Mo Doping Research Articles

Effects of defects on magnetic properties of molybdenum doped indium oxide

Based on density functional theory, this paper systematically calculated the effects of different Mo doping concentrations and neutral intrinsic defects on the electronic structure and magnetic properties of Mo-doped In2O3 (IMO) systems. Studies have shown that the magnetic properties of the IMO system are mainly derived from the hybridization of doped Mo atoms and neighboring O atoms, and as the Mo doping concentration increase, the total magnetic moment of the IMO system also increases, and the magnetic properties increase. In the same configuration, VO, Oi, VIn, and Ini were introduced, and the magnetization energies were 107.29 meV, 2.21 meV, 0.24 meV and-703.72 meV, respectively. Except for the system containing Ini, it transformed into an antiferromagnetic ground state, Others still exhibit ferromagnetic coupling, which shows that different intrinsic defects have a regulatory effect on doping magnetism.

Effect of metal doping in Bi2WO6 micro-flowers for enhanced photoelectrochemical water splitting

Design and fabrication of artificial catalytic systems to mimic natural photosynthesis which can harvest solar energy and directly convert into useable or storable energy resources may resolve the global energy crisis. Remarkably, photocatalysis is an efficient approach to utilize solar photons in order to drive the thermodynamic uphill reaction to generate chemical fuels in presence of efficient photocatalyst. Bismuth tungsten oxide (Bi2WO6) is a typical Aurivillius double perovskite oxides and has received an increasing research interest for water splitting due to moderate bandgap, superior chemical and thermal stability. However, the solar light absorption of bare Bi2WO6 is not significant in visible region, and low charge separation efficiency limits the photocatalytic performance. In the present work, in situ doping of flower like Bi2WO6 microstructure (∼6–8 μm) by metal (Mo, Fe, Zn) may improve the absorption and charge transfer efficiency. The metal doping effectively reduces the bandgap of Bi2WO6 which in turn enhances light absorption in the visible region. Notably, photoelectrochemical water splitting highly improved after metal doping, for example, Mo doping showed highest photocurrent density which is fifty-seven times higher than bare Bi2WO6. The band structure of Bi2WO6 before and after doping has been investigated on the basis of valence band XPS and Mott-Schottky analysis to understand the effect of doping in optoelectronic properties. The enhanced activity may originate due to presence of additional electronic states via doping, lower ionization potential, work function energy and enhanced number of charge carriers at the electrode-electrolyte interface during water splitting.

Effects of Element (Al, Mo, Sn and Fe) Doping on Phase Structure and Mechanical Properties of the Ti-Nb-Based Alloys

In the paper, Ti-18Nb-5X (X = Mo and Sn) and Ti-33Nb-2X (X = Al, Sn, Fe and Mo) alloys were investigated to evaluate the effects of Al, Mo, Sn and Fe doping and different heat treatments on the properties and microstructures of the Ti-Nb-based alloys. The results show that Al decreased the volume of βM in the water-quenched Ti-33Nb-2Al alloy and promoted the formation of β phase in the furnace-cooled Ti-33Nb-2Al alloy. Fe-doping was proven to stabilize the β phase. Sn-doping plays a complicated role to promote the formation of α′′ phase in the water-quenched Ti-33Nb-2Sn alloys but increases the β phase in the furnace-cooled Ti-33Nb-2Sn alloys and Ti-18Nb-5Mo-5Sn. The alloys containing α′′ and βM phases show larger superelastic strains and lower Young’s moduli. In the water-quenched Ti-based alloys, the Young’s modulus decreases, and the superelastic strain is enhanced with the increasing volume of α′′.

Excess dopant effect in platinum‐based alloys toward the oxygen electroreduction reaction

AbstractDoping the PtNi octahedra with trace amount of transition metals has recently been shown to significantly improve the activity and durability of the oxygen reduction reaction (ORR). However, the role of excessive amounts of doped elements on ORR performance is unclear. In this work, PtNi octahedra were synthesized with and without excess Mo dopant. Also, spherical PtNi nanoparticles containing excess Co dopant were synthesized. The ORR performance revealed that PtNiMo octahedra and PtNiCo nanoparticles showed inferior ORR activities compared to bimetallic PtNi octahedra. Based on the electrochemical analysis, we found that unfavorable oxygen‐binding strengths of PtNiMo and PtNiCo catalysts decrease the ORR performances.

