Modifying candle soot with FeP nanoparticles into high-performance and cost-effective catalysts for the electrocatalytic hydrogen evolution reaction

Sparkling Synergy: Enhancing Hydrogen Evolution with a Mesoporous CoP/FeP Interface

The reaction kinetics is predominantly determined by the surface and interface engineering of electrocatalysts. Herein, we demonstrate the growth of cobalt monophosphide and iron monophosphide (CoP/FeP) with an effective solid interface. The surface of CoP/FeP is mesoporous, which is obtained by phosphidizing mesoporous CoFe2O4. The CoP/FeP electrode exhibits substantially superior hydrogen evolution reaction (HER) performance compared to CoP and FeP. The overpotentials (η) required to generate 10 mA cm-2 are determined to be around 98 mVRHE (CoP/FeP), 220 mVRHE (FeP), and 265 mVRHE (CoP) in an acidic electrolyte. The exchange current density and Tafel slopes suggest that CoP/FeP has better redox properties and kinetic abilities compared to FeP and CoP. Furthermore, the CoP/FeP electrode exhibits reduced electrochemical impedance and superior surface charge transport characteristics in comparison to both the CoP and FeP electrodes. In addition to having a greater number of catalytically active sites, the turnover frequency of CoP/FeP is approximately 2 and 5 times higher than that of FeP and CoP, respectively. The CoP/FeP electrode maintains a consistent current density of around 25 mA cm-2 for a continuous period of 24 h during the HER, attesting to the excellent durability of the CoP/FeP electrode. In addition, a relationship between differential hydrogen adsorption energy (ΔEH), the corresponding Gibbs free energy change (ΔGH), and the hydrogen coverage on distinct surfaces, namely, CoP, FeP, and CoP/FeP, is established. The calculation findings show that the CoP/FeP surface, which is predominantly exposed with CoP, exhibits the highest catalytic potential for the HER. The estimation of the specific HER activity of the electrodes, normalized to the electrochemically active surface area, corroborates the calculation findings.

Enhanced Performance of Laser-Induced Graphene Supercapacitors via Integration with Candle-Soot Nanoparticles

Laser-induced graphene (LIG) has been emerging as a promising electrode material for supercapacitors due to its cost-effective and straightforward fabrication approach. However, LIG-based supercapacitors still face challenges with limited capacitance and stability. To overcome these limitations, in this work, we present a novel, cost-effective, and facile fabrication approach by integrating LIG materials with candle-soot nanoparticles. The composite electrode is fabricated by laser irradiation on a Kapton sheet to generate LIG material, followed by spray-coating with candle-soot nanoparticles and annealing. Materials characterization reveals that the annealing process enables a robust connection between the nanoparticles and the LIG materials and enhances nanoparticle graphitization. The prepared supercapacitor yields a maximum specific capacitance of 15.1 mF/cm2 at 0.1 mA/cm2, with a maximum energy density of 2.1 μWh/cm2 and a power density of 50 μW/cm2. Notably, the synergistic activity of candle soot and LIG surpasses the performances of previously reported LIG-based supercapacitors. Furthermore, the cyclic stability of the device demonstrates excellent capacitance retention of 80% and Coulombic efficiency of 100% over 10000 cycles.

Candle Soot as a Novel Support for Nickel Nanoparticles in the Electrocatalytic Ethanol Oxidation

The enhancement of carbon-supported components is a crucial factor in augmenting the interplay between carbon-supported and metal-active components in the utilization of catalysts for direct ethanol fuel cells (DEFCs). Here, we propose a strategy for designing a catalyst by modifying candle soot (CS) and loading nickel onto ordered carbon soot. The present study aimed to investigate the effect of the Ni nanoparticles content on the electrocatalytic performance of Ni-CS, ultimately leading to the identification of a maximum composition. The presence of an excessive quantity of nickel particles leads to a decrease in the number of active sites within the material, resulting in sluggishness of the electron transfer pathway. The electrocatalyst composed of nickel and carbon support, with a nickel content of 20 wt%, has demonstrated a noteworthy current activity of 18.43 mA/cm2, which is three times that of the electrocatalyst with a higher nickel content of 25 wt%. For example, the 20 wt% Ni-CS electrocatalytic activity was found to be good, and it was approximately four times higher than that of 20 wt% Ni-CB (nickel-carbon black). Moreover, the chronoamperometry (CA) test demonstrated a reduction in current activity of merely 65.80% for a 20 wt% Ni-CS electrocatalyst, indicating electrochemical stability. In addition, this demonstrates the great potential of candle soot with Ni nanoparticles to be used as a catalyst in practical applications.

