Graphene aerogel supported Pt-Ni alloy as efficient electrocatalysts for alcohol fuel oxidation

Deciphering promotion of MoP over MoC in Pt catalysts for methanol-assisted water splitting reaction

Molybdenum-based compounds show promising promotion effects on Pt catalysts for energy-relevant catalysis reactions. Herein, a more effective promotion effect of MoP than MoC was found in assisting Pt nanoparticles for methanol-assisted hydrogen generation in light of the strong metal-support interaction and synergistic effect between Pt and MoP/C nanospheres. Electrochemical analyses and theoretical calculations demonstrated that Pt-MoP/C facilitated the oxidation and removal of CO intermediates more effectively than Pt-MoC/C. This enhanced performance was attributed to the distinct 6-coordination environment of hexagonal MoP and the elevated electron density of Mo induced by phosphorus. These structural and electronic features significantly enhanced electron transfer to Pt, thereby creating strong metal-support interaction and synergistic effect to improve the overall catalytic efficiency. Especially, the unique activities of Moδ+ and Moδ- in the MoP modified the surface structure of Pt, lowered the Pt d-band center, and optimized the local chemical state of Pt atoms, which resulted in more optimized adsorption energy and charge transfer capabilities of intermediates. The Pt-MoP/C electrolyzer thus showed both lower cell voltage than that of Pt-MoC/C and Pt/C electrolyzers in water splitting and methanol-assisted water splitting for hydrogen generation. This study offers insightful information about the promotion effect of molybdenum-based compounds in Pt catalyst systems in energy-relevant catalysis reactions.

Solvothermal synthesis of PdCu nanorings with high catalytic performance for alcohol electrooxidation

Two-dimensional (2D) Pd-based nanostructures with a high active surface area and a large number of active sites are commonly used in alcohol oxidation research, whereas the less explored ring structure made of nanosheets with large pores is of interest. In this study, we detail the fabrication of PdCu nanorings (NRs) featuring hollow interiors and low coordinated sites using a straightforward solvothermal approach. Due to increased exposure of active sites and the synergistic effects of bimetallics, the PdCu NRs exhibited superior catalytic performance in both the ethanol oxidation reaction (EOR) and the ethylene glycol oxidation reaction (EGOR). The mass activities of PdCu NRs for EOR and EGOR were measured at 7.05 A/mg and 8.12 A/mg, respectively, surpassing those of commercial Pd/C. Furthermore, the PdCu NRs demonstrated enhanced catalytic stability, maintaining higher mass activity levels compared to other catalysts during stability testing. This research offers valuable insights for the development of efficient catalysts for alcohol oxidation.

Nickel-cobalt alloy nanosheet-decorated three-dimensional titanium dioxide nanobelts electrodeposited on titanium meshes for boosting selective nitrate electroreduction to ammonia

Electrocatalytic nitrate reduction reaction presents a promising avenue for environmentally friendly ammonia (NH3) synthesis and wastewater treatment. An essential aspect to consider is the meticulous design of electrocatalysts. This study explores the utilization of a Ni-Co alloy nanosheet-decorated three-dimensional titanium dioxide (3D-TiO2) nanobelts electrodeposited on titanium meshes (NixCoy@TiO2/TM) for efficient electrocatalytic NH3 production. The optimized Ni1Co3@TiO2/TM electrode achieves a significant NH3 yield of 676.3 ± 27.1 umol h-1 cm-2 with an impressive Faradaic efficiency (FE) of 95.1 % ± 2.1 % in a 0.1 M KOH solution containing 0.1 M NO3- at -0.4 V versus the reversible hydrogen electrode. Additionally, the electrode demonstrates exceptional electrochemical activity for NH3 synthesis in simulated wastewater, delivering an outstanding NH3 yield of 751.6 ± 44.3 umol h-1 cm-2 with a FE of 96.8 % ± 0.4 % at the same potential of -0.4 V. Moreover, the electrode exhibits minimal variation in current density, NH3 yields and FEs throughout the 24-h stability test and the 20-cycle test, demonstrating its excellent stability and durability. This study offers a straightforward electrodeposited approach for the development of 3D-nanostructured alloys as catalysts for NH3 electrosynthesis from nitrates at room temperature.

