conditions. High Faradaic efficiency of 45.33% for HCOOH at Zn electrocatalyst in KHCO3 solution was observed in reaction time of 5 min. Maximum dye removals for Sn and Zn electrocatalyst are reported to be 64.3 and 61% in NaHCO3 electrolyte solution, and similarly dye removals of 71.5 and 60.9% were obtained in KHCO3 electrolyte at...

Controllable localization of carbon nanotubes on the holey edge of graphene: an efficient oxygen reduction electrocatalyst for Zn–air batteries

An efficient oxygen reduction reaction (ORR) catalyst based on a three dimensional holey graphene framework with precise localization of N-doped carbon nanotubes (N-CNTs) on the hole-edges of graphene is demonstrated.

Spherical nitrogen-doped hollow mesoporous carbon as an efficient bifunctional electrocatalyst for Zn-air batteries.

Materials based upon porous carbon have gained considerable attention due to their high surface area, electric conductivity, thermal and chemical stability, low density, and availability. These superior properties make them ideal for diverse applications. Doping these carbon nanostructures holds promise of designing the properties of these structures and opening the door to practical applications. Herein, we report the preparation of hollow N-doped mesoporous carbon (HMC) spheres fabricated via polymerization and carbonization of dopamine on a sacrificial spherical SiO(2) template that is removed upon hydrofluoric acid etching. The morphology and structural features of these HMCs were evaluated using scanning electron microscopy and transmission electron microscopy and the N-doping (7.1 at%) was confirmed by X-ray photoelectron spectroscopy (XPS). The oxygen reduction/evolution reaction (ORR/OER) performance of N-doped HMC was evaluated using rotating disk electrode (RDE) voltammetry in an alkaline electrolyte. N-doped HMC demonstrated a high ORR onset potential of -0.055 V (vs. Hg/HgO) and excellent stability. The outstanding bifunctional activity was implemented in a practical Zn-air battery (ZAB), which exhibited a small charge-discharge voltage polarization of 0.89 V and high stability over repeated cycling.

Porous nitrogen doped carbon fiber with churros morphology derived from electrospun bicomponent polymer as highly efficient electrocatalyst for Zn–air batteries

Highly porous nitrogen doped carbon fibers like churros morphology are prepared from a simple and cost-effective fabrication process, electrospinning with bicomponent polymer consisting of polystyrene (PS) and polyacrylonitrile (PAN). From appropriate ratio of two polymer and pyrolysis at 1100 °C, newly churros morphology with extremely high surface area (1271 m2 g−1) is prepared. During carbonization, more unstable PS than PAN plays a critical role in forming such morphology by acting as sacrifice materials, thus providing additional formation of inner pores and outer etched surfaces. Furthermore, it demonstrates excellent electrocatalytic activity toward ORR, which is attributed to highly meso- and macro porous nitrogen-doped large surface area and enhanced graphitic-nitrogen groups of carbon fibers. For example, the performance of a Zn–air cell based on the nitrogen-doped porous carbon nanofibers exhibits a peak power density of 194 mW cm−2, comparable to that based on a commercial Pt/C catalyst (192 mW cm−2). Further, the generation of hydrogen peroxide ions (<20%) in a half cell is similar to that on the commercial Pt/C catalyst.

Ionic liquid modified graphene nanosheets anchoring manganese oxide nanoparticles as efficient electrocatalysts for Zn–air batteries

Ionic liquid (IL) modified reduced graphene oxide (rGO–IL) nanosheets anchoring manganese oxide (Mn3O4) are synthesized via a facile solution-based growth mechanism and applied to a Zn–air battery as an effective electrocatalyst for the oxygen reduction reaction (ORR). In this study, the IL moiety in these composites increases not only the conductivity of the system, but also the electrocatalytic activity compared to pristine rGO, together with the synergic effect of facilitating the ORR with the intrinsic catalytic activity of Mn3O4. Based on the Koutecky–Levich plot, we suggest that the ORR pathway of these composites is tunable with the relative amount of Mn3O4 nanoparticles supported onto the graphene sheets; for example, the ORR mechanism of the system with a lower Mn3O4 (19.2%) nanoparticle content is similar to a Pt/C electrode, i.e., a one-step, quasi-4-electron transfer, unlike that with a higher Mn3O4 (52.5%) content, which undergoes a classical two-step, 2-electron pathway. We also demonstrate the potential of these hybrid rGO–IL/Mn3O4 nanoparticles as efficient catalysts for the ORR in the Zn–air battery with a maximum peak power density of 120 mW cm−2; a higher performance than that from commercial cathode catalysts.

Microwave-assisted polyol synthesis of Pt–Zn electrocatalysts on carbon nanotube electrodes for methanol oxidation

Bimetallic Pt–Zn catalysts with high and stable electrochemical activity towards sulfuric acid and methanol oxidation were synthesized by microwave-assisted polyol (MP) method. A catalytic chemical vapor deposition was used to directly grow multi-layered carbon nanotubes (CNTs) on carbon paper substrate. The as-grown CNT forest serves as a support for the Pt–Zn catalysts having a mean size of 3–5 nm. The catalytic activities of the supported Pt–Zn catalysts toward acid electrolyte and methanol oxidation were examined by cyclic voltammetry test with potential cycling. Experimental results confirmed that two-stage MP synthesis enables the improvement of electrochemical activity, antipoisoning ability and long-term durability of the binary catalyst. This improvement can be attributed to the bifunctional mechanism of the binary catalysts: the Zn content serves as a promoting center for the generation of Zn–OH species, and more Pt sites are thus available for methanol oxidation. Accordingly, the Pt–Zn/CNT catalyst, prepared by the MP approach, displays a potential candidate for fuel cell application due to its easy fabrication (6 min), low cost and no additional reduction process.