NiCo alloy nanoparticles electrodeposited on an electrochemically reduced nitrogen-doped graphene oxide/carbon-ceramic electrode: a low cost electrocatalyst towards methanol and ethanol oxidation

In this work, nickel–cobalt alloy nanoparticles were electrodeposited on/in an electrochemically reduced nitrogen-doped graphene oxide (ErN-GO)/carbon-ceramic electrode (CCE) and the resulting nanocomposite (NiCo/ErN-GO/CCE) was evaluated as a low cost electrocatalyst for methanol and ethanol electrooxidation. Field-emission scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy were used for the physical characterization of the electrocatalyst. To study the electrochemical behavior and electrocatalytic activity of the prepared electrocatalyst towards the oxidation of methanol and ethanol in alkaline media, cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy were utilized. Electrochemical investigation of the introduced electrocatalysts (NiCo alloy and Ni nanoparticles alone electrodeposited on/in different substrates) indicated that NiCo/ErN-GO/CCE has highest activity and stability towards methanol (J_p = 88.04 mA cm⁻²) and ethanol (J_p = 64.23 mA cm⁻²) electrooxidation, which highlights its potential use as an anodic material in direct alcohol fuel cells.

NiCo alloy nanoparticles on the electrochemically reduced nitrogen-doped graphene oxide/carbon-ceramic electrode: a low cost electrocatalyst towards methanol and ethanol oxidation.     

Catalytic alcoholysis of alkaline extracted lignin for the production of aromatic esters over SO42−/ZrO2-ATP

An efficient process for the depolymerization of alkaline extracted lignin (AEL) using attapulgite (ATP)-supported solid catalysts in ethanol was developed in this work. Different ATP-supported catalysts were prepared and used to catalyze the depolymerization of the lignin AEL. The results demonstrated that the addition of ATP-supported catalysts was favorable for controlling the distribution of valuable depolymerization products. The optimal solid catalyst SO₄²⁻/ZrO₂-ATP (Cat 2) exhibited high catalytic activity and selectivity, which showed a 78.6% conversion of AEL and a 29.4% selectivity to ethyl ferulate (ethyl 4-hydroxy-3-methoxycinnamate) with a catalyst/AEL ratio of 1 : 1 at 200 °C for 120 min. The catalyst could be reused and its catalytic activity did not obviously decreased after 6 successive runs. Particularly, a plausible mechanism involving esterification, hydrogenation, and dehydration for the production of aromatic esters from AEL depolymerization over SO₄²⁻/ZrO₂-ATP in ethanol was also proposed.

An efficient process for the depolymerization of alkaline extracted lignin (AEL) using attapulgite (ATP)-supported solid catalysts in ethanol was developed in this work.     

Research on UO2 modification of a direct ethanol fuel cell Pt/C catalyst

Radioactive UO₂ powder was prepared by hydrothermal method and a set of Pt–xUO₂/C catalysts were synthesized by impregnation method for solving the problem of low activity and easy poisoning of anode Pt/C catalysts for a direct ethanol fuel cell. XRD, TEM, EDS, XPS and ICP-MS characterization showed the successful loading of Pt and UO₂ onto the carbon carrier. Electrochemical workstation and single cell test results confirm that the catalytic performance of Pt–10% UO₂/C is significantly better than Pt/C-eg. It is speculated that the synergistic effect of Pt and U enhances the catalytic activity and UO₂ improves the resistance to CO poisoning by releasing O₂ stored in the lattice space, while the α-particles released by ²³⁵U can also generate radiolysis product OH and promote the oxidative desorption of CO from the Pt surface.

The Pt–xUO₂/C catalyst modified by UO₂ in DEFC shows better catalytic activity, durability and resistance to CO poisoning ability than the anode Pt/C catalyst.     

