Dysprosium doped copper oxide (Cu1-xDyxO) nanoparticles enabled bifunctional electrode for overall water splitting

The production of hydrogen, a favourable alternative to an unsustainable fossil fuel remains as a significant hurdle with the pertaining challenge in the design of proficient, highly productive and sustainable electrocatalyst for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, the dysprosium (Dy) doped copper oxide (Cu_1-xDy_xO) nanoparticles were synthesized via solution combustion technique and utilized as a non-noble metal based bi-functional electrocatalyst for overall water splitting. Due to the improved surface to volume ratio and conductivity, the optimized Cu_1-xDy_xO (x = 0.01, 0.02) electrocatalysts exhibited impressive HER and OER performance respectively in 1 M KOH delivering a current density of 10 mAcm^?2 at a potential of ?0.18 V vs RHE for HER and 1.53 V vs RHE for OER. Moreover, the Dy doped CuO electrocatalyst used as a bi-functional catalyst for overall water splitting achieved a potential of 1.56 V at a current density 10 mAcm^?2 and relatively high current density of 66 mAcm^?2 at a peak potential of 2 V. A long term stability of 24 h was achieved for a cell voltage of 2.2 V at a constant current density of 30 mAcm^?2 with only 10% of the initial current loss. This showcases the accumulative opportunity of dysprosium as a dopant in CuO nanoparticles for fabricating a highly effective and low-cost bi-functional electrocatalyst for overall water splitting.     

A novel in-situ strategy develops for Mo2C nanoparticles incorporated on N,P co-doped stereotaxically carbon as efficient electrocatalyst for overall water splitting

Developing cost-effective and remarkable electrocatalysts toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performs excelling role in boosting the hydrogen energy application. Herein, a novel in-situ one-pot strategy is developed for the first time to synthesize molybdenum carbide nanoparticles (Mo₂C NPs) incorporated on nitrogen (N) and phosphorous (P) co-doped stereotaxically carbon (SC). The optimized Mo₂C NPs/N, P–SC–800 electrocatalyst exhibits lower overpotentials of 131 and 287 mV for HER and OER to deliver a current density of 10 mA cm^?2 in 1.0 M KOH medium with smaller Tafel slopes of 58.9 and 74.4 mV/dec, respectively. In addition, an electrolyzer using Mo₂C NPs/N, P–SC–800 electrode as cathode and anode delivers a current density of 10 mA cm^?2 at a small voltage of 1.64 V for overall water splitting. The excellent water splitting performance could be ascribed to optimum Mo₂C NPs for more accessible active sites, highly active N, P-SC networks for accelerated electron transfers, and synergetic effect between Mo₂C NPs and N, P-SC networks. The N, P-SC network not only enhances the overall dispersion of Mo₂C NPs but also contributes numerous electroactive edges to enhance the performance of HER, OER, and overall water splitting activity. This research work explores the in-situ one-step strategies of advanced, cost-effective, and non-precious metal electrocatalysts for efficient water splitting and motivates the consideration of a novel class of heteroatom doped stereotaxically carbon nanocomposites for sustainable energy production.     

Enhancement in the catalytic activity of two-dimensional α-CN by B,Si and P doping for hydrogen evolution and oxygen evolution reactions

Employing the Density Functional Theory investigations, we have designed 2D α-CN with the dopants P, Si and B as catalyst for HER and OER activities. Doping of P and B over α-CN modifies its electronic properties and reduces band gap (3.78 eV) of α-CN to the required band gap for HER and OER activities. The modification of electronic properties is discussed by the analysis of partial density of states, Löwdin charge and charge density plot. To understand HER and OER activities better, we computed Gibbs free energy change after adsorption of H/O in various doped α-CN systems. We observe that the P doping at C site and B doping at N site of α-CN are best suited for HER and OER respectively. The HER (OER) activity increases by 88.33% (29.35%) for P doped at C site (B doped at N site) of α-CN in comparison to pristine α-CN.     