Water electrolysis: from textbook knowledge to the latest scientific strategies and industrial developments

Replacing fossil fuels with energy sources and carriers that are sustainable, environmentally benign, and affordable is amongst the most pressing challenges for future socio-economic development. To that goal, hydrogen is presumed to be the most promising energy carrier. Electrocatalytic water splitting, if driven by green electricity, would provide hydrogen with minimal CO2 footprint. The viability of water electrolysis still hinges on the availability of durable earth-abundant electrocatalyst materials and the overall process efficiency. This review spans from the fundamentals of electrocatalytically initiated water splitting to the very latest scientific findings from university and institutional research, also covering specifications and special features of the current industrial processes and those processes currently being tested in large-scale applications. Recently developed strategies are described for the optimisation and discovery of active and durable materials for electrodes that ever-increasingly harness first-principles calculations and machine learning. In addition, a technoeconomic analysis of water electrolysis is included that allows an assessment of the extent to which a large-scale implementation of water splitting can help to combat climate change. This review article is intended to cross-pollinate and strengthen efforts from fundamental understanding to technical implementation and to improve the 'junctions' between the field's physical chemists, materials scientists and engineers, as well as stimulate much-needed exchange among these groups on challenges encountered in the different domains.

An expanded sandwich-like heterostructure with thin FeP nanosheets@graphene via charge-driven self-assembly as high-performance anodes for sodium ion battery

In this work, we simply fabricate a novel expanded sandwich-like heterostructure of iron-phosphide nanosheets in between reduced graphene oxide (expanded FeP NSs@rGO) with a high ratio of FeP/Fe-PO_x and an expanded structure via a charge-driven self-assembly method by exploiting polystyrene beads (PSBs) as a sacrificial template. In such a design, even after the decomposition of PSBs during the annealing process, the PSBs successfully provide ample space between the nanosheets, enabling a structure with long-term stability and high ionic conductivity. Importantly, the PSBs are decomposed and simultaneously reacted with oxidized iron-phosphide (Fe-PO_x) on the surface of the nanosheets to reduce into FeP. As a result, the expanded FeP NSs@rGO results in a high content of FeP (52.3%) and remarkable electrochemical performances when it is used for sodium-ion battery anodes. The expanded FeP NSs@rGO exhibits a high capacity of 916.1 mA h g^-1 at 0.1 A g^-1, a superior rate capability of 440.9 mA h g^-1 at 5 A g^-1, and a long-term cycling stability of 85.4% capacity retention after 1000 cycles at 1 A g^-1. In addition, the full cell also exhibits excellent capacity, rate capability, and cycling stability. This study clearly demonstrates that an increase in FeP proportion is directly related to an increase in capacity. This facile method of synthesizing rationally designed heterostructures is expected to provide a novel strategy to create nanostructures for advanced energy storage applications.

Nonmetallic Active Sites on Nickel Phosphide in Oxygen Evolution Reaction

Efficient and durable catalysts are crucial for the oxygen evolution reaction (OER). The discovery of the high OER catalytic activity in Ni12P5 has attracted a great deal of attention recently. Herein, the microscopic mechanism of OER on the surface of Ni12P5 is studied using density functional theory calculations (DFT) and ab initio molecular dynamics simulation (AIMD). Our results demonstrate that the H2O molecule is preferentially adsorbed on the P atom instead of on the Ni atom, indicating that the nonmetallic P atom is the active site of the OER reaction. AIMD simulations show that the dissociation of H from the H2O molecule takes place in steps; the hydrogen bond changes from Oa-H⋯Ob to Oa⋯H-Ob, then the hydrogen bond breaks and an H+ is dissociated. In the OER reaction on nickel phosphides, the rate-determining step is the formation of the OOH group and the overpotential of Ni12P5 is the lowest, thus showing enhanced catalytic activity over other nickel phosphides. Moreover, we found that the charge of Ni and P sites has a linear relationship with the adsorption energy of OH and O, which can be utilized to optimize the OER catalyst.

