Electrochemically modified boron-doped diamond electrode with Pd and Pd-Sn nanoparticles for ethanol electrooxidation

Fe-Pd nanoflakes decorated on leached graphite disks for both methanol and formic acid electrooxidation with excellent electrocatalytic performance

This paper introduces a unique and simple method for fabricating of inexpensive electrocatalysts for use in direct methanol fuel cells. The leached Fe1-Pd1 NFs/graphite (leached Fe1-Pd1/graphite) disk electrode was successfully obtained via uniform dispersion of Zn powder into the matrix of commercial graphite powder (98%), pressing under optimized pressure followed by the treatment in H2SO4 solution containing Fe+2 and Pd+2 cations, leading to the partial leaching out of Zn from graphite matrix, as well as partial electroless substitution of Fe-Pd nanoflakes with Zn metal. Based on the morphology studies, binary Fe-Pd nanoflakes with a large surface area uniformly dispersed on the leached graphite disk. The leached Fe-Pd/G disk showed the exceptional electrocatalytic activity toward methanol and formic acid oxidation without electrocatalyst poisoning being observed, in contrast to the leached Pd/graphite and leached Fe/graphite disks. This is due to the high surface area, and synergistic effect of Pd and Fe. The findings of this work may be used for the mass manufacture of graphite-based disks for commercial fuel cell applications using available graphite powders. The linear range of washed Fe1-Pd1/G electrocatalyst for measuring methanol was about 0.1-1.3 M, and its detection limit was calculated at about 0.03 M. Furthermore, the linear range of the nanocatalyst for measuring formic acid was about 0.02-0.1 M, and its detection limit was calculated at about 0.006 M.

Core-shell copper-gold nanoparticles modified at the boron-doped diamond electrode for oxygen sensors

Bimetallic copper-gold (Cu@Au) nanoparticles were synthesized and utilised to modify boron-doped diamond (BDD) electrodes. Nanorod particles with a diameter size of around 10 nm and a length of around 20 nm were successfully synthesized. These nanoparticles were then attached to the BDD surface by using allylamine as the bridge. Comparison among the BDD modified with Cu@Au and individual gold nanoparticles showed that Cu@Au nanoparticles created around 3 times higher gold coverage on the BDD surface than normal gold nanoparticles. It was also found that the use of allylamine as the bridge can attach more gold than copper nanoparticles. Moreover, around two times higher current responses of oxygen reduction reaction were observed at Cu@Au-modified BDD. Good linearity in a concentration range from 2 to 9 ppm could be achieved with a sensitivity of 0.0138 mA ppm^-1 and limit detection of 1.98 ppm. An application of the modified BDD for a biochemical oxygen demand (BOD) sensor using Rhodotorula mucilaginosa UICC Y-181 as the biosensing agent was also demonstrated with glucose solutions as the solution model. Sensitivity equivalent to 17.4 μA mM^-1 BOD could be achieved. The system showed good stability with an RSD of 3.45% in 10 measurements.

Synthesis and Characterization of Supported Pd Catalysts for Potential Application in Glycerol Electro-Oxidation

Ceria-supported Pd catalysts encompassing oxides of Cu, Co, and Fe were synthesized and characterized using XRD, TEM, SEM-EDX, TPR, BET, and Raman. After the incorporation of the metal oxides, the surface area and pore volume of the ceria support decreased. XRD showed the presence of the metal oxide phases as well as the support, CeO2. TPR showed that the bimetallic catalyst had improved reducibility compared to the monometallic Pd/CeO2. TEM images showed irregular-shaped particles with an average size distribution of 2–10 nm. SEM-EDX showed that the metal oxides were evenly distributed over the surface of the support. The electro-oxidation of glycerol in an alkaline environment was evaluated using cyclic voltammetry, and the products formed were identified and quantified using GC-MS. Glyceric acid was the dominant product over Pd-CuO/CeO2, while glyceraldehyde and dihydroxyacetone were dominant over Pd-Co3O4/CeO2 and Pd-Fe2O3/CeO2, respectively.

