The exploration of efficient, robust and nonprecious transition metal electrocatalysts for electrochemical hydrolysis is urgently needed. Herein, we developed Ni(OH)(2) with 3D nanoflower structure on the titanium mesh by a simple electrodeposition method. The Ni(OH)(2)/Ti exhibited excellent oxygen evolution reaction performance and achieved 10 mA cm(-2) at 190 mV with fast kinetics in alkaline conditions. Ni2P, NiS2 and NiSe2 were prepared by solid-phase reaction, and the 3D nanoflower increased the open structure and greatly enhanced catalytic activity. The Ni2P/Ti electrode required an overpotential of 52, 88 and 109 mV to reach 10 mA cm(-2) for hydrogen evolution reaction in acidic, alkaline and neutral media, respectively. The results of electrochemical measurements and mechanistic studies showed that the catalytic activity of HER: Ni2P > NiS2 > NiSe2 > Ni(OH)(2). The Ni2P/Ti and Ni(OH)(2)/Ti electrodes were assembled into an integrated water splitting electrolytic cell. The water electrolysis device assembled with the Ni2P/Ti and Ni(OH)(2)/Ti electrodes only needed a low potential of 1.608 V to achieve 50 mA cm(-2) in alkaline environment and was operated stably for 50 h.

Designing flexible single-atom catalysts with tunable single-atom centers and coordination environments is crucial for highly active and selective electrochemical catalysis. Using density functional theory calculations, a range of 32 two-dimensional...

AbstractThe advancement of Zn–Se batteries has been hindered by significant challenges, such as the sluggish kinetics of Se cathodes, limited Se loading, and uncontrollable formation of Zn dendrites. In this study, a bidirectional optimization strategy is devised for both cathode and anode to bolster the performance of Zn–Se batteries. A novel bowl‐in‐ball structured carbon (BIBCs) material is synthesized to serve as a nanoreactor, in which tin‐based materials are grown and derived in situ to construct cathodes and anodes. Within the cathode, the multifunctional host material (SnSe@BIBCs) exhibits large adsorption capacity for selenium, and demonstrates supreme catalytic properties and spatially confined characteristics toward the selenium reduction reaction (SeRR). On the anode, Sn@BIBCs displays triple‐induced properties, including the zincophilic of the internal metallic Sn, the homogenized spatial electric field from the 3D spatial structure, and the curvature effect of the bowl‐shaped carbon. Collectively, these factors induce preferential nucleation of Zn, ensuring its uniform deposition. As a result, the integrated Zn–Se battery system achieves a remarkable specific capacity of up to 603 mAh g−1 and an impressive energy density of 581 W kg−1, highlighting its tremendous potential for practical applications.

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Electrochemical coupling nitrate-to-ammonia (NO3–-to-NH3) with urea oxidation reaction (UOR) is attractive for both energy-saving ammonia synthesis and comprehensive nitrogen-rich wastewater treatment. However, developing the efficient electrocatalyst that simultaneously promotes hydrogenation of NO3– and UOR is still challenging. Here, we engineered the porous CoMoO4 nanosheets with rich low-valent Mo sites (Mo(L)-CoMoO4-x) as a difunctional electrocatalyst for both NO3–-to-NH3 and UOR. The Mo(L)-CoMoO4-x displayed high Faradaic efficiency (93.33%) and selectivity (91.16%) for NO3–-to-NH3 and low potential (1.31V vs. RHE) at 100mAcm-2 toward UOR. Impressively, a low cell voltage of 1.83V was needed for coupling UOR with NO3–-to-NH3 in two-electrode system. Mechanism study revealed that the introduction of low-valent Mo sites in CoMoO4 nanosheets accelerated the activation kinetics and multistep hydrogenation of NO3–, and also promoted the reconstruction of active CoOOH species for UOR, resulting the difunctional catalytic property for NO3–-to-NH3 and UOR.