Facile synthesis of N-doped carbon nanoframes encapsulated by CoP nanoparticles for hydrogen evolution reaction

Development of high-performance, economic, and stable non-noble metal catalysts is a still formidable challenge in hydrogen evolution reaction (HER) that must be overcome to alleviate the energy and environmental crisis. Herein, we designed and fabricated N-doped carbon nanoframes encapsulated by CoP nanoparticles (CoP-NCN). The 3D porous structure of the ZIF-67-derived N-doped carbon shortened the charge and mass transport pathways, contributing to enhanced electrocatalytic performance. Moreover, the synergistic effects of excellent conductivity, abundant mesopores, and high-activity CoP nanoparticles led to remarkable electrocatalytic activity toward HER with an extremely low overpotential of 120 mV at 10 mA cm^-2 and long-term stability. We further indicate that the fantastic HER catalytic ability of CoP-NCN is attributed to the good conductivity and the abundant active sites. The present study provides a promising avenue toward the design of cost-effective HER electrocatalysts.

Continuous Roll-to-Roll Production of Carbon Nanoparticles from Candle Soot

Carbon nanoparticles (CNPs) have been considered as essential components for various applications including sensors, quantum dots, electrocatalysts, energy storages, lubrication, and functional coatings. Uniform and functional CNP materials can be obtained from candle soot. However, the production of CNPs from candle soot is not a continuous process, limiting the practical production and applications of such materials. Here, a rotating-deposition and separation system for high-efficiency production of low-cost and high-quality CNPs from candle soot is presented. The characteristic of CNPs can be controlled by adjusting the system parameters. Moreover, obtained CNPs can act as photothermal superhydrophobic anti-icing coatings on various substrates. With a sliding angle of less than 3°, water drops can keep rolling off without further nucleation of ice. The reported preparing method is suitable for large-scale applications and various kinds of surfaces and shows great potentials in the growing demands of anti-icing.

Multifunctional superhydrophobic adsorbents by mixed-dimensional particles assembly for polymorphic and highly efficient oil-water separation

Supra-wetting materials, especially superhydrophobic absorption materials, as an emerging advanced oil-water separation material have attracted extensive concern in the treatment of oil spillage and industrial oily wastewater. However, it is still a challenge to fabricate robust and multifunctional superhydrophobic materials for the multitasking oil-water separation and fast clean-up of the viscous crude oil by an environment-friendly and scalable method. Herein, a solid-solid phase ball-milling strategy without chemical reagent-free modification was proposed to construct heterogeneous superhydrophobic composites by using waste soot as the solid-phase superhydrophobic modifier. A series of covalent bond restricted soot-graphene (S-GN) or soot-Fe₃O₄ (S-Fe₃O₄) composite materials with a peculiar micro-nano structure are prepared. Through "glue+superhydrophobic particles" method, the prepared soot-based composite particles are facilely loaded on the porous skeleton of the sponge to obtain multifunctional superhydrophobic adsorbents. The reported superhydrophobic adsorbents exhibited robust chemical and mechanical stability, convenient magnetic collection, the high oil absorption capacity of 60-142 g g^-1, durable recyclability (>250 cycles), efficient separation efficiency (>99.5%) and outstanding self-heated performance, which enable them to be competent for oil-water separation in multitasking and complex environment (floating oils, continuous oil collection, oil-in-water emulsion, and viscous oil-spills).

Thermally treated candle soot as a novel catalyst for hydrogen peroxide in-situ production enhancement in the bio-electro-Fenton system

Thermally treated candle soot (TCS) was used as a two-electron (2e¯) oxygen reduction reaction (ORR) catalyst to in situ produce H₂O₂ in a bio-electro-Fenton (BEF) system. Compared with the pristine candle soot (CS), TCS showed larger Brunauer-Emmett-Teller (BET) surface area (102.54 m² g^-1 vs. 61.79 m² g^-1), higher mesoporous ratio (50.39% vs. 34.98%), and improved hydrophilicity. X-ray photoelectron spectra (XPS) results revealed that the C-O-C was the dominant oxygen-containing group of the CS, and its percentage reached at 80.55%. However, the C-O-C ratio of the TCS decreased to 48.93%, whilst it's CO and OC-O ratios significantly increased to 27.92% and 23.15%. The TCS showed a high H₂O₂ selectivity (87.5%∼97.0%) at the neutral pH condition, which was much higher than that of the commonly used carbon black (CB) catalyst. Finally, the H₂O₂ concentration maxima (C_max-_H2O2) of the bio-electro-Fenton system running with the TCS air-cathode (BEF-TCS) achieved at 32.02 mg/L, which was 6.29 times higher than that of the BEF-CB (5.09 mg/L). The removal and mineralization ratios of the SMX in the BEF-TCS reached at 83.0% and 79.0%, respectively. This paper reported a novel 2e¯ ORR electro-catalyst which was low-cost, easily available and highly efficiency.

