One of the challenges to realize large‐scale water splitting is the lack of active and low‐cost electrocatalysts for its two half reactions: H2 and O2 evolution reactions (HER and OER). Herein, we ...report that cobalt‐phosphorous‐derived films (Co‐P) can act as bifunctional catalysts for overall water splitting. The as‐prepared Co‐P films exhibited remarkable catalytic performance for both HER and OER in alkaline media, with a current density of 10 mA cm−2 at overpotentials of −94 mV for HER and 345 mV for OER and Tafel slopes of 42 and 47 mV/dec, respectively. They can be employed as catalysts on both anode and cathode for overall water splitting with 100 % Faradaic efficiency, rivalling the integrated performance of Pt and IrO2. The major composition of the as‐prepared and post‐HER films are metallic cobalt and cobalt phosphide, which partially evolved to cobalt oxide during OER.
Split and polished: Electrodeposited cobalt‐phosphorous‐derived films (Co‐P) can act as superior bifunctional catalysts for overall water splitting. When employed as catalysts on both the anode and cathode for water electrolysis, the Co‐P/Co‐P catalyst couple can rival the integrated performance of IrO2 and Pt in alkaline media. Such a bifunctional Co‐P film is a promising catalyst candidate for overall water‐splitting electrolysis.
The design of active, robust, and nonprecious electrocatalysts with both H2 and O2 evolution reaction (HER and OER) activities for overall water splitting is highly desirable but remains a grand ...challenge. Herein, we report a facile two-step method to synthesize porous Co-P/NC nanopolyhedrons composed of CoP x (a mixture of CoP and Co2P) nanoparticles embedded in N-doped carbon matrices as electrocatalysts for overall water splitting. The Co-P/NC catalysts were prepared by direct carbonization of Co-based zeolitic imidazolate framework (ZIF-67) followed by phosphidation. Benefiting from the large specific surface area, controllable pore texture, and high nitrogen content of ZIF (a subclass of metal–organic frameworks), the optimal Co-P/NC showed high specific surface area of 183 m2 g–1 and large mesopores, and exhibited remarkable catalytic performance for both HER and OER in 1.0 M KOH, affording a current density of 10 mA cm–2 at low overpotentials of −154 mV for HER and 319 mV for OER, respectively. Furthermore, a Co-P/NC-based alkaline electrolyzer approached 165 mA cm–2 at 2.0 V, superior to that of Pt/IrO2 couple, along with strong stability. Various characterization techniques including X-ray absorption spectroscopy (XAS) revealed that the superior activity and strong stability of Co-P/NC originated from its 3D interconnected mesoporosity with high specific surface area, high conductivity, and synergistic effect of CoP x encapsulated within N-doped carbon matrices.
The development of high-performance nonprecious electrocatalysts with both H2 and O2 evolution reaction (HER and OER) activities for overall water splitting is highly desirable but remains a grand ...challenge. Herein, we report a facile two-step method to synthesize three-dimensional hierarchically porous urchin-like Ni2P microsphere superstructures anchored on nickel foam (Ni2P/Ni/NF) as bifunctional electrocatalysts for overall water splitting. The Ni2P/Ni/NF catalysts were prepared by template-free electrodeposition of porous nickel microspheres on nickel foam followed by phosphidation. The hierarchically macroporous superstructures with 3D configuration can reduce ion transport resistance and facilitate the diffusion of gaseous products (H2 and O2). The optimal Ni2P/Ni/NF exhibited remarkable catalytic performance and outstanding stability for both the HER and OER in alkaline electrolyte (1.0 M KOH). For the HER, Ni2P/Ni/NF afforded a current density of 10 mA cm–2 at a low overpotential of only −98 mV. When it served as an OER electrocatalyst, Ni2P/Ni/NF was partially oxidized to nickel oxides/hydroxides/oxyhydroxides (mainly NiO) on the catalyst surface and exhibited excellent OER activity with small overpotentials of 200 and 268 mV to reach 10 and 100 mA cm–2, respectively. Furthermore, when Ni2P/Ni/NF was employed as the electrocatalyst for both the cathode and anode, a water splitting electrolyzer was able to reach 10 and 100 mA cm–2 in 1.0 M KOH at cell voltages of 1.49 and 1.68 V, respectively, together with robust durability. Various characterization techniques and controlled experiments indicated that the superior activity and strong stability of Ni2P/Ni/NF for overall water splitting originated from its electrochemically active constituents, 3D interconnected porosity, and high conductivity.
Efficient, stable, and low‐cost electrocatalysts are crucial for realizing large‐scale water splitting. Herein, we report that electrodeposited nickel–phosphorous (Ni–P) films can act as efficient ...bifunctional electrocatalysts for overall water splitting. The as‐prepared Ni–P films exhibit remarkable catalytic performance for both H2 and O2 evolution reactions (HER and OER) in alkaline media, achieving a current density of 10 mA cm−2 at overpotentials of −93 mV for HER and 344 mV for OER with Tafel slopes of 43 and 49 mV dec−1, respectively, rivaling the performance of Pt and IrO2. Various techniques were employed to probe the composition and morphology of the Ni–P films prior to and post catalysis, revealing the major composition of the as‐prepared and post‐HER films as metallic nickel and nickel phosphide, which partially transform to nickel oxides during OER. It was also found that the catalytic rate of OER catalyzed by Ni–P was first order in the activity of the hydroxide anion.