Defect engineered 2D mesoporous Mo-Co-O nanosheets with crystalline-amorphous composite structure for efficient oxygen evolution

Two-dimensional (2D) mesoporous metal-oxide (hydroxide) nanomaterials with defects are promising towards the realization of efficient electrocatalysis. Herein, we report a facile and effective one-pot solvothermal route to synthesize mesoporous Mox-Co-O hybrid nanosheets (NSs) which is composed of crystalline Mo4O11 and amorphous cobalt hydroxide. Due to the corrosion of 1-octylamine at high temperatures, abundant mesoporous holes are created in situ over the Mox-Co-O hybrid NSs during the solvothermal process, which is beneficial to increasing the electrochemical surface area. The dimension of the Mox-Co-O NSs, size of mesoporous and the concentration of defects can be easily modulated by controlling the molar ratio of Mo/Co. Electrochemical measurements reveal that the 2D mesoporous Mox-Co-O NSs show an excellent activity for the oxygen evolution reaction with the highest catalytic activity of η10 = 276 mV at 10 mA cm−2 in 1 mol L−1 KOH. Enhanced adsorption of intermediates and abundant oxygen vacancies achieved by appropriate Mo doping are the two main factors that contribute to the excellent catalytic activity of Mo0.2-Co-O NSs. This work, with the construction of 2D metal-oxide (hydroxide) crystalline-amorphous nanomaterials possessing abundant holes, oxygen vacancies and enhanced adsorption of intermediates, provides important insight on the design of more efficient catalysts.

Revealing the Role of Mo Doping in Promoting Oxygen Reduction Reaction Performance of Pt3Co Nanowires

Highly active and durable electrocatalysts towards oxygen reduction reaction (ORR) are imperative for the commercialization application of proton exchange membrane fuel cells. By manipulating ligand effect, structural control, and strain effect, we report here the precise preparation of Mo-doped Pt3Co alloy nanowires (Pt3Co-Mo NWs) as the efficient catalyst towards ORR. The as-prepared Pt3Co-Mo NWs deliver high specific activity (0.596 mA cm-2) and mass activity (MA, 0.84 A mg -1Pt), much higher than those of undoped counterparts. Besides activity, Pt3Co-Mo NWs also demonstrate excellent structural stability and cyclic durability even after 50,000 cycles (76% MA retain), again surpassing control samples without Mo dopants. The superior catalytic performance can be attributed to several structural advantages. First, both ultrafine nanowire morphology and controlled growth ensure the exposure of abundant highly active high-index facets, resulting in increased electrochemical active surface area (ECSA, 141 m2 g−1 Pt). Second, one dimensional (1D) Pt nanostructure, particularly ultrafine Pt nanowires, are less subject to dissolution, aggregation, and even Ostwald ripening than nanoparticles, leading to much-improved durability. Third and most importantly, the Mo doping directly changes the local electronic structure of both element Pt and Co, not only effectively endowing the Pt3Co electrocatalysts with an enhanced activity but also efficiently preventing element Co from leaching leading to improved durability.The geometric phase analysis (GPA) strain maps and the density function theory (DFT)calculations were conducted to further analyze the role of Mo dopants. GPA strain maps reveal that Mo dopants are inclined to be the tensile strain cores, generating local lattice expansion to adjust the excessively compressive strain effect introduced by Co alloying. Benefiting from the optimized d-band center, the oxygen binding energy (Eo) on Pt3Co-Mo slabs is closest to the optimal value compared with those of undoped counterparts. Moreover, the energy required to remove Co atoms from Pt3Co slab with Mo doping is increased by 0.195 eV compared to the slab without Mo doping, indicating the electronic effect of Mo dopants to stabilize Co. This work provides not only a facile methodology but also an in-depth investigation of the relationship between structure and properties to provide general guidance for future design and optimization.

Mo-induced in-situ architecture of NixCoyP/Co2P heterostructure nano-networks on nickel foam as bifunctional electrocatalysts for overall water splitting

