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1.
Electrochemical water splitting for hydrogen generation is a vital part for the prospect of future energy systems, however, the practical utilization relies on the development of highly active and earth‐abundant catalysts to boost the energy conversion efficiency as well as reduce the cost. Molybdenum diselenide (MoSe2) is a promising nonprecious metal‐based electrocatalyst for hydrogen evolution reaction (HER) in acidic media, but it exhibits inferior alkaline HER kinetics in great part due to the sluggish water adsorption/dissociation process. Herein, the alkaline HER kinetics of MoSe2 is substantially accelerated by heteroatom doping with transition metal ions. Specifically, the Ni‐doped MoSe2 nanosheets exhibit the most impressive catalytic activity in terms of lower overpotential and larger exchange current density. The density functional theory (DFT) calculation results reveal that Ni/Co doping plays a key role in facilitating water adsorption as well as optimizing hydrogen adsorption. The present work paves a new way to the development of low‐cost and efficient electrocatalysts towards alkaline HER.  相似文献   

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《中国化学快报》2023,34(4):107622
Controlling the particle size of catalyst to understand the active sites is the key to design efficient electrocatalysts toward hydrogen electrode reactions including hydrogen oxidation and evolution (HOR/HER). Herein, the hydrogen and hydroxyl adsorption on Ru/C could be effectively tuned for HOR/HER by simple controlling the particle sizes. It is found that the metallic Ru (Ru0) is the active site for HOR/HER, while oxidized Ru (Rux+) will hinder the adsorption and desorption of hydrogen on the catalyst. For the HOR, catalyst with small particles is more efficient, due to it is a three-phase interface reaction of gas on the surface of the catalyst. For the HER, the metallic state of Ru is crucial. The deconvolution of hydrogen peaks indicates that the catalytic sites with low hydrogen binding energy (HBE) shoulder the majority of the HOR activity. CO stripping curve further demonstrates that the stronger hydroxyl species (OHad) affinity is beneficial to promote the HOR performance. The results indicate that the design of efficient HOR/HER catalyst should focus on the balance between particle size and metallic states.  相似文献   

5.
In the present work, experimental and theoretical structural studies of two new nitazoxanide (NTZ) complexes, [Co(NTZ)(NO3)2(OH2)] ( 1 ) and [Ni(NTZ)(CH3COO)(OH2)]·CH3COO ( 2 ) were reported. The susceptibility of Staphylococcus aureus and Escherichia coli towards NTZ and its complexes was assessed. NTZ behaves as a monodentate ligand via the thiazole N atom forming distorted octahedral and tetrahedral complexes with Co(II) and Ni(II) ions, respectively. The d‐d transitions were assigned by the aid of time‐dependent density functional theory calculations. The magnetic susceptibility value of 1 remains unchanged in the temperature range of 298–77K, while that of 2 decreases linearly with the temperature to attain 2.79 μB at 77K. Coordination of NTZ (0.084 μmol ml?1) to Co(II) ( 1 ) (0.028 μmol ml?1) and Ni(II) ions ( 2 ) (0.079 μmol ml?1) leads to an improvement in the toxicity against S. aureus.  相似文献   

6.
Ferric oxides and (oxy)hydroxides, although plentiful and low‐cost, are rarely considered for oxygen evolution reaction (OER) owing to the too high spin state (eg filling ca. 2.0) suppressing the bonding strength with reaction intermediates. Now, a facile adsorption–oxidation strategy is used to anchor FeIII atomically on an ultrathin TiO2 nanobelt to synergistically lower the spin state (eg filling ca. 1.08) to enhance the adsorption with oxygen‐containing intermediates and improve the electro‐conductibility for lower ohmic loss. The electronic structure of the catalyst is predicted by DFT calculation and perfectly confirmed by experimental results. The catalyst exhibits superior performance for OER with overpotential 270 mV @10 mA cm?2 and 376 mV @100 mA cm?2 in alkaline solution, which is much better than IrO2/C and RuO2/C and is the best iron‐based OER catalyst free of active metals such as Ni, Co, or precious metals.  相似文献   

7.
Even though transition‐metal phosphides (TMPs) have been developed as promising alternatives to Pt catalyst for the hydrogen evolution reaction (HER), further improvement of their performance requires fine regulation of the TMP sites related to their specific electronic structure. Herein, for the first time, boron (B)‐modulated electrocatalytic characteristics in CoP anchored on the carbon nanotubes (B‐CoP/CNT) with impressive HER activities over a wide pH range are reported. The HER performance surpasses commercial Pt/C in both neutral and alkaline media at large current density (>100 mA cm?2). A combined experimental and theoretical study identified that the B dopant could reform the local electronic configuration and atomic arrangement of bonded Co and adjacent P atoms, enhance the electrons’ delocalization capacity of Co atoms for high electrical conductivity, and optimize the free energy of H adsorption and H2 desorption on the active sites for better HER kinetics.  相似文献   