Black phosphorous/palladium functionalized carbon aerogel nanocomposite for highly efficient ethanol electrooxidation

Direct ethanol fuel cells have great potential for practical power applications due to their easy operation, high energy density, and low toxicity. However, the slow and incomplete ethanol electrooxidation (EEO) reaction is a major drawback that hinders the development of this type of fuel cell. Here, we report a facile approach for the preparation of highly active, low cost and stable electrocatalysts based on palladium (Pd) nanoparticles and black phosphorus/palladium (BP/Pd) nanohybrids supported on a carbon aerogel (CA). The nanocomposites show remarkable catalytic performance and stability as anode electrocatalysts for EEO in an alkaline medium. A mass peak current density of 8376 mA mg_Pd⁻¹ is attained for EEO on the BP/Pd/CA catalyst, which is 11.4 times higher than that of the commercial Pd/C catalyst. To gain deep insight into the structure–property relationship associated with superior electroactivity, the catalysts are well characterized in terms of morphology, surface chemistry, and catalytic activity. It is found that the BP-doped CA support provides high catalyst dispersibility, protection against leaching, and modification of the electronic and catalytic properties of Pd, while the catalyst modifies CA into a more open and conductive structure. This synergistic interaction between the support and the catalyst improves the transport of active species and electrons at the electrode/electrolyte interface, leading to rapid EEO reaction kinetics.

A black phosphorus/palladium (BP/Pd) nanohybrid catalyst embedded in a carbon aerogel matrix exhibits remarkable electroactivity and durability for ethanol electrooxidation in an alkaline medium.     

Mechanistic effects of blending formic acid with ethanol on Pd activity towards formic acid oxidation in acidic media

The direct formic acid fuel cell (DFAFC) is one of the most promising direct liquid fuel cells. Pd is the most active catalyst towards formic oxidation, however, it suffers from CO-like poisoning and instability in acidic media. Blending formic acid with ethanol is known to synergistically enhance the Pt catalytic activity of Pt. However, it has not been studied in the case of Pd. In this study, ethanol/formic acid blends were tested, aiming at understanding the effect of ethanol on the formic acid oxidation mechanism at Pd and how the direct and indirect pathways could be affected. The blends consisted of different formic acid (up to 4 M) and ethanol (up to 0.5 M) concentrations. The catalytic activity of a 40% Pd/C catalyst was tested in 0.1 M H₂SO₄ + XFA + YEtOH using cyclic voltammetry, while the catalyst resistance to poisoning in the presence and absence of ethanol was tested using chronopotentiometry. The use of these blends is found to not only eliminate the indirect pathway but also slowly decrease the direct pathway activity too. That is believed to be due to the different ethanol adsorption orientations at different potentials. This study should open the door for further studying the oxidation of FA/ethanol blends using different pHs and different Pd-based catalysts.

Ethanol changes the Pd selectivity towards the different pathways of formic acid oxidation by eliminating the indirect pathway and slowly decreasing the direct pathway activity, owing to ethanol potential depdant adsorption orientations.     

Electrochemically dealloyed nanoporous Fe40Ni20Co20P15C5 metallic glass for efficient and stable electrocatalytic hydrogen and oxygen generation

The anion exchange membrane (AEM) in fuel cells requires new, stable, and improved electrocatalysts for large scale commercial production of hydrogen fuel for efficient energy conversion. Fe₄₀Ni₂₀Co₂₀P₁₅C₅, a novel metallic glass ribbon, was prepared by arc melting and melt spinning method. The metallic glass was evaluated as an efficient electrocatalyst in water-splitting reactions, namely hydrogen evolution reaction under acidic and alkaline conditions. In addition, oxygen evolution reaction in alkaline medium was also evaluated. In 0.5 M H₂SO₄, the metallic glass ribbons, after electrochemical dealloying, needed an overpotential of 128 mV for hydrogen evolution reaction, while in 1 M KOH they needed an overpotential of 236 mV for hydrogen evolution. For the oxygen evolution reaction, the overpotential was 278 mV. The electrochemical dealloying procedure significantly reduced the overpotential, and the overpotential remained constant over 20 hours of test conditions under acidic and alkaline conditions. The improved electrocatalytic activity was explained based on the metastable nature of metallic glass and the synergistic effect of metal hydroxo species and phosphates. Based on the excellent properties and free-standing nature of these metallic glass ribbons in electrolyte medium, we propose the current metallic glass for commercial, industrial electrocatalytic applications.

The anion exchange membrane (AEM) in fuel cells requires new, stable, and improved electrocatalysts for large scale commercial production of hydrogen fuel for efficient energy conversion.     