Diiron azadithiolate clusters supported on carbon nanotubes for efficient electrocatalytic proton reduction

The first example of diiron azadithiolate clusters supported on carbon nanotubes (1-f-SWCNTs) was constructed via covalent attachment. This nanohybrid shows efficient electrocatalytic proton reduction with a TOF of 9444 s⁻¹ in 0.2 N aqueous H₂SO₄.

The in situ preparation of iron phosphide using ionic liquids as iron and phosphorus sources for efficient hydrogen evolution reactions

Ionic liquids (ILs) were utilized as iron and phosphorus sources for the preparation of iron phosphide for the first time. The IL trihexyl(tetradecyl)phosphonium tetrachloroferrate ([P(C6H13)3C14H29][FeCl4]) and carbon nanotubes (CNTs) were applied as precursors for the in situ preparation of Fe2P(IL6)/CNTs. This material has good catalytic activity and stability for the hydrogen evolution reaction, including a low onset overpotential (75 mV) and Tafel slope (68 mV dec-1). Moreover, this catalyst exhibits current densities of 10 and 20 mA cm-2 at overpotentials of 115 and 150 mV, respectively. The phosphidation process using [P(C6H13)3C14H29][FeCl4] was also investigated. All experimental results indicate that Fe2P can be formed in situ on the CNTs using this IL, and that the CNTs help the formation of the Fe2P nanoparticles and improve the electrical conductivity. This IL-based in situ preparation strategy is facile and environmentally friendly and does not require the addition of other reagents. This method holds great promise for application in other electrochemical studies.

Cobalt doping of FePS3 promotes intrinsic active sites for the efficient hydrogen evolution reaction

Exploring Earth-abundant electrocatalysts to achieve the efficient hydrogen evolution reaction (HER) is important for the development of clean and renewable hydrogen energy. Herein, we focus on a representative transition metal phosphosulfide electrocatalyst FePS3. Enlightened by our theoretical calculations that Co dopants improve H affinity on P sites and electrical conductivity, we prepared a series of Fe1-xCoxPS3 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25) compounds and characterized them by XRD, ICP, XPS, Raman, SEM, TEM, EDS, and resistivity and electrochemical measurement. It is found that the overpotential can be reduced by 166 mV, and the Tafel slope drops from 170 mV dec-1 to 80 mV dec-1. This work provides new insights to optimize the electrocatalytic hydrogen evolution activity of related transition metal phosphosulfides.

Candle flame soot sizing by planar time-resolved laser-induced incandescence

Soot emissions from flaming combustion are relevant as a significant source of atmospheric pollution and as a source of nanomaterials. Candles are interesting targets for soot characterization studies since they burn complex fuels with a large number of carbon atoms, and yield stable and repeatable flames. We characterized the soot particle size distributions in a candle flame using the planar two-color time-resolved laser induced incandescence (2D-2C TiRe-LII) technique, which has been successfully applied to different combustion applications, but never before on a candle flame. Soot particles are heated with a planar laser sheet to temperatures above the normal flame temperatures. The incandescent soot particles emit thermal radiation, which decays over time when the particles cool down to the flame temperature. By analyzing the temporal decay of the incandescence signal, soot particle size distributions within the flame are obtained. Our results are consistent with previous works, and show that the outer edges of the flame are characterized by larger particles ([Formula: see text]), whereas smaller particles ([Formula: see text]) are found in the central regions. We also show that our effective temperature estimates have a maximum error of 100 K at early times, which decreases as the particles cool.