8.
To explore the structure–function relationships of cobalt complexes in the catalytic hydrogen evolution reaction (HER), we studied the substitution of a tertiary amine with a softer pyridine group and the inclusion of a conjugated bpy unit in a Co complex with a new pentadentate ligand, 6‐[6‐(1,1‐di‐pyridin‐2‐yl‐ethyl)‐pyridin‐2‐ylmethyl]‐[2,2′]bipyridinyl (Py3Me‐Bpy). These modifications resulted in significantly improved stability and activity in both electro‐ and photocatalytic HER in neutral water. [Co(Py3Me‐Bpy)(OH2)](PF6)2 catalyzes the electrolytic HER at ?1.3 V (vs. SHE) for 20 hours with a turnover number (TON) of 266 300, and photolytic HER for two days with a TON of 15 000 in pH 7 aqueous solutions. The softer ligand scaffold possibly provides increased stability towards the intermediate CoI species. DFT calculations demonstrate that HER occurs through a general electron transfer/proton transfer/electron transfer/proton transfer pathway, with H2 released from the protonation of CoII?H species.  相似文献   

9.
Oxide-derived Cu (OD−Cu) featured with surface located sub-20 nm nanoparticles (NPs) created via surface structure reconstruction was developed for electrochemical CO2 reduction (ECO2RR). With surface adsorbed hydroxyls (OHad) identified during ECO2RR, it is realized that OHad, sterically confined and adsorbed at OD−Cu by surface located sub-20 nm NPs, should be determinative to the multi-carbon (C2) product selectivity. In situ spectral investigations and theoretical calculations reveal that OHad favors the adsorption of low-frequency *CO with weak C≡O bonds and strengthens the *CO binding at OD−Cu surface, promoting *CO dimerization and then selective C2 production. However, excessive OHad would inhibit selective C2 production by occupying active sites and facilitating competitive H2 evolution. In a flow cell, stable C2 production with high selectivity of ∼60 % at −200 mA cm−2 could be achieved over OD−Cu, with adsorption of OHad well steered in the fast flowing electrolyte.  相似文献   

10.
Heterostructured nanomaterials, generally have physicochemical properties that differ from those of the individual components, and thus have potential in a wide range of applications. New platinum (Pt)/nickel bicarbonate (Ni(HCO3)2) heterostructures are designed for an efficient alkaline hydrogen evolution reaction (HER). Notably, the specific and mass activity of Pt in Pt/Ni(HCO3)2 are substantially improved compared to the bare Pt nanoparticles (NPs). The Ni(HCO3)2 provides abundant water adsorption/dissociation sites and modulate the electronic structure of Pt, which determine the elementary reaction kinetics of alkaline HER. The Ni(HCO3)2 nanoplates offer a platform for the uniform dispersion of Pt NPs, ensuring the maximum exposure of active sites. The results demonstrate that, Ni(HCO3)2 is an effective catalyst promoter for alkaline HER.  相似文献   

11.
The hexadentate ligand all‐cis‐N1,N2‐bis(2,4,6‐trihydroxy‐3,5‐diaminocyclohexyl)ethane‐1,2‐diamine (Le) was synthesized in five steps with an overall yield of 39 % by using [Ni(taci)2]SO4?4 H2O as starting material (taci=1,3,5‐triamino‐1,3,5‐trideoxy‐cis‐inositol). Crystal structures of [Na0.5(H6Le)](BiCl6)2Cl0.5?4 H2O ( 1 ), [Ni(Le)]‐ Cl2?5 H2O ( 2 ), [Cu(Le)](ClO4)2?H2O ( 3 ), [Zn(Le)]CO3?7 H2O ( 4 ), [Co(Le)](ClO4)3 ( 5 c ), and [Ga(H?2Le)]‐ NO3?2 H2O ( 6 ) are reported. The Na complex 1 exhibited a chain structure with the Na+ cations bonded to three hydroxy groups of one taci subunit of the fully protonated H6(Le)6+ ligand. In 2 , 3 , 4 , and 5 c , a mononuclear hexaamine coordination was found. In the Ga complex 6 , a mononuclear hexadentate coordination was also observed, but the metal binding occurred through four amino groups and two alkoxo groups of the doubly deprotonated H?2(Le)2?. The steric strain within the molecular framework of various M(Le) isomers was analyzed by means of molecular mechanics calculations. The formation of complexes of Le with MnII, CuII, ZnII, and CdII was investigated in aqueous solution by using potentiometric and spectrophotometric titration experiments. Extended equilibrium systems comprising a large number of species were observed, such as [M(Le)]2+, protonated complexes [MHz(Le)]2+z and oligonuclear aggregates. The pKa values of H6(Le)6+ (25 °C, μ=0.10 m ) were found to be 2.99, 5.63, 6.72, 7.38, 8.37, and 9.07, and the determined formation constants (log β) of [M(Le)]2+ were 6.13(3) (MnII), 20.11(2) (CuII), 13.60(2) (ZnII), and 10.43(2) (CdII). The redox potentials (vs. NHE) of the [M(Le)]3+/2+ couples were elucidated for Co (?0.38 V) and Ni (+0.90 V) by cyclic voltammetry.  相似文献   

