Although electrocatalysts based on transition metal phosphides (TMPs) with cationic/anionic doping have been widely studied for hydrogen evolution reaction (HER), the origin of performance ...enhancement still remains elusive mainly due to the random dispersion of dopants. Herein, we report a controllable partial phosphorization strategy to generate CoP species within the Co‐based metal‐organic framework (Co‐MOF). Density functional theory calculations and experimental results reveal that the electron transfer from CoP to Co‐MOF through N‐P/N‐Co bonds could lead to the optimized adsorption energy of H2O (ΔGH2O*
) and hydrogen (ΔGH*), which, together with the unique porous structure of Co‐MOF, contributes to the remarkable HER performance with an overpotential of 49 mV at a current density of 10 mA cm−2 in 1 m phosphate buffer solution (PBS, pH 7.0). The excellent catalytic performance exceeds almost all the documented TMP‐based and non‐noble‐metal‐based electrocatalysts. In addition, the CoP/Co‐MOF hybrid also displays Pt‐like performance in 0.5 m H2SO4 and 1 m KOH, with the overpotentials of 27 and 34 mV, respectively, at a current density of 10 mA cm−2.
Co‐based MOF nanorods have been doped with CoP species through controlled partial phosphorization to promote electron transfer from CoP to Co‐MOF and achieve the optimal free energy of hydrogen adsorption. The resulting CoP/Co‐MOF hybrid exhibits extraordinary performance toward HER including pH‐universal Pt‐like activity and high stability.
Direct use of metal–organic frameworks (MOFs) with robust pore structures, large surface areas, and high density of coordinatively unsaturated metal sites as electrochemical active materials is ...highly desirable (rather than using as templates and/or precursors for high‐temperature calcination), but this is practically hindered by the poor conductivity and low accessibility of active sites in the bulk form. Herein, a universal vapor‐phase method is reported to grow well‐aligned MOFs on conductive carbon cloth (CC) by using metal hydroxyl fluorides with diverse morphologies as self‐sacrificial templates. Specifically, by further partially on‐site generating active Co3S4 species from Co ions in the echinops‐like Co‐based MOF (EC‐MOF) through a controlled vulcanization approach, the resulting Co3S4/EC‐MOF hybrid exhibits much enhanced electrocatalytic performance toward the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), with overpotentials of 84 and 226 mV required to reach a current density of 10 mA cm−2, respectively. Density functional theory (DFT) calculations and experimental results reveal that the electron transfer between Co3S4 species and EC‐MOF can decrease the electron density of the Co d‐orbital, resulting in more electrocatalytically optimized adsorption properties for Co. This study will open up a new avenue for designing highly ordered MOF‐based surface active materials for various electrochemical energy applications.
Well‐aligned metal–organic frameworks (MOFs) are synthesized through a morphology‐controlled vapor‐phase strategy. Moreover, by further partial on‐site generation of active Co3S4 species from Co ions in the Co‐based MOF through a controlled vulcanization approach, the resulting echinops‐like hybrid (Co3S4/EC‐MOF) exhibits much enhanced catalytic activity and stability toward overall water splitting.
The development of precious-metal-free electrocatalysts with high-efficiency for hydrogen evolution reaction (HER) at all pHs is of great interest for the development of electrochemical overall ...splitting technologies. Despite that intense efforts have been made to developing cost-effective electrocatalysts toward HER under both acidic and alkaline electrolytes with high efficiency, electrocatalysts with remarkable performance in neutral media are rare. Herein, N atoms doped Co2P nanorod arrays grown on carbon cloth (N–Co2P/CC) have been successfully synthesized and further used as efficient electrocatalysts for HER at all pH values. Specially, the N–Co2P/CC exhibits an overpotential of 42 mV at the current density of 10 mA cm –2 with long-term stability in 1.0 M PBS (phosphate-buffered solution), which is comparable to the benchmark Pt/CC. Density functional theory (DFT) calculations suggest nitrogen doping could tailor the electronic structure of Co2P, leading to optimized adsorption free energies of water (ΔG *H2O) and hydrogen (ΔG *H), facilitating hydrogen generation through the Volmer–Heyrovsky mechanism.
The search for active and stable bifunctional electrocatalysts toward acidic overall water splitting is under increasing demand for the development of polymer electrolyte membrane (PEM) ...electrolyzers. However, developing bifunctional electrocatalysts with Pt-like activity and superior stability under acidic media still remains a big challenge. Herein, we report a successful synthesis of Ir wavy nanowires with an ultrathin diameter of 1.7 nm through a simple wet-chemical approach. Benefiting from the unique morphology with high aspect ratios and a large specific surface area, the as-synthesized ultrathin Ir wavy nanowires exhibit enhanced activity and durability for both the oxygen evolution reaction and the hydrogen evolution reaction in acidic electrolytes. Moreover, when used for overall acidic water splitting, a current density of 10 mA cm
is achieved at only a cell voltage of 1.62 V in 0.1 M HClO
electrolyte with long-term stability. In view of the excellent electrochemical water splitting performance and superior stability in acidic electrolytes, we believe that the obtained Ir wavy nanowires could be potential alternative catalysts toward PEM water electrolysis.
Developing low-cost, highly efficient, and superior stable electrocatalysts for the oxygen evolution reaction (OER) is essential for upcoming renewable and clean energy systems. Here, 3D ternary ...nickel iron phosphide microflowers with a hierarchically porous morphology directly grown on Ni foam via a successive hydrothermal and phosphidation method are synthesized. Benefitting from their unique 3D hierarchical microflower-like structure and the strong electron interactions between Fe, Ni and P, the as-synthesized (NixFe1-x)2P catalysts can effectively catalyze the OER with an overpotential of 219 mV at a current density of 20 mA cm-2 in alkaline media, which is, to the best of our knowledge, the best among the reported non-noble metal-based catalysts.