Stretchable and Robust Candle-Soot Nanoparticle-Polydimethylsiloxane Composite Films for Laser-Ultrasound Transmitters

Considerable attention has been devoted to the development of nanomaterial-based photoacoustic transmitters for ultrasound therapy and diagnosis applications. Here, we fabricate and characterize candle-soot nanoparticles (CSNPs) and polydimethylsiloxane (PDMS) composite-based photoacoustic transmitters, based on a solution process, not just to achieve high-frequency and high-amplitude pressure outputs, but also to develop physically stretchable ultrasound transmitters. Owing to its non-porous and non-agglomerative characteristics, the composite exhibits unique photo-thermal and mechanical properties. The output pressure amplitudes from CSNPs-PDMS composites were 20-26 dB stronger than those of Cr film, used as a reference. The proposed transmitters also offered a center frequency of 2.44-13.34 MHz and 6-dB bandwidths of 5.80-13.62 MHz. Importantly, we characterize the mechanical robustness of CSNPs-PDMS quantitatively, by measuring laser-damage thresholds, to evaluate the upper limit of laser energy that can be ultimately used as an input, i.e., proportional to the maximum-available pressure output. The transmitters could endure an input laser fluence of 54.3-108.6 mJ·cm^-2. This is 1.65-3.30 times higher than the Cr film, and is significantly higher than the values of other CSNPs-PDMS transmitters reported elsewhere (22-81 mJ·cm^-2). Moreover, we characterized the strain-dependent photoacoustic output of a stretchable nanocomposite film, obtained by delaminating it from the glass substrate. The transmitter could be elongated elastically up to a longitudinal strain of 0.59. Under this condition, it maintained a center frequency of 6.72-9.44 MHz, and 6-dB bandwidth ranges from 12.05 to 14.02 MHz. We believe that the stretchable CSNPs-PDMS composites would be useful in developing patch-type ultrasound devices conformally adhered on skin for diagnostic and therapeutic applications.

Two-dimensional bimetallic phosphide ultrathin nanosheets as non-noble electrocatalysts for a highly efficient oxygen evolution reaction

Highly efficient non-noble metal oxygen evolution reaction (OER) catalysts are urgently needed for the practical application of electrochemical energy technology. Herein, we report two-dimensional (2D) bimetallic phosphide (Co1-xFexP) ultrathin nanosheets as new OER catalysts. The two-dimensional (2D) morphology of the nanosheets and the synergistic effect between different transition-metal elements made contributions to the OER catalysis. By optimizing the doping ratio of the Fe atoms, the Co0.8Fe0.2P nanosheets showed the best OER performance with a small overpotential of 270 mV versus a rotating hydrogen electrode at a current density of 10 mA cm-2 and low Tafel slope of 50 mV dec-1 in an alkaline electrolyte. Moderate iron doping improved the degree of oxidation at the surface of CoP nanosheets and preserved the conductive and chemically stabilizing host, thereby enhancing the OER activity. Our findings could aid the rational design of novel non-layered 2D nanomaterial OER catalysts.

Candle Soot Carbon Nanoparticles in Photoacoustics: Advantages and Challenges for Laser Ultrasound Transmitters

This manuscript provides a review of candle-soot nanoparticle (CSNP) composite laser ultrasound transmitters (LUT), and compares and contrasts this technology to other carboncomposite designs. Among many carbon-based composite LUTs, a CSNP composite has shown its advantages of maximum energy conversion and fabrication simplicity for developing highly efficient ultrasound transmitters. This review focuses on the advantages and challenges of the CSNP-composite transmitter in the aspects of nanostructure design, fabrication procedure, and promising applications. Included are a brief description of the basic principles of the laser ultrasound transmitter, a review of general properties of CSNPs, as well as details on the fabrication method, photoacoustic performance, and design factors. A comparison of the CSNP-nanocomposite to other carbon-nanocomposites is provided. Lastly, representative applications of carbon-nanocomposite transmitters and future perspectives on CSNP-composite transmitters are presented.

Coupling Ultrafine Pt Nanocrystals over the Fe2P Surface as a Robust Catalyst for Alcohol Fuel Electro-Oxidation

Ultrafine Pt nanocrystals with an average particle size of 2.2 ± 1 nm coupled over the petaloid Fe₂P surface are proposed as a novel, efficient, and robust catalyst for alcohol fuel electro-oxidation. The strong coupling effect of metal-support imparts a strong electronic interaction between the Fe₂P and Pt interface that can weaken the adsorption of poisoning CO species according to the d-band theory. Defects and increased surface area of the petaloid Fe₂P are beneficial to the Pt nanoparticle anchoring and dispersion as well as the charge transfer and reactant transportation during the electrochemical reaction. These features make the Pt-Fe₂P catalyst system exhibit excellent catalytic activity, antipoisoning ability, and catalytic stability for alcohol fuel of methanol and ethanol electro-oxidation compared with a controlled Pt/C catalyst. The high catalytic efficiency is proposed to come from the strong coupling effect of Pt and petaloid Fe₂P interface that can maintain the mechanical and chemical stability of the catalyst system. This kind of phosphide-supported ultrafine Pt nanocrystals will be a promising catalyst in fuel cells.