Transition metal phosphides (TMPs) exhibit excellent competitiveness for electrochemical splitting water due to their high electrical conductivity and remarkable physicochemical stability. However, pure single-phase TMPs still possess some disadvantages, such as the limited number of active sites and difficulty in greatly accelerating mass/charge transfer. Elemental doping is a practical way to manipulate the intrinsic electronic structures of TMPs and optimize the adsorption and desorption process of intermediates during the water splitting reaction. Rational construction of heterostructure electrocatalysts with high catalytic activity and excellent durability shows great potential for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, we developed a nickel foam (NF)-supported NixCoyP/Co2P heterostructure anchoring on N-doped carbon (NixCoyP/Co2P@NF) via the phosphating of the organic frameworks (ZIF-67) with Mo species added. The as-synthesized NixCoyP/Co2P@NF catalyst shows a unique three-dimensional (3D) nano-network morphology with a large specific surface area and abundant channels for mass exchange. Mo doping alters the valence electronic states of the constituent elements in the initial phase (NixCoyP), thus optimizing the proton transfer from P sites to metal sites, while Co species in the secondary phase (Co2P) is conducive to the water decomposition. Moreover, the heterogeneous interface between initial and secondary phases accelerates electron conduction and further enhances the electrocatalytic efficiency. The NixCoyP/Co2P@NF catalyst shows overpotentials of 170 mV for HER and 352 mV for OER at a current density of 100 mA cm−2 in 1.0 M KOH. The current density can reach 100 mA cm−2 by applying a voltage of 1.75 V for overall water splitting in an alkaline water electrolyzer with NixCoyP/Co2P@NF acting as the anodic and cathodic electrodes. This work has achieved a heterostructure catalyst via the heteroatom-dopant induced phase transition and offered an interfacial engineering strategy for further improving the activity of bifunctional TMP catalysts.

Enhanced peroxymonosulfate activation in the morphotropic phase boundary of molybdenum doped LaCoO3-δ perovskite

Perovskite oxides, with an ABO3 general formula, have attracted much attention as effective peroxymonosulfate (PMS) activators because of their composition adjustability and chemical stability. A doping strategy has been applied to enhance the PMS activation capability with the modulation of the crystal structure of the parent LaCoO3-δ perovskite by substituting Co atoms located at the B-site, with high valence state transition metals. Herein, a series of LaCo1-xMoxO3-δ perovskites were prepared with different Mo content, showing a phase transformation from rhombohedral to cubic-like structures. LaCo0.95Mo0.05O3-δ compound is located at the so-called morphotropic phase boundary (MPB) boosting PMS activation performance as well as enhanced stability. The presence of local inhomogeneities, observed as oxygen vacancies, has been detected in the MPB region enhancing the catalytic effect of pollutant degradation. Mo doping induced Co reduction that contributed to the enhanced PMS activation. Sulfate radical was identified to be the dominating reactive specie for LaCo1-xMoxO3-δ catalyzed PMS activation. This work contributes first, to clarifying the role of Mo doping to boost PMS activation, and second to highlighting the crucial role of the reduced oxidation state as well as the oxygen vacancies in the MPB for PMS activation. Impressive results were obtained when LaCo0.95Mo0.05O3-δ compound was deposited in a Lab-grade photoreactor with LED technology, reaching a complete removal of paracetamol in the first minute. This study provided new insight into the rational design of PMS activator and developed a new strategy for heterogeneous active PMS at a photoreactor with immobilized catalysts.

Mo-doped BiVO4 modified with NH2-MIL-88B(Fe) cocatalyst overlayer for enhanced photoelectrochemical water oxidation

The photoelectrochemical (PEC) performance of BiVO4 is limited by poor charge separation and slow surface water oxidation kinetics. Herein, an simple and effective caffeic acid-assisted solvothermal method was developed to grow Fe-based metal–organic framework (NH2-MIL-88B(Fe)) overlayer onto the Mo-doped BiVO4 for efficient PEC water oxidation. The synergistic role of Fe-MOF cocatalyst and Mo dopant resulted in a 3.5-fold photocurrent density (1.46 mA cm−2) increase in comparison with bare BiVO4 (0.46 mA cm−2) at 1.23 V [vs. reversible hydrogen electrode (RHE)] and showed an obviously negative shift of the onset potential (200 mV). The enhanced PEC performance can be attributed to the improved charge separation and injection efficiency with Mo doping and Fe-MOF coating, the introduction of Fe-MOF also increased the utilization of visible-light and served as an efficient electrocatalyst to accelerate the oxygen evolution reaction (OER) kinetics. This work provides a universal strategy for constructing semiconductor/MOFs photoanodes for enhanced photoelectrochemical water splitting.