12.
Several salts containing the cation Co(penten)3+, in which the hexamin «penten» (formula: page 625) acts as a sexadentate ligand, have been synthesized and characterized. Its optical antipodes have been separated in some of the salts (Fig. 4), and the rate of racemization studied. In strongly alkaline solution one of the 5 chelate rings slowly opens and Co(penten)OH2+ is produced (Fig. 1), to which a first proton can be attached at the terminal NH2-group (→ Co(Hpenten)OH3+), and a second which converts the hydroxo-complex into the aquo-complex (→ Co(Hpenten)OH4+). The equilibria between Co(penten)3+, Co(penten)OH2+, Co(Hpenten)OH3+ and Co-(Hpenten)OH24+ have been elucidated, and the kinetics of the ring opening and ring closing reactions have been studied. Ring opening and ring closure take place with retention of configuration. It proved impossible to open two of the chelate rings of Co(penten)3+. Cristalline salts with cations of the general formula Co(penten)X3?λ or Co (Hpeten)X4?λ, with Xλ? ? OH?, H2O, F?, Cl?, Br?, J?, SCN?, NO2,? and CO32?, have been obtained and characterized (Fig. 1, 2, 7 and Table 1).  相似文献   

13.
Properties indirectly determined, or alluded to, in previous publications on the titled isomers have been measured, and the results generally support the earlier conclusions. Thus, the common five‐coordinate intermediate generated in the OH?‐catalyzed hydrolysis of exo‐ and endo‐[Co(dien)(dapo)X]2+ (X=Cl, ONO2) has the same properties as that generated in the rapid spontaneous loss of OH? from exo‐ and endo‐[Co(dien)(dapo)OH]2+ (40±2% endo‐OH, 60±2% exo‐OH) and an unusually large capacity for capturing (R=[CoN3]/[CoOH][]=1.3; exo‐[CoN3]/endo‐[CoN3]=2.1±0.1). Solvent exchange for spontaneous loss of OH? from exo‐[Co(dien)(dapo)OH]2+ has been measured at 0.04 s?1 (k1, 0.50M NaClO4, 25°) from which similar loss from the endo‐OH isomer may be calculated as 0.24 s?1 (k2). The OH?‐catalyzed reactions of exo‐ and endo‐[Co(dien)(dapo)N3]2+ result in both hydrolysis of coordinated via an OH?‐limiting process =153 M ?1 s?1; =295 M ?1 s?1; KH=1.3±0.1 M ?1; 0.50M NaClO4, 25.0°) and direct epimerization between the two reactants =33 M ?1 s?1; =110 M ?1 s?1; 1.0M NaClO4, 25.0°). Comparisons are made with other rapidly reacting CoIII‐acido systems.  相似文献   

14.
The oxidation processes of a Pt(111) electrode in alkaline electrolytes depend on non‐specifically adsorbed ions according to in situ X‐ray diffraction and infrared spectroscopic measurements. In an aqueous solution of LiOH, an OHad adlayer is formed in the first oxidation step of the Pt(111) electrode as a result of the strong interaction between Li+ and OHad, whereas Pt oxidation proceeds without OHad formation in CsOH solution. Structural analysis by X‐ray diffraction indicates that Li+ is strongly protective against surface roughening caused by subsurface oxidation. Although Cs+ is situated near the Pt surface, the weak protective effect of Cs+ results in irreversible surface roughening due to subsurface oxidation.  相似文献   

15.
A nickel(II) porphyrin Ni‐P (P=porphyrin) bearing four meso‐C6F5 groups to improve solubility and activity was used to explore different hydrogen‐evolution‐reaction (HER) mechanisms. Doubly reduced Ni‐P ([ Ni‐P ]2?) was involved in H2 production from acetic acid, whereas a singly reduced species ([ Ni‐P ]?) initiated HER with stronger trifluoroacetic acid (TFA). High activity and stability of Ni‐P were observed in catalysis, with a remarkable ic/ip value of 77 with TFA at a scan rate of 100 mV s?1 and 20 °C. Electrochemical, stopped‐flow, and theoretical studies indicated that a hydride species [H‐ Ni‐P ] is formed by oxidative protonation of [ Ni‐P ]?. Subsequent rapid bimetallic homolysis to give H2 and Ni‐P is probably involved in the catalytic cycle. HER cycling through this one‐electron‐reduction and homolysis mechanism has been proposed previously but rarely validated. The present results could thus have broad implications for the design of new exquisite cycles for H2 generation.  相似文献   

