Designing N-doped graphene-like supported highly dispersed bimetallic NiCoP NPs as an efficient electrocatalyst for water oxidation

Electrocatalysts with a high oxygen evolution reaction (OER) activity are very important for electrochemical water oxidation, but they are also challenging. In this study, N-doped graphene-like supported highly dispersed bimetallic NiCoP NPs as an efficient electrocatalyst for water oxidation were prepared by using cation exchange resin as a carbon source and by loading cobalt and nickel on D001 by a high-temperature calcination method. The designed electrocatalyst with bimetallic phosphide as the active center shows excellent OER catalytic performance, with an overpotential of 324 mV at 10 mA cm-2 and a corresponding Tafel slope of 97.28 mV dec-1. The increase in NiCoP-3@GL activity may be due to the increase in surface area (933.49 m2 g-1) caused by the irregular morphology, rich interface contact, and porous structure. In addition, the strong combination of NiCoP and GL improves the structural stability and durability of the electrocatalyst. After 5000 cyclic voltammetry tests, the performance of the catalyst decreased by 16.9 %. This work provides a new idea for designing efficient bimetallic phosphide electrocatalysts.

Two-Dimensional Porous Polymers: From Sandwich-like Structure to Layered Skeleton

Inorganic porous materials have long dominated the field of porous materials due to their stable structure and wide applications. In the past decade, porous polymers have generated considerable interest among researchers because of their easily tunable porosity, carbon-rich backbones, and prominent physical properties. These attributes enable porous polymers to be used in various applications such as sensing, gas separation and storage, catalysis, and energy storage. However, poor dispersibility has long hindered the development of porous polymers. A majority of the reported porous polymers can only be synthesized with amorphous structure through direct precipitation from solutions during reactions. The rational design and synthesis of porous polymers with controllable morphology, such as two-dimensional (2D) morphology, remains great challenge. Two-dimensional nanomaterials have attracted considerable interest because of their unique properties, which originate from the intrinsic chemical structures and 2D dimensionality. Among 2D nanomaterials, 2D porous polymers, which possess the advanced features of polymers, porous materials, and 2D nanomaterials, have been a rising star. Conventionally, polymerization strategies for generating 2D porous polymers mainly include the cross-linking of multiarmed monomers in 2D-space-confined environments, such as crystalline solid surfaces, liquid-liquid interfaces, and liquid-air interfaces. However, these methods always involve complicate operations, e.g., under vacuum, sophisticated equipment, film transfer technology, exfoliation, and so on and, most importantly, are difficult to scale up. To overcome this synthesis obstacle, 2D nanomaterials, such as graphene, can be used as 2D templates for synthesis of sandwich-like 2D porous polymers and porous carbon nanosheets. p-Bromobenzene-, p-cyanobenzene-, polyacrylonitrile-, and amino-functionalized graphene are used as templates for direct surface polymerization through reactions such as Sonogashira-Hagihara coupling reaction, condensation reaction, ionothermal reaction, reversible addition-fragmentation chain transfer polymerization, Friedel-Crafts reaction, and oxidation reaction. Therefore, sandwich-like 2D conjugated microporous polymers, Schiff-base type porous polymers, covalent triazine frameworks, hyper-cross-linked porous polymers, and mesoporous conducting polymers can be easily prepared. Beyond graphene, other excellent 2D nanomaterials, e.g., MoS₂, can also act 2D templates to construct 2D porous polymers and corresponding hybrid materials. In addition, 2D morphology for porous polymer can be achieved without 2D templates in a few cases. For instance, olefin-linkage-linked covalent organic frameworks can be synthesized through Knoevenagel condensation reaction. As is known, porous polymers can serve as carbon-rich precursors to generate heteroatom doped porous carbons for energy storage and catalysis. Thus, one benefit of 2D porous polymers is new access toward porous carbon nanosheets through direct pyrolysis without using inorganic porous templates. In this Account, we summarize recent research on 2D porous polymers and corresponding porous carbon nanosheets.

Polyoxometalate Compound-Derived MoP-Based Electrocatalyst with N-Doped Mesoporous Carbon as Matrix, a Cathode Material for Zn-H+ Battery

H₂ is confirmed as a perfect substitute for traditional fossil energy, which can be obtained through hydrogen evolution reaction (HER) after electrocatalytic H₂O decomposition. High-performance electrocatalysts play a significant role in HER. Here, with coordination complex-modified Standberg-type polyoxometalate and peach juice as precursors, MoP-based electrocatalysts with N-doped mesoporous carbon as a matrix (MoP@NMC) were obtained. Remarkably, during synthesis, the extremely poisonous PH₃ and highly explosive H₂ were avoided. MoP@NMC exhibits very excellent electrocatalytic activity in acidic electrolytes. To get 10 mA·cm^-2 current, MoP@NMC only requires 92 mV overpotential with Tafel slope 56 mV·dec^-1. It also possesses perfect long time stability and durability in HER. More importantly, with MoP@NMC as the cathode and the Zn plate serving as the anode, a new type of battery, Zn-H⁺ battery, is assembled. In this Zn-H⁺ battery, Zn provides electrons, which pass through an external circuit and reach the cathode. Under the catalysis of MoP@NMC, the H⁺ ions are reduced by these electrons and form H₂. The open circuit voltage of the Zn-H⁺ battery is 1.19 V. Its peak power density is 89.7 mW·cm^-2. The energy density of this Zn-H⁺ battery arrives at 809 W h·kg^-1 at 10 mA·cm^-2. This work establishes a new piece of research field for HER.

Earth-Abundant Transition-Metal-Based Electrocatalysts for Water Electrolysis to Produce Renewable Hydrogen

Fundamentals of water electrolysis, and recent research progress and trends in the development of earth-abundant first-row transition-metal (Mn, Fe, Co, Ni, Cu)-based oxygen evolution reaction (OER) and hydrogen evolution (HER) electrocatalysts working in acidic, alkaline, or neutral conditions are reviewed. The HER catalysts include mainly metal chalcogenides, metal phosphides, metal nitrides, and metal carbides. As for the OER catalysts, the basic principles of the OER catalysts in alkaline, acidic, and neutral media are introduced, followed by the review and discussion of the Ni, Co, Fe, Mn, and perovskite-type OER catalysts developed so far. The different design principles of the OER catalysts in photoelectrocatalysis and photocatalysis systems are also presented. Finally, the future research directions of electrocatalysts for water splitting, and coupling of photovoltaic (PV) panel with a water electrolyzer, so called PV-E, are given as perspectives.

Tandem MoP nanocrystals with rich grain boundaries for efficient electrocatalytic hydrogen evolution

Crystallographically interconnected MoP nanocrystals with abundant grain boundaries are facilely synthesized and they exhibit outstanding electrocatalytic activities for hydrogen evolution.

CoP for hydrogen evolution: implications from hydrogen adsorption

Synergistic adsorption of hydrogen atoms on Co and P sites of CoP(111) leads to a nearly neutral free energy of adsorption that is highly conductive to hydrogen evolution.