Bifunctional electrocatalysts for water splitting from a bimetallic (V doped-NixFey) Metal–Organic framework MOF@Graphene oxide composite

An ongoing challenge still lies in the exploration of proficient electrocatalysts from earth-abundant non-precious metals instead of noble metal-based catalysts for clean hydrogen energy through large-Scale electrochemical water splitting. However, developing a non-precious transition metals based, stable electrocatalyst for cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER) is important challenge for modern energy conversion technology. In this report Vanadium doped bimetallic nickel-iron nanoarray, fabricated by carbon supported architecture through carbonization process for electrochemical water splitting. Three types of catalysts were prepared in different molar ratio of Ni/Fe. The electrocatalytic performance demonstrated that the catalyst with equal mole ratio (0.06:0.06) of Ni/Fe possess high catalytic activity for both OER and HER in alkaline and acidic medium. Besides, our findings revealed that the doping of vanadium could play a strong synergetic effect with Ni/Fe, which provide a small overpotential of 90 mV and 210 mV at 10 mA cm^?2 for HER and OER respectively compared to the other two catalyst counterparts. Also, the catalyst with 1:1 (Ni/Fe) molar ratio showed a high current density of 208 mA cm^?2 for HER at 0.5 M H₂SO₄ and 579 mA cm^?2 for OER at 1 M KOH solution, the both current densities are much higher than the other two catalysts (different Ni/Fe ratio). In addition, the presented catalysts showed extremely good durability, reflecting in more than 20 h of consistent Chronoamprometry study at fixed overpotential η = 250 mV without any visible voltage elevation. Similarly, the (Ni/Fe) equal ratio catalyst showed better corrosion potential 0.209 V vs Ag/AgCl and lower current density 0.594 × 10^?12 A cm^?2 in high alkaline medium. The V-doping, MOF/GO surface defects are significantly increased the corrosion potential of the V-Ni_xFe_y-MOF/GO electrocatalyst. Besides, the water electrolyzed products were analysed by gas chromatography to get clear insights on the formed H₂ and O₂ products.     

An emerging bidirectional auxetic post-phosphorene ε-SnO monolayer: A promising Janus semiconductor with photocatalytic activity for solar-driven water splitting reaction

The design of two-dimensional (2D) auxetic semiconductors satisfying the rigorous requirements of photocatalytic water-splitting remains challenging. Anisotropic Janus monolayers display excellent potential for water splitting owing to their high photocatalytic activity, while their scarcity proves to be a disadvantage for wide application. Herein, we propose an anisotropic auxetic Janus 2D photocatalyst, a structurally stable ε-SnO monolayer, using first-principles calculations. Monolayer ε-SnO exhibits extraordinary flexibility due to its ultralow Young's moduli and high critical crack strain. Particularly, the large negative in-plane Poisson's ratios are predicted to be ?0.14/-0.17 along the x-/y-direction, which are larger than most previously reported 2D materials. It has a wide indirect bandgap, straddling the redox potentials of water, which varies with the in-plane strain. Radiation-induced carriers can drive the simultaneous occurrence of both hydrogen (HER) and oxygen (OER) evolution half reactions, even when they are under strain. The anisotropic carrier mobility can reach 625.86 cm²·V^?1·s^?1 and the absorption coefficients are predicted to reach up to the order of 10⁵ cm^?1, which is favorable for the photoexcited carrier to migrate to the active sites for water splitting. Interestingly, after transition metal atoms (from Sc to Zn) decoration, Mn/ε-SnO and Cr/ε-SnO as high-efficient single-atom HER photocatalysts are capable of driving HER with ultralow overpotentials of ?0.002 V and ?0.033 V, respectively, outperforming commercial Pt (?0.09 V). Meanwhile, the Cu/ε-SnO with a low-overpotential (0.385 V) is significantly better for neutral OER than IrO₂ (0.55 V) that is widely accepted in industrial applications.     

