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The key to realizing highly efficient hydrogen production by water electrolysis is to elevate the electrocatalytic activity of the oxygen evolution reaction (OER) as a rate-determining step. Herein, we demonstrate that the electrochemical activation process of the CoP nanoflower supported on carbon cloth (CoP/CC) can remarkably reduce the OER overpotential by about 123 mV, which only requires an ultralow overpotential of 176 mV at the current density of 10 mA cm–². Correspondingly, the voltage of the assembled CoP/CC||CoP/CC electrolyzer is also greatly decreased from 1.64 to 1.49 V at 10 mA cm–². We further find that during the OER process, at least a three-step electro-oxidation process occurs on the catalyst surface in different potential ranges: under lower potentials, the ultrathin CoP nanosheets are oxidized to divalent CoO, then further oxidized to trivalent β-CoOOH under moderate potentials, and even transformed to Coᴵⱽ species under high potentials. Such produced oxidized species are favorable to the formation of OOH* active intermediates or directly serve as OOH* active intermediates of the rate-determining step, thus facilitating the OER process. Meanwhile, the generation of porous surfaces, downsizing particles, active intermediate crystal structures, and new interfaces during the OER activation process can also lower the energy barrier, further accelerating the OER process.

Developing high-efficiency and stable oxygen evolution reaction (OER) materials remains a grand challenge, especially in an acid medium. In this study, we firstly report the synthesis of phase-pure...

Iron-based oxygen reduction reaction (ORR) catalysts have been the focus of research, and iron sources play an important role for the preparation of efficient ORR catalysts. Here, we successfully use LiFePO4 as ideal sources of Fe and P to construct the heteroatom doped Fe-based carbon materials. The obtained Fe-N-P co-doped coral-like carbon nanotube arrays encapsulated Fe2P catalyst (C-ZIF/LFP) shows very high half-wave potential of 0.88 V in alkaline electrolytes toward ORR, superior to Pt/C (0.85 V), and also presents a high half-wave potential of 0.74 V in acidic electrolytes, comparable to Pt/C (0.8 V). When further applied into a home-made Zn-air battery as cathode, a peak power density of 140 mW·cm2 is reached, exceeds commercial Pt/C (110 mW·cm2). Besides, it also presents exceptional durability and methanol resistance compared with Pt/C. Noticeably, the preparation method of such a high-performance catalyst is simple and easy to optimize, suitable for the large-scale production. What’s more, it opens up a more sustainable development scenario to reduce the hazardous wastes such as LiFePO4 by directly using them for preparing high-performance ORR catalysts.

The oxygen reduction activity of carbon-based metal–N catalysts can be effectively regulated by doping with phosphorus (P). However, no attempt has been made to improve the catalyst performance by directly distributing P atoms at the active centers of Fe–N. In this work, P atoms are connected with Fe–Nx moieties in the carbon structure to form P–Fe–Nx bond by the strong electron coupling effect in a novel C–P–Fe–Nx–P–C system (CPFeNPC), verified by extended X-ray absorption fine structure (EXAFS) and X-ray photoelectron spectroscopy (XPS). As a result, it leads to an enhanced oxygen reduction performance with ultrahigh half-wave potentials of 0.923 V and 0.791 V in alkaline and acidic electrolytes, respectively. Significantly, they are far more than that of commercial Pt/C (0.854 V) under alkaline conditions and even almost the same as that of commercial Pt/C (0.807 V) under acidic conditions. Moreover, when adopted as the cathode catalyst, the assembled Zn–air battery (ZAB) and proton-exchange membrane fuel cells (PEMFCs) deliver 1.6-fold and 1.25-fold enhancements in the peak power density compared with that based on commercial Pt/C and conventional Fe–Nx–C catalysts, respectively. The developed catalysts with abundant P-coordinated Fe–Nx sites shine new light on the real application of metal–N–C catalysts in fuel cells.