Effects of coexistence of Mo and Zn vacancies with different valence states and interstitial H on the magneto-optical properties of ZnO: First-principles calculations

Research progress has been achieved on the influence of transition metal Mo doping and Zn vacancy coexistence on the magnetic and optical properties of ZnO. However, the interstitial H impurity in the Mo-doped ZnO system has been neglected. In this work, first principles were used to calculate the effects of the coexistence of different valence states of Mo and Zn vacancies and interstitial H on the magneto-optical properties of ZnO under the framework of density functional theory. Magnetic results showed that when Mo and Zn vacancies have +6 and 0 valences, respectively, the Zn22Mo6+O24(VZn0) system without interstitial H shows the largest magnetic moment and strongest magnetism. In the doped system, the local electrons of the spin-polarized O-2p orbital behave as acceptors near the valence band maximum, and the itinerant electrons behave as donors near the conduction band minimum. The itinerant electrons of the O-2p orbital adjacent to the Zn vacancy mainly contribute to the magnetic properties of the Zn22Mo6+O24(VZn0) system, and they are most beneficial to the design and preparation of new ZnO-based dilute magnetic semiconductors. Analysis of optical properties found that the Zn22Mo6+HiO24(VZn0) system with interstitial H have the easiest separation of electron–hole pairs, the highest mobility, the longest relaxation time, and the strongest built-in electric field when the Mo and Zn vacancies have +6 and 0 valences, respectively. Therefore, this system has the longest carrier lifetime and best activity. In addition, the absorption spectrum of the Zn22Mo6+HiO24(VZn0) system shows the most remarkable red shift in the visible and near-infrared regions. When pH = 0/7, the Zn22Mo6+HiO24(VZn0) system shows the strongest photocatalytic reduction ability. Given its carrier lifetime and activity, absorption spectrum, and redox ability, the Zn22Mo6+HiO24(VZn0) system is relatively the best for the design and preparation of new ZnO-based photocatalysts.

The valence conversion mechanism for Mo‐doped VO2 films with enhanced thermochromic properties

AbstractReducing the phase transition temperature (Tc) of VO2 films to achieve the application in the field of Smart Home is still a challenge. Thus, in the work, the ultra‐thin VO2 films with different Mo doping amounts were successfully prepared by an economic sol‐gel method and atmosphere annealing, aiming to further investigate the mechanism of the decrease of Tc. The results show that the VO2 films with 3 at % Mo doping possess the Tc of 29.5 °C. Notedly, in the as‐prepared films, the maximum transmittance in the visible region (Tvis) is 46.3 % and the solar direct transmittance (Tsol) is 45.8 %. According to the XPS spectra, it is confirmed that the Mo doping prominently induces the valence change of V ions from +4 to +3, inhibiting the strain in the phase transition process of VO2 films, and leading to the decrease of Tc. Our work will provide a feasible solution for reducing the Tc of the ultra‐thin VO2 films.

Nontrivial Doping Evolution of Electronic Properties in Ising-Superconducting Alloys.

Transition metal dichalcogenides offer unprecedented versatility to engineer 2D materials with tailored properties to explore novel structural and electronic phase transitions. In this work, the atomic-scale evolution of the electronic ground state of a monolayer of Nb1- δ Moδ Se2 across the entire alloy composition range (0 < δ< 1) is investigated using low-temperature (300 mK) scanning tunneling microscopy and spectroscopy (STM/STS). In particular, the atomic and electronic structure of this 2D alloy throughout the metal to semiconductor transition (monolayer NbSe2 to MoSe2 ) is studied. The measurements enable extraction of the effective doping of Mo atoms, the bandgap evolution and the band shifts, which are monotonic with δ. Furthermore, it is demonstrated that collective electronic phases (charge density wave and superconductivity) are remarkably robust against disorder and further shown that the superconducting TC changes non-monotonically with doping. This contrasting behavior in the normal and superconducting state is explained using first-principles calculations. Mo doping is shown to decrease the density of states at the Fermi level and the magnitude of pair-breaking spin fluctuations as a function of Mo content. These results paint a detailed picture of the electronic structure evolution in 2D TMD alloys, which is of utmost relevance for future 2D materials design.

Heterostructured Mo‐Doped CoP on MXene Supports Enhanced the Alkaline Hydrogen Evolution Activity

AbstractThe development of safe, efficient, and non‐noble‐metal electrocatalysts is a promising approach for hydrogen energy production. However, due to low electrical conductivity and weak stability, non‐noble metal catalysts for HER are significantly limited in practice. Here, a method for low‐cost catalysts was reported for synthesizing Mo‐CoP/Ti3C2Tx composites in which Mo‐doped CoP materials were facilely grown on the surface of Ti3C2Tx MXene. The introduction of MXene and the doping of Mo promoted electron transfer and increased the active sites compared with CoP. As HER electrocatalysts, the Mo‐CoP/Ti3C2Tx materials exhibited a good HER activity with a low overpotential of only 117 mV. What's more, these catalysts had shown excellent electron conductivity, fast catalytic dynamics, and a boosted electrochemical active surface. Suitable synthetic ratios were obtained by optimizing the MXene substrate and the Mo doping amount. This work provided a new guide for the design and exploration of MXene based electrocatalysts.