Water-Dispersible Candle Soot-Derived Carbon Nano-Onion Clusters for Imaging-Guided Photothermal Cancer Therapy

Herein, water-dispersible carbon nano-onion clusters (CNOCs) with an average hydrodynamic size of ≈90 nm are prepared by simply sonicating candle soot in a mixture of oxidizing acid. The obtained CNOCs have high photothermal conversion efficiency (57.5%), excellent aqueous dispersibility (stable in water for more than a year without precipitation), and benign biocompatibility. After polyethylenimine (PEI) and poly(ethylene glycol) (PEG) modification, the resultant CNOCs-PEI-PEG have a high photothermal conversion efficiency (56.5%), and can realize after-wash photothermal cancer cell ablation due to their ultrahigh cellular uptake (21.3 pg/cell), which is highly beneficial for the selective ablation of cancer cells via light-triggered intracellular heat generation. More interestingly, the cellular uptake of CNOCs-PEI-PEG is so high that the internalized nanoagents can be directly observed under a microscope without fluorescent labeling. Besides, in vivo experiments reveal that CNOCs-PEI-PEG can be used for photothermal/photoacoustic dual-modal imaging-guided photothermal therapy after intravenous administration. Furthermore, CNOCs-PEI-PEG can be efficiently cleared from the mouse body within a week, ensuring their excellent long-term biosafety. To the best of the authors' knowledge, the first example of using candle soot as raw material to prepare water-dispersible onion-like carbon nanomaterials for cancer theranostics is represented herein.

In situ synthesis of FeP-decorated Ti–Fe2O3: an effective strategy to improve the interfacial charge transfer in the photoelectrochemical water oxidation reaction

The unprecedented FeP/Ti–Fe₂O₃ possesses the advantages of efficient charge transfer in the bulk photoanode and at the interface of the photoanode and the electrolyte.

Ferric phosphide carbon nanocomposites emerging as highly active electrocatalysts for the hydrogen evolution reaction

This Frontier article highlights the recent development and advances in designing ferric phosphide (FeP) based composite materials for the HER.

Cost-Effective Alkaline Water Electrolysis Based on Nitrogen- and Phosphorus-Doped Self-Supportive Electrocatalysts

Water splitting into hydrogen and oxygen in order to store light or electric energy requires efficient electrocatalysts for practical application. Cost-effectiveness, abundance, and efficiency are the major challenges of the electrocatalysts. Herein, this paper reports the use of low-cost 304-type stainless steel mesh as suitable electrocatalysts for splitting of water. The commercial and self-support stainless steel mesh is subjected to exfoliation and heteroatom doping processes. The modified stainless steel electrocatalyst displays higher oxygen evolution reaction property than the commercial IrO₂ , and comparable hydrogen evolution reaction property with that of Pt. More importantly, an all-stainless-steel-based alkaline electrolyzer (denoted as NESSP//NESS) is designed for the first time, which possesses outstanding stability along with lower overall voltage than the conventional Pt//IrO₂ electrolyzer at increasing current densities. The remarkable electrocatalytic properties of the stainless steel electrode can be attributed to the unique exfoliated-surface morphology, heteroatom doping, and synergistic effect from the uniform distribution of the interconnected elemental compositions. This work creates prospects to the utilization of low-cost, highly active, and ultradurable electrocatalysts for electrochemical energy conversion.

3D ordered porous MoxC (x = 1 or 2) for advanced hydrogen evolution and Li storage

3D ordered porous structures of Mo_xC are prepared with different Mo to C ratios and tested for two possible promising applications: hydrogen evolution reaction (HER) through water splitting and lithium ion batteries (LIBs). Mo₂C and MoC with 3D periodic ordered structures are prepared with a similar process but different precursors. The 3D ordered porous MoC exhibits excellent cycling stability and rate performance as an anode material for LIBs. A discharge capacity of 450.9 mA h g^-1 is maintained up to 3000 cycles at 10.0 A g^-1. The Mo₂C with a similar ordered porous structure shows impressive electrocatalytic activity for the HER in neutral, alkaline and acidic pH solutions. In particular, Mo₂C shows an onset potential of only 33 mV versus a reversible hydrogen electrode (RHE) and a Tafel slope of 42.5 mV dec^-1 in a neutral aqueous solution (1.0 M phosphate buffer solution), which is approaching that of the commercial Pt/C catalyst.