Unveiling the composition-dependent catalytic mechanism of Pt-based alloy cathodes for the oxygen reduction reaction (ORR) helps improve the proton exchange membrane fuel cells. Using density functional theory calculations, this study investigates the ORR catalytic performance of the Pt-Ni system with various compositions (1.00, similar to 0.99, 0.75, 0.50, 0.25, similar to 0.01, and 0.00). The ordered solid solution PtNi3(111) system shows activity comparable to Pt(111) and is cost-effective. The Ni1/Pt(111) system, featuring a single Ni atom on the Pt(111) surface as a surface single-atom alloy (SSAA), demonstrates the highest activity with an overpotential of only 0.28, which could be further reduced to 0.21 V by decreasing the surface Ni concentration to 1/16 monolayer coverage. The predicted high activity of Ni1/Pt(111) is confirmed when considering factors such as the implicit solution environment, constant potential conditions, and protonation capability. Moreover, surface-adsorbed oxygen species driven by reaction conditions stabilize these single Ni atoms of Ni1/Pt(111) by preventing segregation and dissolution processes, thereby exhibiting a dual functionality. This study reveals the composition dependence of Pt-based alloys and highlights the stability mechanisms of SSAA catalysts during the ORR.

Saturn-like (SL) N-doped VS2 as a cathode material for aqueous zinc-ion batteries (ZIBs) is synthesized into hollow mesoporous carbon spheres via a confinement growth strategy. SL VS2@CS shows a novel three-step deintercalation process at a wide voltage range (0-1 V), which efficiently enhances the Zn2+ storage capacity. In addition, the confined effect of SL VS2@CS can emphatically inhibit the pulverization and volume effect induced by massive Zn2+ insertion, and the finite element simulation confirms that the Saturn-like structure can alleviate the stress distribution caused by the zincification process. The density functional theory calculation verifies that the N-doped VS2@CS greatly reduces the migration energy barrier. The electrochemical reaction process and structure evolution of SL VS2@CS in ZIBs are analyzed by ex situ methods, which demonstrate the three-step deintercalation mechanism and highly reversible process. The soft-package ZIBs assembled with SL VS2@CS as the cathode exhibit the potential for practical application with superior cycling stability (322.2 mA h g(-1) at 0.5 C, 500 cycles) and good rate performance.

Zinc-selenium batteries have high specific and volumetric capacities, but practical development faces key challenge in achieving stable zinc metal anodes, and avoiding zinc dendrite growth, hydrogen evolution reaction (HER) and corrosion. Here, a zinc foam substrate is employed to fabricate three-dimensional gradient electrodes Zn foam@Cu@CuSe2 (ZFCCS) with gradient change of zincophilicity and conductivity. Experimental observations and simulations collectively confirm that the three-dimensional structure and gradient design effectively homogenize interfacial ion flux and diminish local current density. This optimization of the zinc deposition path synergistically fosters high flux and deep deposition of zinc metal while simultaneously preventing dendrite growth. The results demonstrate that the developed ZFCCS electrode produces an excellent Coulombic efficiency of 99.5 % over 1000 plating/stripping cycles, and the corresponding symmetric cell provides an ultra-long dendrite-free cycle life of 800 h at 5 mA cm- 2 and 2 mAh cm- 2 with a low overpotential of 27.4 mV. In addition, the Zn-Se full cell based on the designed ZFCCS composite anode exerts superior stable cycle life (358.1 mAh g- 1 at 2 A g- 1 after 1000 cycles). Therefore, the gradient design strategy based on 3D electrodes will be a reference for high performance energy storage devices.

The practical application of room-temperature sodium-sulfur (RT Na-S) batteries is blocked by the notorious shuttle effect of sodium polysulfides (NaPSs) and sluggish refox reaction kinetics. Single-atom catalysts (SACs) have been widely studied for boosting the energy storage performance of RT Na-S batteries. Nevertheless, the catalytic centers of SACs reported so far have focused mainly on symmetrical metal-N-4 structures, which offer weak bonding affinity toward polar NaPSs, leading to detrimental shuttle effect and sluggish sulfur conversion kinetics. Herein, a novel asymmetrical Mn-N-2 structure is implanted into nitrogen-doped carbon nanofibers (Mn-N-2/CNs) through thermal NH3 etching of a symmetrical Mn-N2O2 structure. The Mn-N-2 structure promotes the bonding affinity and catalytic conversion of NaPSs due to the strengthened d-p orbital-hybridization between the d orbital of Mn in the Mn-N-2 structure and the p orbital of S in NaPSs. Consequently, Mn-N-2/CNs@S achieves a high capacity of 458 mAh g(-1) at 3.0 C with a capacity decay of 0.23% over 2300 cycles. This work offers a promising pathway for regulating the coordination number of SACs with strengthened d-p orbital-hybridization for high-performance RT Na-S batteries.