Overall water splitting: Electrodeposited nickel–phosphorous films (Ni–P) function as efficient bifunctional catalysts for overall water splitting under strong alkaline conditions, rivalling the performance of the state‐of‐the‐art catalysts, Pt and IrO2.
The development of low-cost catalysts with oxygen reduction reaction (ORR) activity superior to that of Pt for fuel cells is highly desirable but remains challenging. Herein, we report a ...bimetal–organic framework (bi-MOF) self-adjusted synthesis of support-free porous Co–N–C nanopolyhedron electrocatalysts by pyrolysis of a Zn/Co bi-MOF without any post-treatments. The presence of initial Zn forms a spatial isolation of Co that suppresses its sintering during pyrolysis, and Zn evaporation also promotes the surface area of the resultant catalysts. The composition, morphology, and hence ORR activity of Co–N–C could be tuned by the Zn/Co ratio. The optimal Co–N–C exhibited remarkable ORR activity with a half-wave potential of 0.871 V versus the reversible hydrogen electrode (RHE) (30 mV more positive than that of commercial 20 wt % Pt/C) and a kinetic current density of 39.3 mA cm–2 at 0.80 V versus RHE (3.1 times that of Pt/C) in 0.1 M KOH, and excellent stability and methanol tolerance. It also demonstrated ORR activity comparable to and stability much higher than those of Pt/C in acidic and neutral electrolytes. Various characterization techniques, including X-ray absorption spectroscopy, revealed that the superior activity and strong stability of Co–N–C originated from the intense interaction between Co and N, the high content of ORR active pyridinic and pyrrolic N, and the large specific surface area.
A novel composite film based on carbon nanodots (CNDs) and chitosan was readily prepared and used as immobilization matrix to entrap a heme protein, hemoglobin (Hb) for direct electrochemistry and ...bioelectrocatalysis. A modified electrode was obtained by casting Hb–CNDs–chitosan composites on the glassy carbon (GC) electrode surface. Spectroscopic and electrochemical studies showed that Hb entrapped in the composite film remained in its native structures, and CNDs in the film can greatly facilitate DET between the protein and the GC electrode. The electron-transfer kinetics of Hb in composite film was qualitatively evaluated by using the Marcus theory, and the apparent heterogeneous electron-transfer rate constant (ks) was estimated to be 2.39(±0.03)s−1 with Laviron equations. The modified electrode showed excellent electrocatalytic behavior to the substrate, hydrogen peroxide (H2O2). The linear current response for H2O2 was from 1×10−6 to 1.18×10−4M with a detection limit of 0.27(±0.02)μM at the signal-to-noise ratio of 3, and the apparent Michaelis–Menten constant was 0.067(±0.02)mM. These important features of CNDs–chitosan film have implied to be a promising platform for elaborating bioelectrochemical devices such as biosensors and biofuel cells.
•Carbon nanodots (CNDs)-chitosan film were used as electrode materials to immobilize proteins for the first time.•CNDs–chitosan film displays good biocompatibility, conductivity, and stability.•CNDs–chitosan film provides a platform for elaborating bioelectrochemical devices.
Hollow cobalt sulfide nanoprisms obtained by a two-step, microwave-assisted synthesis within 15 min exhibit higher hydrogen evolution catalytic activity and better specific capacitance than their ...counterparts prepared by a traditional solvothermal method.
We report a planar nickel complex coordinated with a pincer-type carbene-pyridine-carbene ligand which exhibits high selectivity for electrocatalytic CO2 reduction in the presence of H2O.
A novel glassy carbon electrode (GCE) modified with carbon-spheres has been fabricated through a simple casting procedure. The modified GCE displays high selectivity and excellent electrochemical ...catalytic activities towards dopamine (DA), serotonin (5-HT), and ascorbic acid (AA). In the co-existence system, the peak separations between AA and DA, DA and 5-HT, and AA and 5-HT are large up to 230, 180, and 410 mV, respectively. Differential pulse voltammetry (DPV) has been employed to simultaneously detect DA, 5-HT, and AA, and the linear calibration curves for DA, 5-HT, and AA are obtained in the range of 20.0–150.0 μM, 40.0–750.0 μM and 300.0–2,000.0 μM with detection limits (S/N = 3) of 2.0 μM, 0.7 μM and 0.6 μM, respectively. The proposed electrode has been applied to detect DA, 5-HT, and AA in real samples using standard addition method with satisfactory results.
A novel glassy carbon electrode (GCE) modified with carbon-spheres has been fabricated through a simple casting procedure. The modified GCE displays high selectivity and excellent electrochemical ...catalytic activities towards dopamine (DA), serotonin (5-HT), and ascorbic acid (AA). In the co-existence system, the peak separations between AA and DA, DA and 5-HT, and AA and 5-HT are large up to 230, 180, and 410 mV, respectively. Differential pulse voltammetry (DPV) has been employed to simultaneously detect DA, 5-HT, and AA, and the linear calibration curves for DA, 5-HT, and AA are obtained in the range of 20.0-150.0 μM, 40.0-750.0 μM and 300.0-2,000.0 μM with detection limits (S/N = 3) of 2.0 μM, 0.7 μM and 0.6 μM, respectively. The proposed electrode has been applied to detect DA, 5-HT, and AA in real samples using standard addition method with satisfactory results.
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