Metallic Co,CoS, and P co-doped N enriched carbon derived from ZIF-67 as an efficient catalyst for hydrogen evolution reaction

Exploring non-precious materials with efficient electrocatalytic performance to replace the precious Pt-based materials for hydrogen evolution reaction (HER) is still a great challenge now. Herein, metallic Co, CoS, and P co-doped N enriched carbon (CoSP/NC) was successfully fabricated by using ZIF-67 as precursor via a facile pyrolysis, sulphurization, and phosphorization process for HER application. ZIF-67 was transformed into metallic Co doped N enriched carbon (Co/NC) undergoing the treatment of high temperature. After being sulphurized, part of metallic Co was transformed into CoS and attached firmly on the surface of the catalyst. P element was well dispersed on the catalyst during the phosphorization process. The fabricated CoSP/NC exhibits the optimal HER activity with the superior overpotential of 183 mV at 10 mA cm⁻² and the lowest Tafel slope of 64.25 mV dec⁻¹. Furthermore, CoSP/NC shows superior durability. The excellent HER performance may be ascribed to the abundant active sites, firm structure, and superior electrical conductivity of the carbon. Thus, this work provides a new strategy to fabricate non-precious materials with excellent HER performance for the following researchers.     

ZnS,Fe, and P co-doped N enriched carbon derived from MOFs as efficient electrocatalyst for oxygen reduction reaction

Exploring electrocatalysts with low cost and excellent performance for oxygen reduction reaction is still a significant challenge. In this paper, we introduce a novel strategy to fabricate ZnS, Fe, and P co-doped N enriched carbon (ZnFeSP/NC) via the direct carbonization of PVP/ZIF-8 combined with absorption, sulphurization, and phosphorization processes. The as-synthesized ZnFeSP/NC was used as electrocatalyst for oxygen reduction reaction (ORR). We explored the influence of Fe, S, and P elements on the ORR activity of the catalysts. It can be found that ZnS nanoparticles were formed and attached on the surface of the ZnFeSP/NC nanoparticles. α-Fe and P element were well dispersed on ZnFeSP/NC nanoparticles. Fe, S, and P element can highly enhance the ORR activity of the catalysts. Compared to Zn/NC, ZnFe/NC, and ZnFeS/CN, ZnFeSP/NC shows the optimal ORR performance with the half-wave potential of 0.859 V and a current density of 3.33 mA cm⁻² at −0.85 V. Furthermore, ZnFeSP/NC also exhibits excellent long-term operation stability, effectively avoiding any ORR performance decay.     

MOF-derived Zn,S, and P co-doped nitrogen-enriched carbon as an efficient electrocatalyst for hydrogen evolution reaction

In this study, Zn, S, and P co-doped nitrogen N-enriched carbon (ZnSP/NC) was successfully fabricated as an efficient electrocatalyst for the hydrogen evolution reaction (HER) process via pyrolysis, sulfurization, and phosphorization. The metal Zn derived from zeolitic imidazolate framework-8 (ZIF-8) was combined with the S element to form ZnS nanoparticles, and then embedded in N-enriched carbon during the sulfurization process. Following this, the P element was well-dispersed in the catalyst via phosphorization. It was found that ZnSP/NC exhibits excellent electrocatalytic activity when used as a catalyst for the HER process. ZnSP/NC, with an overpotential of 171 mV and a Tafel slope of 54.78 mV dec⁻¹, demonstrates superior electrocatalytic activity as compared to Zn/NC (277 mV, 92.34 mV dec⁻¹) and ZnS/NC (241 mV, 76.41 mV dec⁻¹). During the HER process, ZnS and P serve as active sites, while the N-enriched carbon provides reliable electronic transmission. The synergistic effects among the ZnS, P, and N-enriched carbon result in an excellent electrocatalytic activity of ZnSP/NC for the HER process.     