PtRu mesoporous nanospheres as electrocatalysts with enhanced performance for oxidation of methanol

Composition and morphology are crucial factors in the design of Pt-based catalysts with high performance, particularly in direct methanol fuel cells (DMFCs). Herein, PtRu mesoporous nanospheres (PtRu MNs) with tunable compositions were synthesized via a facile method and then deposited on a carbon support to act as electrocatalyst materials for the methanol oxidation reaction (MOR). Superior catalytic activity, better catalytic stability, and good tolerance to CO were achieved by the optimum PtRu (2 : 1) MNs/C catalyst compared with Pt MNs/C. The mass activity on PtRu (2 : 1) MNs/C reached 111.77 mA mgPt -1, which was approximately 6.45-fold higher than that of Pt MNs/C (17.33 mA mgPt -1). Meanwhile, PtRu (2 : 1) MNs/C retained much more current density (84.7%) than Pt MNs/C (17.7%) after 500 cycles. The improved catalytic performance is due to several factors, including the formation of a mesoporous nanostructure with abundant active sites and the favorable effects of the Ru species. This work provides guidance toward designing and fabricating effective Pt-based electrocatalysts for DMFC applications.

Bi2Te3 nanosheets promoted Pd for ethylene glycol electrooxidation both in the dark and under visible light irradiation

Ethylene glycol electrooxidation catalyzed by Pd nanoparticles was found to be largely improved by Bi2Te3 nanosheets both in the dark and under visible light irradiation.

Carbon-Supported High-Loading Sub-4 nm PtCo Alloy Electrocatalysts for Superior Oxygen Reduction Reaction

Increasing the loading density of nanoparticles on carbon support is essential for making Pt-alloy/C catalysts practical in H2-air fuel cells. The challenge lies in increasing the loading while suppressing the sintering of Pt-alloy nanoparticles. This work presents a 40% Pt-weighted sub-4 nm PtCo/C alloy catalyst via a simple incipient wetness impregnation method. By carefully optimizing the synthetic conditions such as Pt/Co ratios, calcination temperature, and time, the size of supported PtCo alloy nanoparticles is successfully controlled below 4 nm, and a high electrochemical surface area of 93.8 m2/g is achieved, which is 3.4 times that of commercial PtCo/C-TKK catalysts. Demonstrated by electrochemical oxygen reduction reactions, PtCo/C alloy catalysts present an enhanced mass activity of 0.465 A/mg at 0.9 V vs. RHE, which is 2.0 times that of the PtCo/C-TKK catalyst. Therefore, the developed PtCo/C alloy catalyst has the potential to be a highly practical catalyst for H2-air fuel cells.

Ga-Modification Near-Surface Composition of Pt-Ga/C Catalyst Facilitates High-Efficiency Electrochemical Ethanol Oxidation through a C2 Intermediate

In electrochemical ethanol oxidation reactions (EOR) catalyzed by Pt metal nanoparticles through a C2 route, the dissociation of the C-C bond in the ethanol molecule can be a limiting factor. Complete EOR processes producing CO2 were always exemplified by the oxidative dehydrogenation of C1 intermediates, a reaction route with less energy utilization efficiency. Here, we report a Pt3Ga/C electrocatalyst with a uniform distribution of Ga over the nanoparticle surface for EOR that produces CO2 at medium potentials (>0.3 V vs SCE) efficiently through direct and sustainable oxidation of C2 intermediate species, i.e., acetaldehyde. We demonstrate the excellent performance of the Pt3Ga-200/C catalyst by using electrochemical in situ Fourier transform infrared reflection spectroscopy (FTIR) and an isotopic labeling method. The atomic interval structure between Pt and Ga makes the surface of nanoparticles nonensembled, avoiding the formation of poisonous *CHx and *CO species via bridge-type adsorption of ethanol molecules. Meanwhile, the electron redistribution from Ga to Pt diminishes the *O/*OH adsorption and CO poisoning on Pt atoms, exposing more available sites for interaction with the C2 intermediates. Furthermore, the dissociation of H2O into *OH is facilitated by the high hydrophilicity of Ga, which is supported by DFT calculations, promoting the deep oxidation of C2 intermediates. Our work represents an extremely rare EOR process that produces CO2 without observing kinetic limitations under medium potential conditions.

