CoP particles embedded in N-doped two-dimensional carbon sheets as efficient electrocatalyst for water splitting

One-Step Template/Solvent-Free Pyrolysis for In Situ Immobilization of CoP Nanoparticles onto N and P Co-Doped Carbon Porous Nanosheets towards High-efficiency Electrocatalytic Hydrogen Evolution

The search for economical, active and stable electrocatalysts towards the hydrogen evolution reaction (HER) is highly imperative for the progression of water electrolysis technology and related sustainable energy conversion technologies. The delicate optimization of chemical composition and architectural configuration is paramount to design high-efficiency non-precious metal HER electrocatalysts. Herein, we report a one-step scalable template/solvent-free pyrolysis approach for in situ immobilizing uniform CoP nanoparticles onto N and P co-doped carbon porous nanosheets (denoted as CoP@N,P-CNSs hereafter). The simultaneous consideration of architectural design and nanocarbon hybridization renders the formed CoP@N,P-CNSs with plentiful well-dispersed anchored active sites, shortened pathway for mass diffusion, enhanced electric conductivity, and reinforced mechanical stability. As a consequence, the optimized CoP@N,P-CNSs exhibit an overpotential of 115 mV to afford a current density of 10 mA cm^-2 , small Tafel slope of 74.2 mV dec^-1 , high Faradaic efficiency of nearly 100 %, and superb long-term durability in an alkaline medium. Given the fabrication feasibility, mass production potential and outstanding HER performance, the CoP@N,P-CNSs may hold great promise for large-scale electrochemical water splitting. More importantly, the explored one-step template/solvent-free pyrolysis methodology offers a feasible and versatile route to fabricate carbon nanosheet-based nanocomposites for diverse energy conversation-related applications.

Coconut-Water-Mediated Carbonaceous Electrode: A Promising Eco-Friendly Material for Bifunctional Water Splitting Application

The organic and eco-friendly materials are extended to prevail over the worldwide energy crisis where bio-inspired carbonaceous electrode materials are being prepared from biogenic items and wastes. Here, coconut water is sprayed over three-dimensional (3D) nickel foam for obtaining a carbonaceous electrode material, i.e., C@Ni-F. The as-prepared C@Ni-F electrode has been used for structural elucidation and morphology evolution studies. Field emission scanning electron microscopy analysis confirms the vertically grown nanosheets of the C@Ni-F electrode, which is further employed in the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), where excellent OER and HER performances with small overpotentials of 219 and 122 mV and with stumpy Tafel slopes, i.e., 27 and 53 mV dec-1, are respectively obtained, suggesting a bifunctional potential of the sprayed electrode material. Moreover, sustainable bifunctional performance of C@Ni-F proves considerable chemical stability and moderate mechanical robustness against long-term operation, suggesting that, in addition to being a healthy drink to mankind, coconut water can also be used for water splitting applications.

N-Doped carbon-coated Co2P-supported Au nanocomposite as the anode catalyst for borohydride electrooxidation

Au₍₅₀₎Co₂P@NC₍₅₀₎/C nanoparticle composite electrocatalyst combines the lower content of noble metal and much higher catalytic activity for BH₄⁻ electrooxidation.

Surface Atom Regulation on Polyoxometalate Electrocatalyst for Simultaneous Low-Voltage H2 Production and Phenol Degradation

The electrocatalytic hydrogen evolution reaction is an ideal method for H₂ production. To improve the performance of polyoxometalate-based electrocatalyst in the hydrogen evolution reaction, one O^2- in polyoxometalate is replaced by S^2-. This weakens the binding of polyoxometalate to H*, facilitates its desorption, and improves the H₂ generation property. Vulcanized polyoxometalate only requires 55 mV to achieve 10 mA·cm^-2 current in the hydrogen evolution reaction. This electrocatalyst also exhibits promising performance in phenol degradation reaction, which is an ideal substitute for high-energy-consuming oxygen evolution reaction in H₂ production due to low voltage to drive. To acquire 100 and 200 mA·cm^-2 in the phenol degradation reaction, this vulcanized polyoxometalate only consumes 1.38 and 1.41 V. With this electrocatalyst working as a cathode and an anode simultaneously, an electrolyzer is constructed by employing phenol-containing KOH as an electrolyte. To obtain 100 and 200 mA·cm^-2 current, the electrolyzer only requires 1.54 and 1.57 V. Because energy-efficient phenol degradation reaction occurs, these values are obviously lower than the oxygen evolution reaction involved in the overall water-splitting H₂ production. This work provides a universal method to enhance the hydrogen evolution reaction (HER) activity of polyoxometalates. Furthermore, a new method is explored, which achieves energy conservation and phenol degradation simultaneously in H₂ production.

Building Polyoxometalate "Nano-Walls" on 3D Porous Carbon Paper: A Solar Steam Generation System for Water Purification

As promising fresh-water purification devices, solar steam generation systems have attracted significant attention recently. However, in practice, the approach often suffers from a poor solar energy conversion efficiency and a low water production rate due to poor material selection and inefficient microscopic structure design. Here, we fabricate an efficient solar steam generation system by "building" polyoxometalate "nano-walls" on rice paper-derived three-dimensional porous carbon paper. In this solar steam generation system, the height of the vertically aligned CoP₄ Mo₆ "nano-walls" range from 100 to 150 nm with thicknesses about 15 to 25 nm. Under 1 sun irradiation (1 sun = 1 kW m^-2 ), the surface temperature increases from 29 to 50 °C in a short time with a solar thermal conversion efficiency achieving 92.8 %. The stability and durability of this solar steam generation system, which withstands fifteen cycle continuous tests, also offer good prospects. Its attractive solar energy conversion performance originates from the intense sunlight absorption and high conversion ability of the CoP₄ Mo₆ "nano-walls", as well as extremely promising heat localization and water transportation properties of the three-dimensional porous carbon paper. This solar steam generation system, which has produced some inspiring results, is employed for seawater desalination and for purification of water polluted with organic dyes.

A binder free hierarchical mixed capacitive deionization electrode based on a polyoxometalate and polypyrrole for brackish water desalination

Capacitive deionization technology is an efficient method for brackish water desalination, in which the pseudocapacitive material plays a vital role in determining the desalination performance of the electrode directly. Compared with a traditional double-layer capacitance deionization electrode, a mixed capacitive deionization electrode possesses obvious advantages, because it integrates pseudocapacitance and double-layer capacitance together. A brand-new mixed capacitive deionization electrode is fabricated by co-deposition of P2Mo18O626- and polypyrrole on a 3D exfoliated graphite matrix using an electrochemical technique. In this electrode, composite particles composed of P2Mo18O626- and polypyrrole distribute evenly on the 3D exfoliated graphite matrix. At 1 A g-1 current, the specific capacitance of this electrode is 156.2 mA h g-1. Its rate capability is also promising with more than 76.5% of the capacitance being retained when the current increases to 20 A g-1. At 1.2 V voltage, its desalination capacity and rate reach 17.8 mg g-1 and 1.12 mg g-1 min-1 in 600 mg L-1 NaCl. This satisfactory desalination performance is attributed to the unique electrochemical properties of P2Mo18O623- and polypyrrole and the binder free character of this electrode. Even after 100 cycles, its desalination ability does not decay, which confirms its excellent stability. This work confirms the prospects for polyoxometalate based electrodes in brackish water desalination.

Metal-free multiporous carbon for electrochemical energy storage and electrocatalysis applications

An electrocatalytic and electrochemical energy storage study of biomass-derived metal-free carbon is carried out.