One-step complexation and self-template strategy to synthesis bimetal Fe/Mn–N doped interconnected hierarchical porous carbon for enhancing catalytic oxygen reduction reaction

Currently, it is still a challenge in the research of fuel cells and zinc-air battery to use a facile method to prepare efficient and low-cost cathode oxygen reduction reaction (ORR) catalysts to replace the precious metal Pt-based catalyst. Herein, we reported a one-step complexation of ethylenediaminetetraacetic acid disodium (EDTA-2Na) with transition metals (M) and self-template strategy to synthesis an bimetal Fe/Mn–N doped interconnected hierarchical porous carbon material for efficient catalytic ORR. In addition to being a carbon source, EDTA-2Na can very well fix M atoms in the carbon precursory by complexation, which is beneficial for M atoms to be anchored in the carbon structure by N atoms, thus forming the M-N_x catalytic active site. During pyrolysis, meanwhile, Na ions in EDTA-2Na not only acted as self-template to form the interconnected porous structure but also separated M atoms from each other, which also suppressed the aggregation and growth of the M atoms. More importantly, the prepared bimetal Fe/Mn–N doped interconnected hierarchical porous carbon (Fe/Mn–NIHPC) showed better catalytic ORR performance (half-wave potentials of 0.86 V vs. RHE) than those prepared by single metal elements (Fe or Mn). And Fe/Mn–NIHPC also exhibited better catalytic ORR activity and durability, compared with the Pt/C (20 wt%) catalyst.     

Zn,S, N self-doped carbon material derived from waste tires for electrocatalytic hydrogen evolution

Developing multielement doped carbon material (CM) is extremely meaningful due to the synergistic regulation on electronic and molecular structure, which can endow catalysts with high electrochemical properties. However, it is a challenging issue owing to the complex and difficult preparation process. Herein, a novel waste tires-derived Zn, S, N self-doped CM is prepared and used for efficiently electrocatalytic hydrogen evolution reaction (HER). The electronic state and molecular structure are effectively adjusted by forming C–N and C–S bonds in CM, and the Zn 3d configuration could participate in molecular orbital hybridization to produce the synergistic effect with regulation of N and S, thus improving the electrocatalytic HER activity. The obtained Zn, S, N self-doped CM requires only an overpotential of 50 mV at 10 mA cm^?2, which is close to that of Pt/C (42 mV). The cell voltage of Zn, S, N self-doped CM || RuO₂ electrolyze (1.31 V) at 10 mA cm^?2 is much smaller than that of Pt/C || RuO₂ (1.46 V). This work points out a promising strategy for the development of multielement doped CM applied in electrocatalytic HER and the efficiently resourceful utilization of waste tires.     

Nitrogen,sulfur, and oxygen tri-doped carbon nanosheets as efficient multifunctional electrocatalysts for Zn-air batteries and water splitting

Nitrogen, sulfur, and oxygen tri-doped carbon nanosheets (N, S, O-CNs) were prepared by a modified in-situ g-C₃N₄ template method with a plant-waste, rice straw, as the carbon precursor. The N, S, O-CNs could worked as efficient electrocatalysts for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). Significantly, the introduced S element can particularly activate the electron transfer and accelerate reaction kinetics for HER, while the N/O dopants can efficiently promote the ORR and OER. As a result, the N, S, O-CNs exhibited excellent performance with favorable kinetics and decent durability as a multifunctional ORR, OER and HER catalyst. Moreover, the rechargeable liquid/solid Zn−air battery and water splitting device showed superior performance by assembling this N, S, O-CNs catalyst. This work paves a universal avenue towards further development of plant-waste derived carbon materials with heteroatom dopants as the highly efficient electrocatalysts in energy devices.     

Fe,N codoped porous carbon nanosheets for efficient oxygen reduction reaction in alkaline and acidic media

Electrospinning typically employed to fabricate nanofibers was first used to prepare Fe and N doped porous carbon nanosheets (Fe–N/CNs) as oxygen reduction reaction (ORR) electrocatalysts. Polyacrylonitrile nanofibers containing a small amount of ferrocenes (Fer-PAN) were produced by electrospinning. When Fer-PAN was preoxidized at 300 °C in the air (Fer-PAN-300), nanosheets were formed and occupied the interspace between nanofibers. Fe–N/CNs was finally obtained using carbonized Fer-PAN-300 at 900 °C in N₂. The Fe–N/CNs incorporated the advantages of carbon nanofiber webs and porous nanocarbon materials, inclusive of comparatively high conductivity and large specific surface area. In both alkaline and acidic electrolyte, the Fe–N/CNs took on similar even better ORR catalytic activity than other catalysts reported elsewhere, and better stability than those of commercial Pt/C.     