Understanding the structural evolution of single-atom catalysts (SACs) in catalytic reactions is crucial for unraveling their catalytic mechanisms. In this study, we utilize density functional theory calculations to delve into the active phase evolution and the oxygen reduction reaction (ORR) mechanism of tungsten semicarbide-based transition metal SACs (TM1/W2C). The stable crystal phases and optimal surface exposures of W2C are identified by using ab initio atomistic thermodynamics simulations. Focusing on the W-terminated (001) surface, we screen 13 stable TM1/W2C variants, ultimately selecting Pt1/W2C(001) as our primary model. The surface Pourbaix diagram, mapped for this model under ORR conditions, reveals dynamic Pt1 migration on the surface, triggered by surface oxidation. This discovery suggests a novel single-atom evolution pathway. Remarkably, this single-atom migration behavior is also discerned in seven other group VIII SACs, enhancing both their catalytic activity and their stability. Our findings offer insights into the evolution of active phases in SACs, considering substrate structural arrangement, single-atom incorporation, and self-optimization of catalysts under various conditions.

Finding a suitable anode material is a key part of the development of Mg-ion batteries (MIBs) to commercialize. In this work, an outstanding Silicene/BN heterostructure was discovered as a candidate anode material for MIBs by using first-principles calculations. The mixed sp2/sp3 orbital hybridization of silicon atoms makes Silicene monolayer easy to adsorb Mg atoms. The introduction of BN monolayer can effectively buffer the structural deformation and improve the electrochemical performances. Compared to pristine Silicene, the Silicene/BN heterostructure exhibited higher structural stability and Mg adsorption capacity. The diffusion of Mg ions in the heterostructure interlayer was easier with a low barrier of 0.160eV than that on the Silicene monolayer. A comparable low open circuit voltage (0.112V) was also observed. These results indicated the potential of Silicene/BN heterostructure as a high-performance anode material for MIBs.

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 |DGH|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 DGHs 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.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

The low-rate capability and fast capacity decaying of the molybdenum dioxide anode material have been a bottleneck for lithium-ion batteries (LIBs) due to low carrier transport, drastic volume expansion and inferior reversibility. Furthermore, the lithium-storage mechanism is still controversial at present. Herein, we fabricate a new kind of MoO2 nanoparticles with nitrogen-doped multiwalled carbon nanotubes (MoO2/N-MCNTs) as anode for LIBs. The strong chemical bonding (MoOC) endows MoO2/N-MCNTs a strong metal oxide-support interaction (SMSI), rendering electron/ion transfer and facilitate significant Li+ intercalation pseudocapacitance, which is evidenced by both theoretical computation and detailed experiments. Thus, the MoO2/N-MCNTs exhibits high-rate performance (523.7 mAh/g at 3000 mA g-1) and long durability (507.8 mAh/g at 1000 mA g-1 after 500 cycles). Furthermore, pouch-type full cell composed of MoO2/N-MCNTs anodes and commercial LiNi0.6Co0.2Mn0.2O2 (NCM622) cathodes demonstrate impressive rate performance and cyclic life, which displays an unparalleled energy density of 553.0 Wh kg-1. Ex-situ X-ray absorption spectroscopy (XAS) indicates the enhanced lithium-storage mechanism is originated from a partially irreversible phase transition from Li0.98MoO2 to Li2MoO4 via delithiation. This work not only provides fresh insights into the enhanced lithium-storage mechanism but also proposes new design principles toward efficient LIBs.