One-step synthesis of Ni(OH)2/MWCNT nanocomposites for constructing a nonenzymatic hydroquinone/O2 fuel cell

In this work, a H-type hydroquinone/O₂ fuel cell was assembled and shows high energy density in neutral phosphate buffer solution at moderate temperature. The anodic material, Ni(OH)₂/MWCNTs, was synthesized by a one-step hydrothermal synthesis method to oxidize hydroquinone. The cathode material, Pt/MWCNTs, was obtained by an electrodeposition method, and shows great oxygen reduction reaction (ORR) activity. The properties and the morphology of Ni(OH)₂/MWCNT nanocomposites were characterized by TEM, XPS, EDS-mapping and electrochemical methods, like cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results show that Ni(OH)₂/MWCNTs can effectively oxidize hydroquinone and play a dominant role in enhancing the fuel cell performance. The nonenzymatic fuel cell possesses a high power density of 0.24 mW cm⁻² at a cell potential of 0.49 V.

In this work, a H-type hydroquinone/O₂ fuel cell was assembled and shows high energy density in neutral phosphate buffer solution at moderate temperature.     

Synthesis of dimethyl carbonate from CO2 and methanol over a hydrophobic Ce/SBA-15 catalyst

A series of Ce/SBA-15 catalysts with different degrees of hydrophobicities were prepared via a post-grafting method and used for the direct synthesis of dimethyl carbonate (DMC) from CO₂ and methanol. The Ce/SBA-15-6 catalyst exhibited the highest DMC yield of 0.2%, which was close to the equilibrium value under the reaction conditions of 130 °C, 12 h and 12 MPa. The catalysts were characterized via XRD, BET, FT-IR, solid-state ²⁹Si MAS NMR, CA, TEM, XPS and NH₃/CO₂-TPD; the results indicated that the hydrophobicity of the catalysts facilitated the creation of oxygen vacancies, which could act as Lewis acids to activate methanol. Higher amounts of moderate acid sites led to higher yields of DMC. In addition, the hydrophobicity of the catalysts could also reduce the adsorbed water on their surface and increase the DMC yield while shortening the reaction time.

A series of Ce/SBA-15 catalysts with different degrees of hydrophobicities were prepared via a post-grafting method and used for the direct synthesis of dimethyl carbonate (DMC) from CO₂ and methanol.     

Fe/N codoped porous graphitic carbon derived from macadamia shells as an efficient cathode oxygen reduction catalyst in microbial fuel cells

In this study, Fe/N codoped porous graphitic carbon derived from macadamia shells was prepared at different temperatures as cathodic catalysts for microbial fuel cells (MFCs), with K₂FeO₄ as a bifunctional catalyst for porosity and graphitization. The catalyst prepared at 750 °C (referred to as MSAC-750) showed a large specific surface area (1670.3 m² g⁻¹), graphite structure, and high pyridine-N and Fe-N_X contents. Through the electrochemical workstation test, MSAC-750 shows excellent oxygen reduction reaction (ORR) activity, with an onset potential of 0.172 V and a half-wave potential of −0.028 V (vs. Ag/AgCl) in a neutral medium, and the ORR electron transfer number is 3.89. When applied to the MFCs as cathodic catalysts, a higher maximum power density and voltage of 378.68 mW m⁻² and 0.425 V were achieved with the MSAC-750 catalyst and is superior to that of the Pt/C catalyst (300.85 mW m⁻² and 0.402 V). In this case, a promising method is hereby established for the preparation of an excellent electrochemical catalyst for microbial fuel cells using inexpensive and easily available macadamia shells.

Fe/N codoped porous graphitic carbon derived from macadamia shells possessed good electrochemical performance as a cathode catalyst in microbial fuel cells.     

Heterostructure of vanadium pentoxide and mesoporous SBA-15 derived from natural halloysite for highly efficient photocatalytic oxidative desulphurisation

Integration between conventional semiconductors and porous materials can enhance electron–hole separation, improving photocatalytic activity. Here, we introduce a heterostructure that was successfully constructed between vanadium pentoxide (V₂O₅) and mesoporous SBA-15 using inexpensive halloysite clay as the silica–aluminium source. The composite material with 40% doped V₂O₅ shows excellent catalytic performance in the oxidative desulphurisation of dibenzothiophene (conversion of 99% with only a minor change after four-cycle tests). These results suggest the development of new catalysts made from widely available natural minerals that show high stability and can operate in natural light to produce fuel oils with ultra-low sulphur content.