Facile preparation of N,P co-doped molybdenum carbide / porous carbon rough microspheres for efficient electrocatalytic hydrogen evolution

Despite that diverse carbon materials have been designed as framework to anchor molybdenum carbide to efficiently improve catalytic performance for hydrogen evolution reaction (HER), simply and uniformly hybridizing Mo and carbon source to form well-defined heteroatom-doped Mo₂C/carbon nanostructure using suitable precursors to expose the more active sites and optimize electron structure Mo₂C is still great challenge. Herein, we design and fabricate N, P-co-doped molybdenum carbide/porous carbon hybrid rough microspheres by a simple hydrothermal and followed annealing method using red jujube and phosphomolybdic acid as carbon and Mo source, respectively. Benefiting from carbon framework derived from red jujube inhibiting the aggregation of Mo₂C nanoparticles, N, P co-doping changing the electro-structure of the adjacent Mo and C atoms, and rough micro-spherical structure increasing the electrolyte-active materials contact surface, the resulting material exhibits high electrocatalytic performance with a low overpotential of 103 and 80 mV at current densities of 10 mA cm⁻², a small Tafel slope of 57 and 46 mV dec⁻¹, respectively, in acidic and alkaline electrolyte, and excellent stability. The convenient resource, facile preparation and high performance make this material showing great potential in cost effective hydrogen production.     

Nitrogen doped porous carbon with iron promotion for oxygen reduction reaction in alkaline and acidic media

Nitrogen doped water-hyacinth graphite with little iron (NFe-WHG) is synthesized by using water hyacinth as carbon source, dopamine hydrochloride as N source and Fe(NO₃)₃ as Fe source. The water hyacinth is carbonized to porous carbon; the addition of Fe increases pore diameter, graphitization degree, total N and pyridinic N content. The characterizations indicate that the doping N contributes great on ORR activity, yet the residual Fe species themselves show inconspicuous catalytic effect on ORR. The NFe-WHG with the above features displays superior ORR activity in alkaline media and comparable ORR activity to commercial Pt/C in acidic media. Due to the graphite matrix and that most of the Fe species have been removed, the NFe-WHG shows excellent stability in both alkaline and acidic media with excellent anti-methanol and anti-CO performances.     

Atomic metal,N, S co-doped 3D porous nano-carbons: Highly efficient catalysts for HT-PEMFC

A new strategy for fabricating atomically dispersed heteroatom-doped nanoporous carbon materials is reported. Through the self-assembly of dopamine, triblock copolymer F127, and metal ions, different three-dimensional atomic metal-N/S doped carbon catalysts are obtained after pyrolysis. Noble metal salts with ferrous sulfate induce the bimetallic monatomic FeM (M = Pd, Pt) N, S-doped carbon catalysts. Minute amounts of Pt or Pd single atoms in the catalysts greatly improve the oxygen reduction reaction (ORR) activity both in acidic and alkaline conditions. Typically, the obtained Fe, Pt–N/S co-doped carbon (FePt-NSC) catalyst exhibits superior ORR performance with positive half-wave potentials (E_1/2) of 0.89 and 0.80 V in alkaline and acidic solutions, respectively. In addition, FePt-NSC displays dominant four electron catalytic process and excellent electrocatalytic stability. The high temperature proton exchange membrane fuel cell (HT-PEMFC) test (160 °C) illustrates that FePt-NSC reaches 0.67 V at 400 mA/cm² and achieves the peak power density of 628 mW/cm², better than most of the catalysts reported at the similar conditions. These results indicate the atomic metal-N/S doped porous carbon catalysts to be highly promising low-Pt catalysts for HT-PEMFC.     