Molybdenum‐doped ordered L10‐PdZn nanosheets for enhanced oxygen reduction electrocatalysis

AbstractUltrathin Pd‐based two‐dimensional (2D) nanosheets (NSs) with tunable physicochemical properties have emerged as promising candidate for oxygen reduction reaction (ORR). Unfortunately, structurally ordered Pd‐based NSs can be hardly prepared as high temperature annealing (&gt;600°C) is necessary for disorder to order phase transition, making it a considerable challenge for morphology control. Herein, a new class of ultrathin structurally ordered Mo‐doped L10‐PdZn NSs with curved geometry and abundant defects/lattice distortions is reported as an efficient oxygen reduction electrocatalyst in alkaline solution. It is found that Mo(CO)6 serves as reducing agent and Mo source to generate the unique ordered 2D morphology, which leads to the significantly modified electronic structure. The developed L10‐Mo‐PdZn NSs exhibit excellent ORR mass activity of 2.6 A mgPd−1 at 0.9 V versus reversible hydrogen electrode, 31.5 and 17.6 times higher than those of Pd/C and Pt/C, respectively, outperforming most of the reported Pd‐based ORR electrocatalsyts. Impressively, L10‐Mo‐PdZn NSs is extremely stable for ORR, with only 2.3% activity loss after 10 000 potential cycles. Density functional theory study suggests that ordered L10 structure and Mo doping can raise the vacancy formation energy of Pd atom and thus promote the ORR stability.

Reprogramming thermodynamic-limiting oxidation cycle in NiFe-based oxygen evolution electrocatalyst through Mo doping induced surface reconstruction

Engineering of robust nonprecious electrocatalysts toward anodic oxygen evolution reaction (OER) is of great significance for lowering the cost and energy consumption for renewable fuel production. Herein, we report NiFeMoOx nanosheets as high-performance OER electrocatalyst through promoting the thermodynamic-limiting oxidation cycle process in NiFe oxyhydroxide via high-valence Mo doping. The NiFeMoOx nanosheets are prepared by an elaborate in-situ solvothermal etching-depositing process with NiFe alloy framework as substrate and metal precursors. The resultant nanosheets exhibit outstanding alkaline OER activity, requires only 235/282/327 mV overpotentials to achieve current density of 10/100/300 mA cm−2, respectively, with a good long-term stability at 20 mA cm−2 for 72 h. Besides, the Tafel slope low to 28.1 mV dec−1 indicates a favorable OER kinetics. The superior catalytic activity of NiFeMoOx nanosheets should be attributed to the lower oxidation states of Ni and Fe induced by high-valence dopant, leading to easier surface reconstruction at low charge oxidation cycling during OER, thereby effectively reducing the overpotential. The synergy between the electronic effect among multimetallic sites and the unique morphology is expected to inspire the development of robust OER electrocatalyst for industrial application.

Toughening (NbTaZrW)C high‐entropy carbide ceramic through Mo doping

AbstractPreviously, we investigated the mechanical properties of a series of multi‐cation high‐entropy ceramic carbides and found that (NbTaZrW)C exhibits the best combination of nanohardness and toughness. In the current study, we explored the possibility of further hardening and/or toughening of this carbide through cation‐site Mo doping. The results show that MoC has at least 20 at.% solubility in (NbTaZrW)C. There is a tight positive relationship between average lattice distortion and mixing enthalpy; and when cation‐site Mo content is below 10 at.%, the “entropy effect” outweighs the “enthalpy effect,” leading to increased phase stability. As Mo content increases, the sacrifice of hardening is much less pronounced in comparison with that of the achievement of toughening. Quantitatively, as Mo in cation sites increases to 20 at.%, the toughness of (NbTaZrW)C is increased by ∼18%, whereas the nanohardness undergoes only ∼7% reduction. More intriguing, the 5 at.% Mo‐doped (NbTaZrW)C exhibits simultaneous improvement of nanohardness and toughness. This hardening/toughening behavior is associated with the complex and hybrid effects from lattice distortion, bonding nature as well as dislocation slip behavior. In general, this study shows the possibility of paving the way for the design and search of novel transition metal carbides with a better combination of hardness and toughness.