Progress in the Development of Electrodeposited Catalysts for Direct Liquid Fuel Cell Applications

Fuel cells are a key enabling technology for the future economy, thereby providing power to portable, stationary, and transportation applications, which can be considered an important contributor towards reducing the high dependencies on fossil fuels. Electrocatalyst plays a vital role in improving the performance of the low temperature fuel cells. Noble metals (Pt, Pd) supported on carbon have shown promising performance owing to their high catalytic activity for both electroreduction and electrooxidation and have good stability. Catalyst preparation by electrodeposition is considered to be simple in terms of operation and scalability with relatively low cost to obtain high purity metal deposits. This review emphasises the role of electrodeposition as a cost-effective method for synthesising fuel cell catalysts, summarising the progress in the electrodeposited Pt and Pd catalysts for direct liquid fuel cells (DLFCs). Moreover, this review also discusses the technological advances made utilising these catalysts in the past three decades, and the factors that impede the technological advancement of the electrodeposition process are presented. The challenges and the fundamental research strategies needed to achieve the commercial potential of electrodeposition as an economical, efficient methodology for synthesising fuel cells catalysts are outlined with the necessary raw materials considering current and future savings scenario.

Nonmetal-doping of noble metal-based catalysts for electrocatalysis

In response to the shortage of fossil fuels, efficient electrochemical energy conversion devices are attracting increasing attention, while the limited electrochemical performance and high cost of noble metal-based electrode materials remain a daunting challenge. The electrocatalytic performance of electrode materials is closely bound with their intrinsic electronic/ionic states and crystal structures. Apart from the nanoscale design and conductive composite strategies, heteroatom doping, particularly for nonmetal doping (e.g., hydrogen, boron, sulfur, selenium, phosphorus, and tellurium), is also another effective strategy to greatly promote the intrinsic activity of the electrode materials by tuning their atomic structures. From the perspective of electrocatalytic reactions, the effective atomic structure regulation could induce additional active sites, create rich defects, and optimize the adsorption capability, thereby contributing to the promotion of the electrocatalytic performance of noble metal-based electrocatalysts. Encouraged by the great progress achieved in this field, we have reviewed recent advancements in nonmetal doping for electrocatalytic energy conversion. Specifically, the doping effect on the atomic structure and intrinsic electronic/ionic state is also systematically illustrated and the relationship with the electrocatalytic performance is also investigated. It is believed that this review will provide guidance for the development of more efficient electrocatalysts.

Black Phosphorus-Graphene Heterostructure-Supported Pd Nanoparticles with Superior Activity and Stability for Ethanol Electro-oxidation

Rational design supporting material for palladium (Pd)-based catalyst can maximize its electrocatalytic performance for ethanol oxidation reaction (EOR) catalyst in alkaline condition. Utilizing the unique two-dimensional structures and outstanding physicochemical property of graphene and black phosphorus (BP), herein, we proposed and designed a black phosphorus-graphene heterostructure for supporting Pd nanoparticles. Through merely ball-milling of activated graphene (AG) and black phosphorus (BP), the AG-BP hybrid with a linkage of P-C bonding is used as supports of Pd. The obtained Pd/AG-BP hybrid exhibits ultrahigh electrochemical activity toward EOR. Remarkably, it can achieve a high mass peak current density of ∼6004.53 and ∼712.03 mA mg_Pd^-1 before and after the durability tests of 20 000s on EOR, which are ∼7.19 and 80 times higher than those of commercial Pd/C. The experimental analysis and density-functional-theory calculation show that Pd becomes more positive with electrons transfer from Pd to AG-BP supports and is liable to absorb the OH radicals for removing CO_ads intermediate to release active sites on EOR, together with the excellent ability to generate additional OH militants after combining with the AG-BP heterostructure.

Surface-modified Pt1Ni1–Ni(OH)2 nanoparticles with abundant Pt–Ni(OH)2 interfaces enhance electrocatalytic properties

Pt₁Ni₁–Ni(OH)₂ NPs with abundant Pt–Ni(OH)₂ interfaces exhibit a rather high activity and stability for the MOR in alkaline electrolytes.

Boron-doped diamond nanowire array electrode with high mass transfer rates in flow-by operation

We fabricated a boron-doped diamond nanowire (BDDNW) array electrode via soft lithography and metal-assisted chemical etching (MACE) of Si to provide a highly promoted effective surface area and increased mass transport during the electrochemical oxidation process. The effects of aligning the BDDNW on the electrochemical oxidation performance and the current efficiency of the electrode in phenol oxidation were examined. Although the effective surface area of the BDDNW array with an aligned nanowire configuration was smaller than that of the BDDNW with a random nanowire configuration, the BDDNW array electrode exhibited a higher mass transfer coefficient, resulting in a better performance in the removal of phenol. The enhanced mass transport exhibited by the BDDNW array electrode also greatly enhanced the chemical oxygen demand (COD) and current efficiency. Furthermore, because of its excellent oxidation performance, the BDDNW array electrode also exhibited much lower energy consumption during the phenol oxidation process.