Promotional effect of Ni–Co/ordered mesoporous carbon as non-noble hybrid electrocatalyst for methanol electro-oxidation

Nickel and cobalt-based tungstate nanocomposites as promising electrocatalysts in alkaline direct methanol fuel cells

In this work, a non-precious group metal (non-PGM) electrocatalyst based on transition metals is introduced as a promising solution for enhancing the efficiency of direct methanol fuel cell (DMFC). Nickel-cobalt mixed tungstate was prepared using a simple co-precipitation method with different molar ratios of Ni, Co and W. The prepared materials were tested and validated using different characterization techniques. It was observed using SEM that the materials are agglomerated amorphous random circular nanocomposite structures. The electrochemical performance of the prepared electrocatalysts revealed that the best nanocomposite was the one with the Ni : Co : W ratio of 1 : 1 : 1.5 (W1.5). This composite showed a higher current density of 229 mA cm-2 towards methanol oxidation at a scan rate of 50 mV s-1 in 1 M methanol at 0.6 V, with the lowest onset potential of 0.33 V. The obtained results present a new strong non-PGM material for direct methanol electro-oxidation reactions and open new doors for economic and earth-abundant electrocatalysts as an alternative to expensive commercially available catalysts.

Rational Design of NiZnx@CuO Nanoarray Architectures for Electrocatalytic Oxidation of Methanol

Methanol oxidation reaction (MOR) in anodes is one of the significant aspects of direct methanol fuel cells (DMFCs), which also plays a critical role in achieving a carbon-neutral economy. Designing and developing efficient, cost-effective, and durable non-Pt group metal-based methanol oxidation catalysts are highly desired, but a gap still remains. Herein, we report well-defined hierarchical NiZnx@CuO nanoarray architectures as active electrocatalysts for MOR, synthesized by combining thermal oxidation treatment and magnetron sputtering deposition through a brass mesh precursor. After systematically evaluating the electrocatalytic performance of NiZnx@CuO nanoarray catalysts with different preparation conditions, we found that the NiZn1000@CuO (thermally oxidized at 500 °C for 2 h, nominal thickness of the NiZn alloy film is 1000 nm) electrode delivers a high current density of 449.3 mA cm-2 at 0.8 V for MOR in alkaline media as well as excellent operation stability (92% retention after 12 h). These outstanding MOR performances can be attributed to the hierarchical well-defined structure that can not only render abundant active sites and a synergistic effect to enhance the electrocatalytic activity but also can effectively facilitate mass and electron transport. More importantly, we found that partial Zn atoms could leach from the NiZn alloy, resulting in rough surface nanorods, which would further increase the specific surface area. These results indicate that the NiZn1000@CuO nanoarray architecture could be a promising Pt group metal alternative as an efficient, cost-effective, and durable anode catalyst for DMFCs.

Facile Preparation of Porous Carbon Flake-Supported Nickel Nanoplates as Effective Catalysts for Methanol Electrooxidation

Herein, we report a facile and efficient method for fabricating porous carbon flakes (PCFs)-supported nickel nanoplates (Ni NPs) as electrocatalysts for methanol oxidation in alkaline media. The catalyst was fabricated in one step using molten salt synthesis. Various techniques were used to characterize the morphology and composition of the Ni NPs@PCFs catalyst, and these revealed that the Ni NPs were dispersed finely across the PCFs with a highly crystalline structure. The Ni NPs@PCFs catalyst demonstrated high electrocatalytic activity for methanol oxidation (121 mA/cm2 vs. Ag/AgCl), and it had an onset potential of 0.35 V. It also exhibited high stability in an alkaline electrolyte for the duration of the experiment (up to 2000 s).

Tragacanth Gum Hydrogel-Derived Trimetallic Nanoparticles Supported on Porous Carbon Catalyst for Urea Electrooxidation

The fabrication of electrocatalysts with high catalytic activity, high durability and low cost towards urea oxidation by a facile method is a great challenge. In this study, non-precious NiCoFe trimetallic supported on porous carbon (NiCoFe@PC) was prepared via gelation and pyrolysis method, presenting a remarkable electrocatalytic activity with low onset potential for urea oxidation in an alkaline medium. Field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were used to clarify the morphology of the NiCoFe@PC nanostructure and its nanoparticle size of 17.77 nm. The prepared catalyst with the composition ratio of 24.67, 5.92 and 5.11% for Ni, Fe and Co, respectively, with highly crystalline nanoparticles, fixed on porous carbon, according to energy-dispersive X-ray (EDX) and X-ray diffraction (XRD) analysis. The FeCoNi@PC catalyst showed a catalytic activity of 44.65 mA/cm² at 0.57 V vs. Ag/AgCl and a low onset potential of 218 mV, which is superior to many other transition bi/trimetallic-based catalysts previously reported.