N,S co-doped NiCo2O4@CoMoO4/NF hierarchical heterostructure as an efficient bifunctional electrocatalyst for overall water splitting

Electrocatalytic overall water splitting technology has received considerable attention in recent years. The fabrication of low-cost, earth-rich and potent bifunctional electrocatalysts is vital for hydrogen evolution (HER) and oxygen evolution reactions (OER). Herein, the N and S co-doped NiCo₂O₄@CoMoO₄ heterostructures (N, S–NCO@CMO₄₀₀) are fabricated by CVD and hydrothermal methods. N and S atoms as auxiliary active centers can increase the activity of Ni, Co and Mo atoms at the same time. Hierarchical heterostructures generate more interfaces to accelerate mass transfer and enlarge the electrochemical surface area, which greatly enhances the catalytic activity. The catalyst displays outstanding OER performance. The overpotentials of OER and HER are 165 and 100 mV at a current density of 10 mA cm^?2, respectively. More importantly, the N, S–NCO@CMO₄₀₀-based water splitting cell has a low voltage of 1.46 V at 10 mA cm^?2. Furthermore, the N, S–NCO@CMO₄₀₀ runs for 120 h in stable operation. This work provides new ideas for the design of hierarchical heterostructures with two-element incorporation.     

Metal-nonmetal atom co-doping engineered transition metal disulfide for highly efficient hydrogen evolution reaction

The development of effective and non-precious electrocatalyts for hydrogen evolution reaction (HER) has attracted massive research interests. Herein, we report a density functional theory (DFT) investigation on the activation and optimization of Molybdenum disulfide (MoS₂) monolayer as efficient HER electrocatalysts by cobalt-nonmetal atom (X = B, C, N, P, Se) codoping. Our results show that three CoX-MoS₂ (X = C, N, and Se) catalysts display enhanced HER performance with |ΔG_H|s in the range of 0.12–0.23 eV. Careful electronic structure analysis manifests that the favorable H adsorption process on the MoS₂ basal plane is induced by suitable in-gap states upon codoping. Furthermore, appropriate biaxial strain can help optimize the HER performance of these co-doped systems, e.g, the ΔG_Hs of CoC@MoS₂, CoN@MoS₂, and CoSe@MoS₂ reaches 0.0 eV, ?0.04 eV, and ?0.01 eV at 1.86% tensile strain, 5% compressive strain, and 4% compressive strain, respectively. Our work offers a highly promising catalyst for HER and guides the atomic design of more efficient non-noble electrocatalysts.     

Ni/Ce co-doping δ-MnO2 nanosheets with oxygen vacancy for enhanced electrocatalytic oxygen evolution reaction

The design and manufacture of strongly engaged, low-cost, and resilient oxygen evolution reaction (OER) electrocatalysts is the most challenging task in electrochemical hydrolysis. Herein, Ce and Ni co-doped MnO₂ (NiCe/MnO₂) nanosheets (NSs) with oxygen vacancy (V_O) and abundant active sites have been prepared in one step employing a defect strategy. The co-doping of Ce/Ni on the one hand reduced the catalyst particle size and increased the specific surface area, which promoted the exposure of more active sites. On the other hand, heteroatom doping altered the species the crystalline surface, stimulating the formation of Vo and thus activating the catalyst performance simultaneously. The OER performance of NiCe/MnO₂ NSs was significantly enhanced over the pure δ-MnO₂, with an overpotential of 170 mV (10 mA cm^?2), which was verified by density functional theory. This work shows a straightforward and practical method for making non-precious metal electrocatalysts with high electrochemical hydrolysis performance.     

Defects and doping engineered two-dimensional o-B2N2 for hydrogen evolution reaction catalyst: Insights from DFT simulation

In this work, a detailed investigation of the structural and electronic properties and hydrogen evolution reaction (HER) activity of the pristine, vacancy and carbon (C) doped o-B₂N₂ monolayer is carried out using first-principles based density functional theory. The creation of vacancy and C doping modulates structural and electronic properties of the monolayers and enhances the HER activity of o-B₂N₂. The BN vacancy defect, C doping at B and N sites in the monolayer enhances the magnitude of HER activity by 77.34%, 86.71% and 83.59% as compared to pristine monolayer. The modulation in the HER activity of the o-B₂N₂ is due to the redistribution of charge after induction of vacancy and dopant. Our results suggest that the C doping makes o-B₂N₂ metallic which can be utilized as an “electrocatalyst” whereas BN vacancy defected o-B₂N₂ monolayer is semiconducting with a band gap of ～1 eV and can be used as “photocatalyst” for HER activity.     