The search for highly efficient non-precious metal electrocatalysts toward the oxygen evolution reaction (OER) is extremely essential for renewable energy systems. Here, we report the colloidal ...synthesis of Fe doped NiSe2, which functions as a high-performance electrocatalyst for the OER in alkaline solution. The NiFeSe catalysts are composed of urchin-like dendrites with a high number of active sites, which could provide fast transportation of electrons and electrolytes, and facile release of the evolved O2 bubbles during the OER catalysis. Benefitting from this unique urchin-like structure and strong electron interaction between Fe, Ni, and Se, the Ni1.12Fe0.49Se2 catalyst exhibits excellent electrocatalytic activity and high durability toward the OER in alkaline solution, with an overpotential of 227 mV at a current density of 10 mA cm-2, which is, to the best of our knowledge, higher than most of the reported selenide-based electrocatalysts.
Well-dispersed magnetically recyclable core–shell Ag@M (M = Co, Ni, Fe) nanoparticles (NPs) supported on graphene have been synthesized via a facile in situ one-step procedure, using methylamine ...borane (MeAB) as a reducing agent under ambient condition. Their catalytic activity toward hydrolysis of ammonia borane (AB) were studied. Although the Ag@Fe/graphene NPs are almost inactive, the as-prepared Ag@Co/graphene NPs are the most reactive catalysts, followed by Ag@Ni/graphene NPs. Compared with AB and NaBH4, the as-synthesized Ag@Co/graphene catalysts which reduced by MeAB exert the highest catalytic activity. Additionally, the Ag@Co NPs supported on graphene exhibit higher catalytic activity than the catalysts with other conventional supports, such as the SiO2, carbon black, and γ-Al2O3. The as-synthesized Ag@Co/graphene NPs exert satisfied catalytic activity, with the turnover frequency (TOF) value of 102.4 (mol H2 min–1 (mol Ag)−1), and the activation energy E a value of 20.03 kJ/mol. Furthermore, the as-synthesized Ag@Co/graphene NPs show good recyclability and magnetically reusability for the hydrolytic dehydrogenation of AB and MeAB, which make the practical reusing application of the catalysts more convenient. Moreover, this simple synthetic method indicates that MeAB could be used as not only a potential hydrogen storage material but also an efficient reducing agent. It can be easily extended to facile preparation of other graphene supported metal NPs.
Developing highly efficient electrocatalysts and fundamentally understanding the mechanisms for alkaline hydrogen electrode reactions, including the hydrogen oxidation reaction (HOR) and the hydrogen ...evolution reaction (HER), are highly desirable. Here we report the synthesis of the IrMo alloy nanocatalyst and its outstanding HOR/HER performances under alkaline media. Specifically, the IrMo0.59 exhibits the highest catalytic activities, which are 5 times higher than that of Ir and commercial Pt/C toward HOR and even a 10-fold enhancement toward HER. Density functional theory (DFT) calculations reveal that H2O-occupied Mo sites on the surface of IrMo could effectively optimize the free energies of *H2O and *OH, thereby enable IrMo following the so-called bifunctional mechanism both in alkaline HER/HOR electrolysis.
Ru nanoparticles supported on graphene have been synthesized via a one-step procedure using methylamine borane as reducing agent. Compared with NaBH4 and ammonia borane, the as-prepared Ru/graphene ...NPs reduced by methylamine borane exhibit superior catalytic activity towards the hydrolytic dehydrogenation of ammonia borane. Additionally, the Ru/graphene NPs exhibit higher catalytic activity than its graphene free counterparts, and retain 72% of their initial catalytic activity after 4 reaction cycles. A kinetic study shows that the catalytic hydrolysis of ammonia borane is first order with respect to Ru concentration, the turnover frequency is 100 mol H2 min−1 (mol Ru)−1. The activation energy for the hydrolysis of ammonia borane in the presence of Ru/graphene NPs has been measured to be 11.7 kJ/mol, which is the lowest value ever reported for the catalytic hydrolytic dehydrogenation of ammonia borane.
•One-step synthesize Ru NPs supported on graphene.•Using methylamine borane as reducing agent get the best catalytic activity.•Lowest activation energy value ever reported for catalytic hydrolysis of AB.
Developing highly efficient and durable electrocatalysts for overall water splitting over a wide pH range is of great interest for practical applications, but still remains a challenge. Specifically, ...to the best of our knowledge, a 3-in-1 electrocatalyst that can efficiently catalyze overall water splitting in acidic, alkaline, and neutral electrolytes has not been reported so far. Herein, we report the colloidal synthesis of well-dispersed IrW nanobranches with branch architectures and describe how the morphology varies with the amount of W doping. As expected, they exhibit outstanding catalytic performance and durability for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at all pH values, which are much higher than those of Ir nanoparticles (NPs), and most reported state-of-the-art electrocatalysts. More importantly, when further used as both an anode and cathode for overall water splitting in 0.1 M HClO4, 0.1 M KOH, and 1.0 M PBS (phosphate buffer solution), cell voltages of 1.58, 1.60, and 1.73 V, respectively, were achieved at a current density of 10 mA cm-2. The present work opens up a new avenue for designing electrocatalysts for pH-universal overall water splitting, especially for application in highly corrosive acidic media and neutral media with limited ionic concentrations.