Hydrogen evolution reaction on in-plane platinum and palladium dichalcogenides via single-atom doping

Searching for the catalysts with excellent catalytic activity and high chemical stability is the key to achieve large-scale production of hydrogen (H₂) through hydrogen evolution reaction (HER). Two-dimensional (2D) platinum and palladium dichalcogenides with extraordinary electrical properties have emerged as the potential candidate for HER catalysts. Here, chemical stability, HER electrocatalytic activity, and the origin of improved HER performance of Pt/Pd-based dichalcogenides with single-atom doping (B, C, N, P, Au, Ag, Cu, Co, Fe, Ni, Zn) and vacancies are explored by first-principles calculations. The calculated defect formation energy reveals that most defective structures are thermodynamically stable. Hydrogen evolution performance on basal plane is obviously improved by single-atoms doping and vacancies. Particularly, Zn-doped and Te vacancy PtTe₂ have a ΔG_H value close to zero. Moreover, defect engineering displays a different performance on HER catalytic activity in sulfur group elements, in order of S < Te < Se in Pd-based chalcogenides, and S < Se < Te in Pt-based chalcogenides. The origin of improved hydrogen evolution performance is revealed by electronic structure and charge transfer. Our findings of the highly activating defective systems provide a theoretical basis for HER applications of platinum and palladium dichalcogenides.     

Manganese coordinated with nitrogen in aligned hierarchical porous carbon for efficient electrocatalytic oxygen reduction reaction in alkaline and acidic medium

A Mn coordinated with N atoms aligned hierarchical porous carbon catalyst is prepared through an inorganic metal salt sublimation doping strategy. Gelatin is served as a carbon source and N source, Ca²⁺ is acted as templates to establish aligned porous structure during carbonization. MnCl₂ sublimates into gas to serve as Mn source after reaching the melting point. This method can effectively avoid the agglomeration of Mn atoms, which is beneficial to form Mn-N_x active sites. The prepared optimal catalyst exhibits a large specific surface area with an aligned hierarchical porous structure. XAFs result demonstrates that Mn coordinates with N atoms to form Mn-N_x configuration in the carbon structure. Notably, it exhibits outstanding catalytic ORR performance with a positive half-wave potential (0.86 V vs. RHE) and excellent durability, superior to Pt/C (20 wt%) catalyst under alkaline medium. Meanwhile, enhanced catalytic ORR performance and stability in an acidic medium are also achieved.     

Inorganic doped libethenite nanoparticle clusters show high catalytic activity in hydrogen evolution reaction

A noble metal-free Na Al Si doped libethenite nanoparticle clusters were obtained by applying the method of hydrothermal synthesis. The Linear Sweep Voltammetry (LSV) curve of this nanoparticle cluster electrode shows that there is no noble metal in the hydrogen evolution reaction (HER), and it still exhibits good catalytic activity. The catalytic activity of the libethenite nanoparticle cluster is further enhanced after reduction by the amperometric i-t curve method (A i-t C). The electrochemical performance and catalytic mechanism were investigated by the cyclic voltammetry (CV) method. The characterization analysis by XRD, SEM, TEM, EDS, and XPS found that the catalyst was isomorphous with the natural mineral libethenite, but different from the minerals with Cu and P as the main components in nature when the crystal synthesized under hydrothermal conditions was doped. The heterogenous libethenite nanoparticle cluster framework is replaced by more additional Na, Al, and Si elements. Cu and P elements in the libethenite nanoparticle cluster structure are connected through the mineral framework and uniformly distributed in the crystal structure. This structure increases the electrochemical activity of its HER. Due to the interaction of Cu and P, the catalyst exhibits good catalytic performance for HER under acidic conditions. The reduction by the electrochemical i-t curve reduces the consumption of Cu and enhances the stability of the mineral framework.     