N-doped carbon wrapped CoFe alloy nanoparticles with MoS2 nanosheets as electrocatalyst for hydrogen and oxygen evolution reactions

Developing efficient and cost-effective transition metal-based electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is crucial to generate clean and renewable hydrogen energy. The construction of hybrid catalysts with multiple active sites is an effective approach to promote catalytic performance. Herein, a molybdenum disulfide (MoS₂)-based hybrid with N-doped carbon wrapped CoFe alloy (MoS₂/CoFe@NC) was synthesized through a typical hydrothermal method. The MoS₂/CoFe@NC exhibits excellent electrocatalytic performance with overpotentials of 172 mV for HER and 337 mV for OER at 10 mA cm⁻², and long-term stability of 24-h electrolytic reaction in 1 M KOH solution. The chemical coupling between MoS₂ and CoFe@NC provides improved electronic structures and more accessible active sites. The CoFe@NC substrate accelerates the charge transfer to MoS₂ through a synergistic effect. This work demonstrates that the CoFe@NC is a promising substrate for depositing MoS₂ nanosheets (NSs) to achieve excellent catalytic performance for both HER and OER.     

Predicted superior hydrogen evolution activities of MoC via surface dopant

Molybdenum carbides (MoC) are regarded as promising candidates for electrocatalytic hydrogen evolution reaction (HER) as their stabilities, high conductivities. Non-metallic doping is a robust way to enhance the HER activity of MoC in experiments, yet the systematic theoretical study is still lacking. In this work, we investigate the surface doping effect on HER activity of C-terminated γ-MoC(100) by density functional theory (DFT). The thermodynamical stability and realistic catalytic surface of doped surfaces, including mono- and co-doping by three elements (N, P and S) with various doping ratios, are verified by formation energies and surface Pourbaix diagrams, respectively. According to the hydrogen adsorption ability on different coverage and the calculated exchange current densities (i₀) of the doped surfaces, the surfaces doping in range of (P% > 60% and N% > 5%), (60% < N% <85% and P% < 25%), and (60% < N% < 85% and S% < 25%), show larger i₀ (i₀ > 4 mA/cm²). Especially the N/P co-doping γ-MoC(100), their larger i₀ in greater range enables their promising excellent performance in hydrogen evolution in experiments. The improved HER activities of doped MoC(100) are ascribed to suitable hydrogen adsorption abilities tuned by suitable p_z-band centers and the charge redistribution. Our DFT simulations provide more insight and guidance for improving the HER performance of electrode catalysts using non-metallic doping effects.     

Ni3S2-MoSx nanorods grown on Ni foam as high-efficient electrocatalysts for overall water splitting

In order to solve the problem of large overpotential in water electrolysis for hydrogen production, transition metal sulfides are promising bifunctional electrocatalysts for hydrogen evolution reaction/oxygen evolution reaction that can significantly reduce overpotential. In this work, Ni₃S₂ and amorphous MoS_x nanorods directly grown on Ni foam (Ni₃S₂-MoS_x/NF) were prepared via one-step solvothermal process, which were used as a high-efficient electrocatalyst for overall water splitting. The Ni₃S₂-MoS_x/NF composite exhibits very low overpotentials of 65 and 312 mV to reach 10 mA cm⁻² and 50 mA cm⁻² in 1.0 M KOH for HER and OER, respectively. Besides, it exhibits a low Tafel slope (81 mV dec⁻¹ for HER, 103 mV dec⁻¹ for OER), high exchange current density (1.51 mA cm⁻² for HER, 0.26 mA cm⁻² for OER), and remarkable long-term cycle stability. This work provides new perspective for further the development of highly effective non-noble-metal materials in the energy field.     