16.
TiO2 Co nanotubes decorated with nanodots (TiO2 NDs/Co NSNTs‐CFs) are reported as high‐performance earth‐abundant electrocatalysts for the hydrogen evolution reaction (HER) in alkaline solution. TiO2 NDs/Co NSNTs can promote water adsorption and optimize the free energy of hydrogen adsorption. More importantly, the absorbed water can be easily activated in the presence of the TiO2–Co hybrid structure. These advantages will significantly promote HER. TiO2 NDs/Co NSNTs‐CFs as electrocatalysts show a high catalytic performance towards HER in alkaline solution. This study will open up a new avenue for designing and fabricating low‐cost high‐performance HER catalysts.  相似文献   

17.
The perovskite SrNb0.1Co0.7Fe0.2O3?δ (SNCF) is a promising OER electrocatalyst for the oxygen evolution reaction (OER), with remarkable activity and stability in alkaline solutions. This catalyst exhibits a higher intrinsic OER activity, a smaller Tafel slope and better stability than the state‐of‐the‐art precious‐metal IrO2 catalyst and the well‐known BSCF perovskite. The mass activity and stability are further improved by ball milling. Several factors including the optimized eg orbital filling, good ionic and charge transfer abilities, as well as high OH? adsorption and O2 desorption capabilities possibly contribute to the excellent OER activity.  相似文献   

18.
We report a novel modulation strategy by introducing transition metals into NiS2 nanosheets (NSs) to flexibly optimize the electronic configurations and atomic arrangement. The Co‐NiS2 NSs exhibit excellent hydrogen evolution reaction (HER) performance with an overpotential of 80 mV at j=10 mA cm?2 and long‐term stability of 90 h in alkaline media. The turnover frequencies (TOFs) of 0.55 and 4.1 s?1 at an overpotential of 100 and 200 mV also confirm their remarkable performance. DFT calculations reveal that the surface dopants abnormally sensitize surface Ni‐3d bands in the long‐range order towards higher electron‐transfer activity, acting as the electron‐depletion center. Meanwhile, the high lying surface S‐sites possess substantially high selectivity for splitting the adsorbing H2O that guarantee the high HER performance within alkaline conditions. This work opens opportunities for enhancing water splitting by atomic‐arrangement‐assisted electronic modulation via a facile doping strategy.  相似文献   

19.
The practical application of layered black phosphorus (LBP) is compromised by fast decomposition in the presence of H2O and/or O2. The role of H2O is controversial. Herein, we propose a hydroxide ion (OH?)‐initiated degradation mechanism for LBP to elucidate the role of H2O. We found that LBP degraded faster in alkaline solutions than in neutral or acidic solutions with or without O2. Degradation rates of LBP increased linearly from pH 4 to 10. Density functional theory (DFT) calculations showed that OH? initiated the decomposition of LBP through breaking the P?P bond and forming a P?O bond. The detection of hypophosphite, generated from OH? reacting with P atoms, confirmed the hypothesis. Protons acted in a way distinctive from OH?, by inducing deposition/aggregation or forming a cation–π layer to protect LBP from degradation. This work reveals the degradation mechanism of LBP and thus facilitates the development of effective stabilization technologies.  相似文献   

20.
The superior properties of nanomaterials with a special structure can provide prospects for highly efficient water splitting and lithium storage. Herein, we fabricated a series of peapodlike C@Ni2?xCoxP (x≤1) nanocomposites by an anion‐exchange pathway. The experimental results indicated that the HER activity of C@Ni2?xCoxP catalyst is strongly related to the Co/Ni ratio, and the C@NiCoP got the highest HER activity with low onset potential of ~45 mV, small Tafel slope of ~43 mV dec?1, large exchange current density of 0.21 mA cm?2, and high long‐term durability (60 h) in 0.5 m H2SO4 solutions. Equally importantly, as an anode electrode for lithium batteries, this peapodlike C@NiCoP nanocomposite gives excellent charge–discharge properties (e.g., specific capacity of 670 mAh g?1 at 0.2 A g?1 after 350 cycles, and a reversible capacity of 405 mAh g?1 at a high current rate of 10 A g?1). The outstanding performance of C@NiCoP in HER and LIBs could be attributed to the synergistic effect of the rational design of peapodlike nanostructures and the introduction of Co element.  相似文献   

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