New and robust catalysts made from natural minerals that can operate in sunlight to produce fuel oils with ultra-low-sulphur content.     

A highly stable and sensitive ethanol sensor based on Ru-decorated 1D WO3 nanowires

Decorating materials with noble metal catalysts is an effective method for optimizing the sensing performance of sensors based on tungsten trioxide (WO₃) nanowires. Ruthenium (Ru) exhibits excellent catalytic activity for oxygen adsorption/desorption and chemical reactions between gases and adsorbed oxygen. Herein, small Ru nanoparticles were uniformly distributed on the surface of one-dimensional WO₃ nanowires. The nanowires were prepared by the electrospinning method through an ultraviolet (UV) irradiation process, and decoration with Ru did not change their morphology. A sensor based on 4% Ru nanowires (NWs) shows the highest response (∼120) to 100 ppm ethanol, which was increased around 47 times, and the lowest ethanol detection limit (221 ppb) at a lower temperature (200 °C) displays outstanding repeatability and stability even after 45 days or in higher-humidity conditions. Moreover, it also has faster response–recovery features. The improvement in the sensing performance was attributed to the stable morphology of the nanowires, the sensitization effect of Ru, the catalytic effect of RuO₂ and the optimal atomic utilization efficiency. This work offers an effective and promising strategy for promoting the ethanol sensing performance of WO₃.

Decorating Ru does not effect the morphology of NWs, increased the oxygen vacancies, adsorbed oxygen. This strategy results in a better sensing performance (∼120 to 100 ppm ethanol was increased around 47 times at 200 °C) and humidity resistance.     

Enhanced performance and degradation of wastewater in microbial fuel cells using titanium dioxide nanowire photocathodes

This paper explores the decolorization of dye wastewaters and electricity generation using dual-chamber microbial fuel cells (MFCs) with titanium dioxide nanowire (TiO₂ NW) photocathodes. TiO₂ NW cathodes under ultraviolet light are observed to enhance the reduction of azo dye Active Red 30 (AR 30) and electricity generation. The analysis of electrochemical impedance spectra (EIS) indicates acceleration of the electron transfer processes of photoelectrode reduction by the photocatalysis of TiO₂ NWs, with polarization resistance of the photocathode being 10.45 Ω under light irradiation from 294 Ω in the dark. Ultraviolet-visible light spectroscopy shows that the maximum degradation of the MFCs is 78.1%; the azo bond of AR 30 may be cleaved by photoelectrons generated by light irradiation of the illuminated TiO₂ NW photocathode. The electricity produced by microbial fuel cells (MFCs) is expected to enhance the reductive decolorization of the azo dye AR 30 solution.

Active Red 30 was effectively removed in the cathode chamber of the microbial fuel cell.     

Cobalt-modified palladium nanocatalyst on nitrogen-doped reduced graphene oxide for direct hydrazine fuel cell

Nitrogen-doped reduced graphene oxide-supported palladium–cobalt nanoparticles (PdCo NPs/NrGO NSs) are synthesized and used as a high-performance and low-cost anodic catalyst for direct hydrazine–hydrogen peroxide fuel cells. The SEM and TEM images of PdCo NPs/NrGO NSs show the uniform metal nanoparticle distribution on the NrGO NSs. The reduction of the oxygen functional groups and the doping of the nitrogen atoms in the GO framework are confirmed by FT-IR and XRD spectroscopic studies. The Pd catalysts modified by Co exhibit a higher catalytic activity, lower onset potential, better durability, and lower impedance values than unmodified Pd catalysts for the electro-oxidation of hydrazine. The kinetic studies show a first-order reaction with an activation energy of 12.51 kJ mol⁻¹. A direct hydrazine–hydrogen peroxide fuel cell with PdCo NPs/NrGO NSs as anode and Pt/C as cathode provides an open circuit voltage of 1.76 V and a maximum power density of 148.58 mW cm⁻² at 60 °C, indicating that the PdCo NPs/NrGO NSs are an economical, high performance and reliable anode catalyst for the direct hydrazine–hydrogen peroxide fuel cell.