MoS2/NiFeS2 heterostructure as a highly efficient electrocatalyst for overall water splitting at high current densities

Searching for efficient, stable and low-cost nonprecious catalysts for oxygen and hydrogen evolution reactions (OER and HER) is highly desired in overall water splitting (OWS). Herein, presented is a nickel foam (NF)-supported MoS₂/NiFeS₂ heterostructure, as an efficient electrocatalyst for OER, HER and OWS. The MoS₂/NiFeS₂/NF catalyst achieves a 500 mA cm⁻² current density at a small overpotential of 303 mV for OER, and 228 mV for HER. Assembled as an electrolyzer for OWS, such a MoS₂/NiFeS₂/NF heterostructure catalyst shows a quite low cell voltage (≈1.79 V) at 500 mA cm⁻², which is among the best values of current non-noble metal electrocatalysts. Even at the extremely large current density of 1000 mA cm⁻², the MoS₂/NiFeS₂/NF catalyst presents low overpotentials of 314 and 253 mV for OER and HER, respectively. Furthermore, MoS₂/NiFeS₂/NF shows a ceaseless durability over 25 h with almost no change in the cell voltage. The superior catalytic activity and stability at large current densities (>500 mA cm⁻²) far exceed the benchmark RuO₂ and Pt/C catalysts. This work sheds a new light on the development of highly active and stable nonprecious electrocatalysts for industrial water electrolysis.     

Se-doped cobalt oxide nanoparticle as highly-efficient electrocatalyst for oxygen evolution reaction

Electrolysis of water has been one of the most promising approaches for renewable energy resources while the efficient oxygen evolution reaction (OER) remains challenging. Herein, a series of different ratio of Se doped Co₃O₄ nanoparticles XSe-Co₃O₄ are prepared by hydrothermal method and applied as OER electrocatalysts. Se^2? is doped into the Co₃O₄ crystal lattice by substituting of O^2? and a large number of oxygen vacancies are generated, which provides more available activity sites for OER. Se doping increases the surface ratio of Co²⁺/Co³⁺ and accelerates the electron transport that favors OER activity promotion. The optimized doping ratio of 6%Se–Co₃O₄ presents low overpotential of 281 mV at 10 mA cm^?2, as well as a low Tafel slope of 70 mV dec^?1 in 1 M KOH solution, which has great advantages compared to the recently reported Co₃O₄-based OER electrocatalysts. This work provides new ideas for the development of efficient Co₃O₄-based OER electrocatalysts.     

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.     

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.     

Enriched oxygen vacancy promoted heteroatoms (B,P, N,and S) doped CeO2: Challenging electrocatalysts for oxygen evolution reaction (OER) in alkaline medium

Increasing worldwide energy consumption has prompted considerable study into energy generation and energy storage systems in recent years. Chemical fuels may be produced efficiently via electrocatalytic water splitting, which uses electric and solar power. The development of efficient anodic electrocatalysts for efficient oxygen evolution reaction (OER) is a greater concern of present energy research. Cerium oxide (CeO₂) are promising electrocatalysts that exhibit outstanding OER but their reduced stability obstructs the practical application. A novel strategy was established to construct an effective catalyst of heteroatom (N, B, P and S) doped CeO₂ matrix were prepared. Moreover, the doping of heteroatoms into the CeO₂ matrix processes the improved electronic conductivity, reactive sites, increases the electrochemical catalytic activity, which enhances the water oxidation reaction. Consequently, well-suited alkaline electrolysers were brought together for water oxidation to ideal OER electrocatalytic activity. The OER activity of the electrocatalysts follows the order of S–CeO₂ (190 mV@10 mA cm⁻²), N– CeO₂ (220 mV @10 mA cm⁻²), P– CeO₂ (230 mV @10 mA cm⁻²), B–CeO₂ (250 mV @10 mA cm⁻²) and CeO₂ (260 mV @10 mA cm⁻²) in 1 M of KOH. From the kinetics analysis, Tafel slope value achieved for catalysts CeO₂, B–CeO_2, P–CeO₂, N–CeO₂ and S–CeO₂ are 142 mV dec⁻¹,121 mV dec⁻¹, 102 mV dec⁻¹, 98 mV dec⁻¹ and 83 mV dec⁻¹ respectively. These results validate that the S–CeO₂ electrode is prominent for OER performance with the requirement of cell voltage of 1.42 V at 10 mA cm⁻² current density. In addition, sulphur doped CeO₂ relatively have excellent stability through chrono-potentiometric analysis lasting for 20 h. Although the heteroatoms doped CeO₂ is acts as anode material, the preparation method is widespread, which will reduce the synthesis cost and streamline the preparation of electrode for OER. This research effort delivers a complete advantage for the development of robust, environmentally friendly and highly dynamic electrocatalysts for OER activity.     