Developing highly efficient and stable electrocatalysts is the key to realize hydrogen production from industrial electrolytic water. In this study, we constructed Co(OH)(2) and CoP ultrathin nanosheet arrays on titanium mesh using electrodeposition and phosphating processes. In alkaline conditions, the Co(OH)(2)/Ti-2.0 needed overpotentials of 414 and 457 mV to achieve 500 and 1000 mA cm(-2) for oxygen evolution reaction. Mechanism research showed that CoOOH formed by pre-oxidation of Co(OH)(2) was the actual active substance. After low-temperature phosphorization of Co(OH)(2), CoP nanosheets generated abundant defects and increased reactive sites, and CoP/Ti-2.0 exhibited high activity in the all-pH hydrogen evolution reaction (overpotentials of 106, 116, and 131 mV in acidic, alkaline, and neutral solutions at 10 mA cm(-2), respectively). Density functional theory calculations showed the free energy of hydrogen adsorption of CoP. As efficient electrode materials, the Co(OH)(2) and CoP ultrathin nanosheet arrays on Ti mesh can be assembled to an alkaline electrolyzer, which required only 1.530 V to drive 50 mA cm(-2) for overall water splitting with strong durability.

The electrochemical reduction reaction of dinitrogen into ammonia (eNRR) has been considered as one of the most promising candidates to replace the traditional Haber-Bosch process. By using the density functional theory calculations, 20 kinds of atomically dispersed tri-atoms supported on graphdiyne monolayer catalysts MxM ' yM '' 3-x-y/GDY (M, M ', M ''= Cr, Mo, W, Fe) were investigated for the eNRR process. It is found that Cr3/GDY, W3/GDY, and Cr2Mo1/GDY exhibit high stability, selectivity, and activity, with limiting potentials of only-0.36,-0.35, and-0.29 V, respectively. Specifically, by further investigating the most active and exemplar Cr2Mo1/GDY system, in the presence of N2 adsorption on the catalyst, it would promote the desorption of the final product NH3. More importantly, by evaluating the growth energy of the supported atomic metal centers, these catalysts have a very broad theoretical energy window, indicating their possibility of synthesizing. These atomically dispersed metal centers cooperating with the GDY monolayer could promote the multi-step protonation process. Our findings shed light on the rational and precise design of novel catalysts for electrochemical energy con-version and storage.

Regulating the spin states of catalysts to enhance activity is fascinating but challenging. Herein, by using first-principles calculations, single transition-metal (TM) atoms Mo, Re, and Os embedded in nitrogen vacancy of the MoSi2N4 monolayer (TM1/VN-MoSi2N4) were screened out as potential catalysts for electrochemical nitrogen reduction reaction to ammonia. Our findings suggest that the spin states of these active centers can be precisely and gradually tuned through a simple doping strategy. Additionally, doping one O atom into the Mo1/VN-MoSi2N4 system as an example significantly improves catalytic activity. The spin state of Mo1 transitions from high to intermediate while simultaneously breaking the C3v symmetry of the supported atom. These factors synergistically lead to better orbital overlap between the catalyst and intermediates, facilitating subsequent protonation processes and overall catalytic activity. This work provides novel insight into designing, precisely controlling, and revisiting the spin-related catalytic performance in heterogeneous catalysis.

Water dissociation is of fundamental importance in scientific fields and has drawn considerable interest in diverse technological applications. However, the high activation barrier of breaking the O-H bond within the water molecule has been identified as the bottleneck, even for the water adsorbed on the graphene oxide (GO). Herein, using the density functional theory calculations, we demonstrate that the water molecule can be spontaneously dissociated on GO supported by the (111) surface of the copper substrate (Copper-GO). This process involves a proton transferring from water to the interfacial oxygen group, and a hydroxide covalently bonding to GO. Compared to that on GO, the water dissociation barrier on Copper-GO is significantly decreased to be less than or comparable to thermal fluctuations. This is ascribed to the orbital-hybridizing interaction between copper substrate and GO, which enhances the reaction activity of interfacial oxygen groups along the basal plane of GO for water dissociation. Our work provides a novel strategy to access water dissociation via the substrate-enhanced reaction activity of interfacial oxygen groups on GO and indicates that the substrate can serve as an essential key to tuning the catalytic performance of various two-dimensional material devices.