Activating lattice oxygen in NiFe-based (oxy)hydroxide for water electrolysis

Transition metal oxides or (oxy)hydroxides have been intensively investigated as promising electrocatalysts for energy and environmental applications. Oxygen in the lattice was reported recently to actively participate in surface reactions. Herein, we report a sacrificial template-directed approach to synthesize Mo-doped NiFe (oxy)hydroxide with modulated oxygen activity as an enhanced electrocatalyst towards oxygen evolution reaction (OER). The obtained MoNiFe (oxy)hydroxide displays a high mass activity of 1910 A/gmetal at the overpotential of 300 mV. The combination of density functional theory calculations and advanced spectroscopy techniques suggests that the Mo dopant upshifts the O 2p band and weakens the metal-oxygen bond of NiFe (oxy)hydroxide, facilitating oxygen vacancy formation and shifting the reaction pathway for OER. Our results provide critical insights into the role of lattice oxygen in determining the activity of (oxy)hydroxides and demonstrate tuning oxygen activity as a promising approach for constructing highly active electrocatalysts.

Synergistic effect of La+Mo addition and optimum pH on the photocatalytic dye decomposition efficiency of spray pyrolyzed ZnO thin films

This work explores the photocatalytic degradation efficiency of lanthanum (La) and molybdenum (Mo) incorporated ZnO films deposited by nebulizer spray pyrolysis onto glass slides. The influence of La and (La + Mo) doping on certain physical properties was investigated. Photocatalytic behavior of the films was studied against methyl orange (MO) and methylene blue (MB) dyes. The impacts of dye adsorption, point of zero charge, and dye solution pH on the catalytic activity of ZnO:La:Mo films were probed and compared with those of their counterparts ZnO and ZnO:La thin films. The obtained results demonstrated that ZnO:La:Mo photocatalyst exhibited greater efficiency, reaching 98% and 85% degradation after 60 min for the cationic and anionic dyes, respectively for optimum pH. The degradation reactions follow the first-order kinetics and the rate of degradation increases by adding La and (La + Mo) to ZnO. The ZnO:La:Mo thin film exhibits excellent recyclability and stability even after five runs. A possible photocatalytic mechanism has also been proposed.

High strength and ductility of an additively manufactured CrCoNi medium-entropy alloy achieved by minor Mo doping

The effect of minor Mo doping on the microstructure and mechanical properties of a (CoCrNi)95Mo5 medium-entropy alloy (MEA) was studied by selective laser melting (SLM) to architect the dislocation-formed sub-grains, ultrafine (Mo, Cr)-enriched μ precipitates and various lattice defects. High strength and ductility were achieved in the as-SLMed (CoCrNi)95Mo5 alloy, where the yield strength, ultimate tensile strength (UTS) and fracture strain were 0.79 GPa, 0.97 GPa and 35.9%, respectively. The superior mechanical properties were associated with the typical hierarchical microstructure that were featured by the high-density dislocations-formed equiaxed sub-grains, the columnar sub-grains separated by low-angle grain boundaries (LAGBs), the fine (Mo, Cr)-enriched μ precipitates and the lattice defects including dislocations, stacking faults (SFs) and Lomer-Cottrell locks (LCs) in the matrix. The results have demonstrated the potential of applying precipitation strengthening in CoCrNi-based MEAs through additive manufacturing to achieve superior mechanical properties.

Molybdenum-induced tuning 3d-orbital electron filling degree of CoSe2 for alkaline hydrogen and oxygen evolution reactions

The development of high-performance non-precious metal-based robust bifunctional electrocatalyst for both hydrogen evolution reaction (HER) and oxygen evolution reactions (OER) in alkaline media is essential for the electrochemical overall water splitting technologies. Herein, we demonstrate that the HER/OER performance of CoSe2 can be significantly enhanced by tuning the 3d-orbital electron filling degree through Mo doping. Both density functional theory (DFT) calculations and experimental results imply that the doping of Mo with higher proportion of the unoccupied d-orbital (Pun) could not only serve as the active center for water adsorption to enhance the water molecule activation, but also modulate the electronic structures of Co metal center leading to the optimized adsorption strength of *H. As expected, the obtained Mo-CoSe2 exhibits a remarkable bifunctional performance with overpotential of only 85 mV for HER and 245 mV for OER to achieve the current density of 10 mA/cm2 in alkaline media. This work will provide a valuable insight to design highly efficient bifunctional electrocatalyst towards HER and OER.