The superior catalytic activity and stability of a novel anodic PdCo NPs/NrGO NSs for HzOR are confirmed by half and signal cell investigations.     

Active oxygen species adsorbed on the catalyst surface and its effect on formaldehyde oxidation over Pt/TiO2 catalysts at room temperature; role of the Pt valence state on this reaction?

Pt/TiO₂ catalysts, prepared by reduction pretreatment, showed enhanced catalytic activities in formaldehyde oxidation. X-ray photoelectron spectroscopy analysis confirmed that catalytic activity was affected by Pt valence states in the Pt/TiO₂ catalyst. Using O₂ re-oxidation tests, we showed that there was a correlation between the area of oxygen consumed and the ratio of metallic Pt species on the catalyst surface. The O₂ re-oxidation ability was involved in the production of the adsorbed formate intermediate from HCHO, confirmed through diffuse reflectance infrared Fourier transform spectroscopy analysis. Furthermore, metallic Pt species were involved in the oxidation of adsorbed CO to CO₂.

Two catalyst factors were identified that affected the reaction rate in the room temperature oxidation of HCHO.     

Improved performance of self-reactivated Pt–ThO2/C catalysts in a direct ethanol fuel cell

A novel self-reactivated catalyst Pt–ThO₂/C was prepared for the first time by selecting radioactive material ThO₂ as the catalytic additive to address the low activity and toxicity of the anode Pt/C catalyst in a direct ethanol fuel cell. The catalytic activity and resistance to CO poisoning of Pt-6.67 wt%ThO₂/C were found to be superior to those of Pt/C–NaBH₄ in electrochemical workstation and single-cell tests. It is speculated that the exist of ThO₂ not only improves the catalytic activity via the synergistic effect of Pt and Th, but also produces a large amount of radiolysis products, OH radicals, due to ²³²Th which oxidatively desorbs CO from Pt–CO_ads and solves the CO poisoning problem.

Self-reactivation of Pt–ThO₂/C achieved by introducing radioactive material ThO₂ improves the performance of the original Pt/C catalyst.     

Tunable and convenient synthesis of highly dispersed Fe–Nx catalysts from graphene-supported Zn–Fe-ZIF for efficient oxygen reduction in acidic media

The development of low-cost, efficient and stable electrocatalysts for the oxygen reduction reaction (ORR) is desirable but remains a great challenge. We report a convenient and efficient synthesis approach of highly dispersed Fe–N_x catalysts for ORR. Typically, Fe–Zn-ZIF (zeolitic imidazolate frameworks) nanocrystals cast as precursor and graphene as supports, highly dispersed Fe–N_x species were fabricated with PVP (polyvinyl pyrrolidone) as surfactant via pyrolysis. With the help of graphene and surfactant, the agglomeration of iron particles has been avoided during pyrolysis, and the size and morphology of ZIF particles intercalating into the graphene layers can be regulated precisely as well. The amount of Fe–N_x active sites in C-rGO-ZIF catalyst arrived 4.29%, which is obviously higher than most monodispersed non-precious metal catalysts reported. The obtained C-rGO-ZIF catalyst exhibits a high onset potential of 0.89 V and a half-wave potential of 0.77 V, which is only 30 mV away from Pt/C in acidic media. The active sites of the catalyst was characterized and found to be the highly dispersed Fe–N_x species, large and accessible specific surface area of graphene and abundant active nitrogen atoms. When the C-rGO-ZIF catalyst was applied in the cathode of fuel cell, the power density can reach up to 301 mW cm⁻², which highlights a practical application potential on small power supplies.

A tunable and convenient synthesis approach of highly dispersed Fe–N_x catalysts for ORR in acidic media was reported.     