Molybdenum disulfide (MoS2) has been considered a promising high-efficiency, low-cost hydrogen evolution reaction (HER) catalyst in acidic and alkaline media. However, the lack of active sites in the basal plane become the most significant obstacle hindering the widespread application of MoS2. Here, we systematically studied the HER performance of MoS2 plane or edge by co-doping Co atom and other 3d transition metals (TM = Ti-Fe, Ni) by density functional theory calculation methods. Interestingly, the dual atoms doping in both the basal plane and edges of MoS2 is a feasible fabrication with small or negative formation energies. Compared with the pristine MoS2 electrocatalyst, the HER performance in these doped systems is largely enhanced in both basal plane and edges due to the effective charge regulation on the S site by dual atom doping. Remarkably, close to zero H adsorption free energy (DGH = -0.161-0.119 eV) is identified for the TM-Co co-doped MoS2 basal, indicating that they are potential alternate HER electrocatalysts of Pt. Our study provides a new strategy to design highly efficient non-noble metal electrocatalysts accessibility for energy-related applications. ?? 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Nanobox structural Fe7S8/MoS2 carbon nanofibers (NB Fe7S8/MoS2-CNFs) are synthesized by the process of electrospinning-sulfuration-hydrothermal, which construct a multidimensional structure with 0D nanoparticles, 1D nanofibers, 2D nanosheets and 3D cross-link networks. NB Fe7S8/MoS2-CNFs display the special dual confined effects, which are the space and interface confinement, respectively. Benefiting from the advantage of multidimensional structure, NB Fe7S8/MoS2-CNFs exhibit remarkable potassium storage capability and stable long cycle (-204.5 mA h g-1 at 1 A g-1 after 500 cycles). The structure evolution of NB Fe7S8/MoS2-CNFs in potassium ion batteries (PIBs) are explored by ex-situ methods, which confirm that dual confined effect can alleviate the volume expansion effectively. Integrating the merits of multidimensional structure and dual confined effects, NB Fe7S8/MoS2-CNFs anode also manifests an outstanding reversibility and long cyclic stability of lithium-ion batteries (LIBs) (-772 mA h g-1 at 1 A g-1 after 500 cycles) and sodium-ion batteries (SIBs) (-368.3 mA h g-1 at 1 A g-1 after 500 cycles). Additionally, the kinetic properties have been studied, which explain the different ion migration laws of alkali metal ion batteries. The density function theory (DFT) calculation further verifies that heterogeneous interfaces can greatly reduce the migration energy barrier. Therefore, this work provides a strategy of dual confined effect to understand the mechanism and kinetics of alkali metal ion batteries.

Sodium-Se (Na-Se) and potassium-Se (K-Se) batteries are prospective candidates for energy storage systems with high theoretical specific capacity and low cost. However, some intractable problems need to be overcome, such as the shuttle effect of polyselenide and the low Se loading, which lead to poor cyclic performance and low capacity. Herein, dual-wall hollow carbon spheres (DWHCSs) modified with cetyltrimethylammonium bromide (CTAB) were designed to be served as a host material (C-DWHCSs) for the load of Se to construct the Se electrode material (C-DWHCSs/Se). Dual-wall hollow structure with satisfactory specific surface area greatly increased the load capacity of Se, which effectively improved the battery capacity. In terms of physical confinement, the gap between two carbon walls provided a buffer space for the volume expansion of Se and prevented the escape behavior of electrode material after expansion pulverization. Based on the chemisorption strategy, the polyselenides were immobilized by CTAB functionalized graphite carbon through the Lewis acid-base interaction, which was demonstrated by theoretical calculation. As a consequence, C-DWHCSs/Se in Na-Se batteries delivered an outstanding cycling performance (-331 mAh g-1 at 2 C after 1000 cycles). For K-Se batteries, they also exhibited a splendid cycling stability (-292 mAh g inverted exclamation 1 at 0.5 C after 500 cycles). (c) 2021 Elsevier Ltd. All rights reserved.