N,P-co-doped carbon coupled with CoP as superior electrocatalysts for hydrogen evolution reaction and overall water splitting

To achieve high activity and stability for both hydrogen and oxygen evolution reactions through the non-precious-metal based electrocatalysts is still facing the great challenge. Herein, we demonstrate a facile strategy to prepare CoP nanoparticles (NPs) loaded on N, P dual-doped carbon (NPC) electrocatalysts with high concentration N and P dopants through a pyrolysis-deposition-phosphidation process. The great bifunctional electrocatalytic activity for both HER (the overpotential of 98 mV and 86 mV at 10 mA cm⁻² in both 0.5 M H₂SO₄ and 1 M KOH electrolytes, respectively) and OER (the overpotential of 300 mV at 10  mA cm⁻² in 1 M KOH electrolyte) were achieved. When CoP@NPC hybrid was used as two electrodes in the 1 M KOH electrolyte system for overall water splitting, the needed cell potential for achieving the current density of 10 mA cm⁻² is 1.6 V, and it also showed superior stability for HER and OER after 10 h’ test with almost negligible decay. Experimental results revealed that the P atoms in CoP were the active sites for HER and the CoP@NPC hybrid showed excellent bifunctional electrocatalytic properties due to the synergistic effects between the high catalytic activity of CoP NPs and NPC, in which the doping of N and P in carbon led to a stronger polarization between Co and P in CoP, promoting the charge transfer from Co to P in CoP, enhancing the catalytic activity of P sites and Co sites in CoP for HER and OER, respectively. Specifically, the improvements could result from the changed charge state, the increased active specific surface area, and the facilitated reaction kinetics by N, P co-doping and admixture. This work provides a high-efficient, low-cost and stable electrocatalyst for overall water splitting, and throws light on rational designing high performance electrocatalysts.     

Nitrogen doped lotus stem carbon as electrocatalyst comparable to Pt/C for oxygen reduction reaction in alkaline media

The nitrogen doped carbon with high content of pyridine N and porous structure indicates high activity for oxygen reduction reaction (ORR). In this paper, nitrogen doped lotus stem carbon (N-LSC) with 6.3 at% of N (containing 52 at% of pyridine N) and porous structure is developed by using lotus stem as carbon source and dopamine hydrochloride as nitrogen source. The ORR activity, stability and methanol tolerance are characterized. The results show that the N-LSC has comparable activity to Pt/C, and much better methanol tolerance and stability than Pt/C. The porous structure and high content of pyridine N are believed to lead to the high ORR performances of the N-LSC.     

Synthesis of Ni2P/Ni5P4 on porous N decorated rGO foam for efficiently electrocatalytic hydrogen evolution reaction

As a new generation of non-precious metal catalysts, nickel phosphide is regarded as an ideal substitute for precious metal platinum in electrochemical hydrogen evolution. Here, a hydrogen evolution reaction (HER) electrocatalyst is developed by in situ growth of Ni₂P/Ni₅P₄ heterostructures on porous N decorated rGO foam (named Ni₂P/Ni₅P₄/N-rGO). The porous rGO foam structure provides a larger surface area and abundant active sites. The Ni₂P/Ni₅P₄ nanoparticles with heterostructures are uniformly distributed on the rGO sheet, which enhance the charge transfer ability. The decorating of N element also correspondingly improves the HER performance. The as-prepared Ni₂P/Ni₅P₄/N-rGO exhibits excellent HER performance in alkaline medium. When the current density is 10 mA cm^?2, the overpotential is only 22 mV. No obvious loss of HER activity after 2000 cyclic voltammetry indicates that the composite has excellent stability. This work presents a valuable route for fabricating inexpensive and high-performance catalysts for electrocatalysis.     

Facile synthesis of Ni5P4 nanosheets/nanoparticles for highly active and durable hydrogen evolution

It is essential to search highly active, steady and cheap non-noble electrocatalyst for hydrogen evolution reaction (HER). At present, nickel phosphides are extensively used in electrochemical hydrogen evolution due to its excellent stability and activity. Hence, we report a facile, effective and feasible strategy to synthesis of Ni₅P₄ nanosheets/nanoparticles structure on carbon cloth, which was fabricated by electroless nickel plating on carbon cloth followed via straightforward thermal phosphidation treatment with NaH₂PO₂ as phosphorus source. The as-prepared CC@Ni–P electrocatalyst exhibits HER activity with low overpotentials (93 mV vs. RHE) to attain current density 10 mA/cm² as well as small Tafel slope (58.2 mV/dec), which outperforms most nickel phosphides electrocatalysts. The excellent HER performance can be ascribed to the large electrochemically active surface area, and phosphorus-rich Ni₅P₄ phase can supply further bridges sites of Ni and P. Significantly, as-prepared CC@Ni–P catalyst electrode exhibits no apparent HER activity decay after continuous stability test. Beyond that, the approach can be readily used to fabricate large size (5 × 5 cm) nickel phosphide electrocatalyst with excellent HER performance, which may be conducive to the proton exchange membrane (PEM) water electrolyser applications in future. This work opens an effective way to construct excellent performance transition-metal phosphides for HER.     