A DFT prediction of two-dimensional MB3 (M = V,Nb, and Ta) monolayers as excellent anode materials for lithium-ion batteries

Transition metal borides (MBenes) have recently drawn great attention due to their excellent electrochemical performance as anode materials for lithium-ion batteries (LIBs). Using the structural search code and first-principles calculations, we identify a group of the MB₃ monolayers (M = V, Nb and Ta) consisting of multiple MB₄ units interpenetrating with each other. The MB₃ monolayers with non-chemically active surfaces are stable and have metal-like conduction. As the anode materials for Li-ion storage, the low diffusion barrier, high theoretical capacity, and suitable average open circuit voltage indicate that the MB₃ monolayers have excellent electrochemical performance, due to the B₃ chain exposed on the surface improving the Li atoms'' direct adsorption. In addition, the adsorbed Li-ions are in an ordered hierarchical arrangement and the substrate structure remains intact at room temperature, which ensures excellent cycling performance. This work provides a novel idea for designing high-performance anode materials for LIBs.

The boron-exposed MB₃ monolayers (M = V, Nb and Ta) formed by interpenetrating MB₄ units have high Li-ion capacities.     

Appraisal of synthetic cationic Gemini surfactants as highly efficient inhibitors for carbon steel in the acidization of oil and gas wells: an experimental and computational approach

New cationic Gemini surfactant (CGS) molecules were synthesized and investigated as anticorrosive materials for carbon steel (CS) in 1 M HCl solution by chemical, electrochemical and theoretical studies such as DFT and MDS approaches. The anticorrosion efficacy increased with the increase in the CGS concentration. It reached 95.66% at 5 × 10⁻³ M of the CGS molecule using PDP measurements. PDP studies confirm that the CGS molecule acts as a mixed inhibitor. The EIS outcomes were explained by an equivalent circuit in which a constant phase element (CPE) rather than a double-layer capacitance (C_dl) was exploited to donate a more precise fit of the experimental outcomes. The CGS molecule follows the Langmuir isotherm as it is chemically adsorbed onto the surface of CS. To explore the kinetic and adsorption mechanisms, the thermodynamic characteristics of the activation and adsorption processes were assessed under the impact of temperature. Frontier molecular orbitals (FMOs) were achieved by the density functional theory (DFT) method. The study of interatomic interactions at the [CS (Fe(110))]/CGS level was discussed using molecular dynamics (MD) simulation.

New cationic Gemini surfactant (CGS) molecules were synthesized and investigated as anticorrosive materials for carbon steel (CS) in 1 M HCl solution by chemical, electrochemical and theoretical studies such as DFT and MDS approaches.     

Synthesis of size-controlled and highly monodispersed silica nanoparticles using a short alkyl-chain fluorinated surfactant

Highly monodispersed silica nanoparticles (SiNPs) were synthesised using a fluorinated surfactant, HOCH₂CH(CF₃)CO₂H, and its efficiency was compared with efficiencies of five other surfactants. The size of the SiNPs (∼50–200 nm) was controlled by controlling the surfactant amount. The short alkyl-chain fluoro surfactant was found to be more efficient at producing monodispersed SiNPs than its long alkyl-chain fluoro or non-fluorinated surfactant counterparts.

Shape, size, and morphology controlled synthesis of monodispersed silica nanoparticles using 3-hydroxy-2-(trifluoromethyl)-propanoic acid (MAF-OH) surfactant.     

Cu assisted loading of Pt on CeO2 as a carbon-free catalyst for methanol and oxygen reduction reaction

The widely studied Pt/C catalyst for direct methanol fuel cells (DMFCs) suffers severe carbon corrosion under operation, which undermines the catalytic activity and durability. It is of great importance to develop a carbon-free support with co-catalytic functionality for improving both the activity and durability of Pt-based catalysts. The direct loading of Pt on the smooth surface of oxides may be difficult. Herein, the Cu assisted loading of Pt on CeO₂ is developed. Cu pre-coated CeO₂ was facilely synthesized and Pt was electrochemically deposited to fabricate the carbon-free PtCu/CeO₂ catalyst. The PtCu/CeO₂ catalyst has a mass activity up to 1.84 and 1.57 times higher than Pt/C towards methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR), respectively. Better durability is also confirmed by chronoamperometry and accelerated degradation tests. The strategy in this work would be greatly helpful for developing an efficient carbon-free support of Pt-based catalysts for applications in DMFCs.

TEM images of the PtCu/CeO₂-21 catalyst. The scale bar in image (B) is 5 nm. Image (C) shows the area chosen for elemental mapping; image (D, E, and F) show the mapping of Ce, Cu, and Pt, respectively.