Large-Scale Synthesis of Carbon-Shell-Coated FeP Nanoparticles for Robust Hydrogen Evolution Reaction Electrocatalyst

A highly active and stable non-Pt electrocatalyst for hydrogen production has been pursued for a long time as an inexpensive alternative to Pt-based catalysts. Herein, we report a simple and effective approach to prepare high-performance iron phosphide (FeP) nanoparticle electrocatalysts using iron oxide nanoparticles as a precursor. A single-step heating procedure of polydopamine-coated iron oxide nanoparticles leads to both carbonization of polydopamine coating to the carbon shell and phosphidation of iron oxide to FeP, simultaneously. Carbon-shell-coated FeP nanoparticles show a low overpotential of 71 mV at 10 mA cm^-2, which is comparable to that of a commercial Pt catalyst, and remarkable long-term durability under acidic conditions for up to 10 000 cycles with negligible activity loss. The effect of carbon shell protection was investigated both theoretically and experimentally. A density functional theory reveals that deterioration of catalytic activity of FeP is caused by surface oxidation. Extended X-ray absorption fine structure analysis combined with electrochemical test shows that carbon shell coating prevents FeP nanoparticles from oxidation, making them highly stable under hydrogen evolution reaction operation conditions. Furthermore, we demonstrate that our synthetic method is suitable for mass production, which is highly desirable for large-scale hydrogen production.

Non-Noble Metal-based Carbon Composites in Hydrogen Evolution Reaction: Fundamentals to Applications

Hydrogen has been hailed as a clean and sustainable alternative to finite fossil fuels in many energy systems. Water splitting is an important method for hydrogen production in high purity and large quantities. To accelerate the hydrogen evolution reaction (HER) rate, it is highly necessary to develop high efficiency catalysts and to select a proper electrolyte. Herein, the performances of non-noble metal-based carbon composites under various pH values (acid, alkaline and neutral media) for HER in terms of catalyst synthesis, structure and molecular design are systematically discussed. A detailed analysis of the structure-activity-pH correlations in the HER process gives an insight on the origin of the pH-dependence for HER, and provide guidance for future HER mechanism studies on non-noble metal-based carbon composites. Furthermore, this Review gives a fresh impetus to rational design of high-performance noble-metal-free composites catalysts and guide researchers to employ the established electrocatalysts in proper water electrolysis technologies.

Strong Metal-Phosphide Interactions in Core-Shell Geometry for Enhanced Electrocatalysis

Rational design of multicomponent material structures with strong interfacial interactions enabling enhanced electrocatalysis represents an attractive but underdeveloped paradigm for creating better catalysts for important electrochemical energy conversion reactions. In this work, we report metal-phosphide core-shell nanostructures as a new model electrocatalyst material system where the surface electronic states of the shell phosphide and its interactions with reaction intermediates can be effectively influenced by the core metal to achieve higher catalytic activity. The strategy is demonstrated by the design and synthesis of iron-iron phosphide (Fe@FeP) core-shell nanoparticles on carbon nanotubes (CNTs) where we find that the electronic interactions between the metal and the phosphide components increase the binding strength of hydrogen adatoms toward the optimum. As a consequence, the Fe@FeP/CNT material exhibits exceptional catalytic activity for the hydrogen evolution reaction, only requiring overpotentials of 53-110 mV to reach catalytic current densities of 10-100 mA cm^-2.

FeP and FeP2nanowires for efficient electrocatalytic hydrogen evolution reaction

FeP and FeP₂nanowires exhibit excellent electrocatalytic abilities toward hydrogen evolution from water splitting.

Facile synthesis of iron phosphide nanorods for efficient and durable electrochemical oxygen evolution

Iron phosphide (FeP) nanorods supported on carbon fiber paper electrodes exhibit outstanding electrocatalytic activity and long-term stability toward the oxygen evolution reaction.

High-efficiency hydrogen evolution reaction catalyzed by iron phosphide nanocrystals

Iron phosphide ultrafine nanocrystals supported on carbon black were synthesized via a facile method and used as a highly efficient hydrogen evolution reaction electrocatalyst.

Synthesis of MoP decorated carbon cloth as a binder-free electrode for hydrogen evolution

Electrocatalysts play a vital role in electrochemical water-splitting for hydrogen production.