Controllable synthesized CoP-MP (M=Fe,Mn) as efficient and stable electrocatalyst for hydrogen evolution reaction at all pH values

The introduction of metal atom or heteroatom into transition metal phosphide is an effective strategy to enhance the electrochemical activity for hydrogen evolution reaction, while the controllable synthesis and purposeful design of efficient and stable transition metal phosphide based electrocatalyst with typical structural morphology is still a big challenge. Here, we investigated the relationship among the variety of the doped metal element (Fe and Mn), the corresponding morphology and electrocatalytic performance of the obtained sample for hydrogen evolution reaction. We found that with the doping of Fe and Mn, the cylinder-like CoP has transformed into microflower-like CoP-FeP and rambutan-like CoP-MnP, respectively. Meanwhile, the obtained CoP-FeP exhibits the excellent electrocatalytic activity hydrogen evolution reaction (HER) over a wide pH range (0–14), followed by CoP-MnP and CoP, resulting from the typical nanostructure and the moderately optimized electronic structure of P and Co center.     

Facile synthesis of the encapsulation of Co-based multimetallic alloys/oxide nanoparticles nirtogen-doped carbon nanotubes as electrocatalysts for the HER/OER

The pivotal challenge of electrocatalysis remains the development of highly effective electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). In this work, a universal strategy of preparing the encapsulation of Co-based multimetallic alloys/oxide nanoparticles in nitrogen-doped carbon nanotubes (named CoM@CNTs, M = Ni/Mn/Fe) was induced by annealing mixtures of the as-synthesized precursor, ethanol and different metallic acetates, including binary CoNi@CNTs, ternary CoNi/MnO@CNTs and quaternary CoNiFe/MnO@CNTs. By virtue of its unique structure with a high electrical conductive network based on CNT substrates, abundant catalytic active sites supplied by multimetallic nanoparticles and protection against nanoparticle corrosion by N-doped carbon layers, the as-synthesized CoNiFe/MnO@CNTs electrocatalyst has remarkable HER properties with a low overpotential of 122 mV and OER activity with a low overpotential of 275 mV at 10 mA cm^?2 and excellent stability and durability under long-term testing in alkaline solutions. Therefore, this strategy will provide a new route for fabricating multimetallic-based CNTs as HER/OER electrocatalysts with excellent stability and high catalytic activity.     

One-step synthesis of Co2P/N-P co-doped porous carbon composites derived from soybean derivatives as acidic and alkaline HER electrocatalysts

Developing inexpensive and efficient electrocatalysts for hydrogen evolution reaction (HER) in both acidic and alkaline mediums is of great significance to the hydrogen energy industry. Hereby, we prepared a mixture of precursors with homogeneous composition by using the chelating ability of soybean protein isolate (C and N source) and phytic acid (dopant and phosphating agent) with cobalt ions, and achieved one-step synthesis and construction of Co₂P/N–P co-doped porous carbon composite by carbonization at 800 °C. The as-synthesized Co₂P/NPPC-800 electrocatalyst exhibits low HER overpotentials of 121 and 125 mV at 10 mA cm^?2 in 0.5 M H₂SO₄ and 1.0 M KOH, which are close to those of the commercial Pt/C catalyst. Additionally, the NPPC substrate surrounding the Co₂P could diminish the corrosion during the HER, and Co₂P/NPPC-800 displays good stability and durability. Furthermore, this work offers a convenient synthesis strategy for phosphide/doped porous carbon composites in other electrochemical energy technologies.