Simple pyrolysis of graphene-wrapped PtNi nanoparticles supported on hierarchically N-doped porous carbon for sensitive detection of carbendazim

A novel electrochemical sensor was established based on graphene-wrapped PtNi nanoparticles supported on three-dimensional (3D) N-doped porous carbon (G-PtNi/3D-NPC) for the highly sensitive and selective detection of carbendazim (CBZ). In this sensing system, the encapsulation of PtNi nanoparticles (NPs) by graphene can effectively prevent the aggregation tendency and enhance the structural stability. The hierarchically porous nanostructures have a large specific surface area to expose a large number of active sites and the resulting enhanced electrical conductivity ultimate improves the electrocatalytic activity towards CBZ. Under the optimal conditions, the prepared sensor showed excellent electrochemical responses for the determination of CBZ with a linear range of 0.5-30 μM and lower limit of detection (LOD) of 0.04 μM (S/N = 3). It also shows excellent anti-interference ability at a working potential of 0.74 V. The feasibility of the senor is demonstrated for its practical assays in diluted peach and vegetable samples with acceptable recovery (95.8-97.3 %, peach; 97.2-97.6 %, vegetable) and a relative standard deviation (RSD) below 2.3%.

ZIF-67-derived CoP/NC effectively supported Pt nanoparticles for methanol oxidation reaction

Metal-support interaction plays an important role in the catalysis reaction, and an effective support is highly desired in the hybrid catalyst construction. Herein, we demonstrated an effective catalyst system by coupling Pt nanoparticles over the ZIF-67-derived CoP/NC support for methanol oxidation reaction (MOR) in acidic and alkaline solutions. The results indicated that the Pt-CoP/NC catalyst showed high catalytic activity and stability for MOR owing to the oxophilic properties of CoP and the strong metal-support interaction, as well supported by the electrochemical measurements and the spectroscopic analysis, which far exceeded that of the Pt-Co/NC and commercial Pt/C catalysts. Specifically, the forward peak current density of the Pt-CoP/NC catalyst was 74.2 mA cm^-2 for MOR in an acidic electrolyte, which was 2.2 times higher than that of a commercial Pt/C catalyst. Further, in an alkaline electrolyte, the Pt-CoP/NC catalyst showed the highest forward peak current density of 118.6 mA cm^-2, which was 4.5 times higher than that of a commercial Pt/C catalyst. High catalytic kinetics and stability for MOR were also carefully discussed. Moreover, the Pt-CoP/NC catalyst exhibited excellent anti-poisoning ability in comparison to the Pt-Co/NC and commercial Pt/C catalysts with the help of the CO-stripping technique. The current work would be instructive for high-performance catalyst system construction based on the ZIF-67-derived CoP/NC support.

Engineering Heterostructured Pd-Bi2Te3 Doughnut/Pd Hollow Nanospheres for Ethylene Glycol Electrooxidation

The electrooxidation of ethylene glycol (EG) is of vital significance for the conversion from biomass energy into electrical energy via direct fuel cells. However, the EG oxidation reaction (EGOR) suffers from poor efficiency due to the limitation of high-performance electrocatalysts for cleaving the C-C bonds. Herein, this limitation is successfully addressed by fabricating the doughnut-shaped Pd-Bi₂Te₃ heterostructured catalyst. Notably, the heterojunction Pd-Bi₂Te₃ nanocatalyst has been demonstrated to be highly active toward the EGOR with superb activity and durability, in which a mass activity as high as 2420.8 mA mg^-1 is achieved in alkaline media, being 1.7 times higher than that of the commercial Pd/C catalyst. Upon combination of experimental results with mechanism studies, it is indicated that the remarkable EGOR performance is attributed to the enlarged active areas that stemmed from the doughnut-like structure, as well as the strong synergistic effect from Pd-Bi₂Te₃ and Pd. More importantly, the highly electroactive Pd-Bi₂Te₃ can accelerate charge transfer and boost the oxidation of CO-like intermediates, which are conducive to the enhancement in electrochemical stability.

Pd17Se15 alloy on Se sphere with high anti-poisoning ability for alcohol fuel electrooxidation

Electron-deficient effect of Pd in the Pd17Se15 catalyst effectively weakens the adsorption of CO poisoning species and enhances the electrocatalytic performance of alcohol electrooxidation in an alkaline medium.