Electronic structure modulation of CoSe2 nanowire arrays by tin doping toward efficient hydrogen evolution

The development of highly active, durable and earth-abundant electrocatalysts toward hydrogen evolution reaction (HER) is of great significance for promoting hydrogen energy. As one of the most potential substitutes for Pt-based materials, pyrite cobalt selenide (CoSe₂) still has shortcomings in terms of HER performance possibly due to its unfavorable hydrogen adsorption characteristics. Metal cation doping has been considered as one of the most available methods to modulate the electronic structure of electrocatalysts. Herein, non-transition metal tin (Sn) doped CoSe₂ nanowire arrays grown on carbon cloth have been constructed and fabricated via a simple gas-phase selenization treatment of hydroxide precursor. The successful doping of Sn element into CoSe₂ nanowires was confirmed by many experimental results. The as-prepared catalyst shows an obviously enhanced HER performance in alkaline media. Compared with pristine CoSe₂, the overpotential of Sn doped catalyst with optimal doping content decreases from 189 mV to 117 mV at 10 mA cm^?2 and the Tafel slope declines from 94 mV dec^?1 to 86 mV dec^?1, as well as shows long-term durability for 100 h. Experimental results and further density functional theory (DFT) calculations show that Sn doping can improve the ability of charge transfer and increase the electrochemical surface area, as well as optimize the hydrogen adsorption energy, all of which are instrumental in HER performance improvement. This work not only provides atomic-level insight into regulating the electronic structure of transition metal selenides by main group metal doping, but also broadens the avenue of developing high-efficiency and stable non-precious metal catalysts.     

Carbon nanorod supported metal alloy nanocubes using polydopamine as location reagent for water splitting

Transition metal catalysts were supposed to be the most likely substitute for commercial noble metal catalysts, and the development of highly active and long-term catalyst for water splitting are the future trend. Herein, Ni rectangular nitrogen doped carbon nanorods@Fe–Co nanocubes (Ni-CNRs@Fe–Co cubes) were fabricated via a facile template-free method. This simple strategy not only realizes the structure tailoring, but also achieves high-quality nitrogen-doping. Specifically, nickel dimethylglyoxime [Ni(dmg)₂] with rectangular rodlike structure was firstly synthesized by solution method, then metal-organic frameworks Fe–Co nanocube with different contents were loaded on rectangular carbon nanorods with polydopamine as the locating and the connecting agent, and finally Ni-CNRs@xFe-Co cubes were obtained by a one-step calcination. A series of electrochemical tests were researched on materials with different metal contents in the 1 M KOH solution. The Ni-CNRs@Fe–Co cubes show excellent electrocatalytic activity in the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). For HER and OER, the Tafel slopes were 83.3 mV dec⁻¹ and 71 mV dec⁻¹, the onset potential were −167 mV and 1.62 V, and reached the current densities of 10 mA cm⁻², the overpotential just needed 196 mV and 433 mV, respectively. This novel synthetic strategy will provide a template-free way for cheap electrocatalysts of non-precious metal for OER and HER.     

Cobalt phosphide nanoparticles embedded in 3D N-doped porous carbon for efficient hydrogen and oxygen evolution reactions

An electrocatalyst based on a unique three-dimensional (3D) N-doped porous carbon sheet networks embedded with CoP₂ nanoparticles (CoP₂@3D-NPC) was synthesized by a facile pyrolysis process as well as an in-situ phosphatization method. The improved CoP₂@3D-NPC hybrid materials show excellent electrocatalytic activity toward HER and OER. This material provides a low overpotential of 126 mV at 10 mA cm⁻² in 0.5 M H₂SO₄ and 167 mV at 20 mA cm⁻² in 1.0 M KOH for HER with a small Tafel slope value of 59 mV dec⁻¹, respectively. Besides, it is also active for the OER under alkaline conditions. Such a prominent property of the CoP₂@3D-NPC electrocatalyst could be attributed to its excellent electrical conductivity of 3D carbon substrate, strong synergistic effect between CoP₂ nanoparticles and carbon nanosheet as well as extra active sites created by the N-doped structure.