Developing efficient and durable bifunctional transition metal phosphide (TMP) electrocatalysts is still a great challenge because of its relatively sluggish kinetics of oxygen evolution reaction (OER). Herein, we report a unique bimetallic diphosphide pair (FeP2–NiP2) forming spherical nanocages encapsulated in P-doped carbon layers (FeP2–NiP2@PC) as advanced bifunctional electrocatalyst synthesized by a very facile phosphorization approach. The obtained FeP2–NiP2@PC electrocatalyst exhibits an outstanding OER activity with an ultralow overpotential of 248 mV in 1 M KOH and a low overpotential of 117 mV for HER in 0.5 M H2SO4 (@10 mA·cm–2). Also it gives an exceptional long-term durability toward OER (60 h) and HER (20 h). Differently from the electrocatalysts as reported, after successive 3000 cycles CV acceleration, its overpotential decreases about 10 mV. Further investigation unveils that the electrochemical activation process boosts in situ phase transformation of oxides and phosphides to oxyhydroxi...

A series of p-type xCu2Se–SnSe (x = 0%, 0.10%, 0.15%, 0.20%, and 0.25%) composite thermoelectric materials have been prepared by the combination of ultrasonic dispersion and spark plasma sintering methods. The effects of secondary phase Cu2Se on the phase composition, microstructure, and thermoelectric properties of the composites were investigated. Microstructure characterization and elemental maps indicated Cu2Se grains uniformly distributed on the boundaries of the matrix. Transport measurements demonstrated that enhancement of the power factor and reduction of the thermal conductivity can be realized simultaneously by optimizing the adding content of Cu2Se. The highest ZT value of 0.51 at 773 K was achieved for the sample with x = 0.15%, increased by 24% compared with that of the SnSe matrix. These results demonstrate that optimizing the Cu2Se content can improve the thermoelectric performance of p-type SnSe polycrystalline materials.

Bismuth telluride zone-melting alloys are the most commercially used thermoelectric materials. However, the zone-melting ingots have weak machinability due to the strong preferred orientation. Here, non-textured graphite/Bi0.5Sb1.5Te3 (G/BST) composites were prepared by a powder metallurgy method combined with cold-pressing and annealing treatments. The composition, microstructure, and thermoelectric properties of the G/BST composites with different mass percentages of G were investigated. It was found that G addition could effectively reduce the thermal conductivity and slightly improve the electrical properties of the BST, which resulted in a large enhancement in the figure-of-merit, ZT. The largest ZT for the xG/BST composites with x = 0.05% reached 1.05 at 320 K, which is increased by 35% as compared with that of the G-free BST materials. This work provided an effective method for preparing non-textured Bi2Te3-based TE materials with a simple process, low cost, and large potential in scale production.

To improve the catalytic activity of the catalysts, it is key to intensifying the intrinsic activity of active sites or increasing the exposure of accessible active sites. In this work, an efficient oxygen reduction electrocatalyst is designed that confines plentiful FeCx nanoclusters with Fe-N4 sites in a concave porous S-N co-doped carbon matrix, readily accessible for the oxygen reduction reaction (ORR). Sulfate ions react with the carbon derived from ZIF-8 at high temperatures, leading to the shrinkage of the carbon framework and then forming a concave structure with abundant macropores and mesopores with S incorporation. Such an architecture promotes the exposure of active sites and accelerates remote mass transfer. As a result, the catalyst (Fe/S-NC) with a large number of C-S-C, Fe-N4 , and FeCx nanoclusters presents impressive ORR activity and stability. In alkaline media, the half-wave potential of the best catalyst (Fe/S2 -NC) is 0.91 V, which far exceeds that of commercial platinum carbon (0.85 V), while in acidic media the half-wave potential reaches 0.784 V, comparable to platinum carbon (0.812 V). Furthermore, for the zinc-air battery, the outstanding peak power density of Fe/S2 -NC (170 mW cm-2 ) superior to platinum carbon (108 mW cm-2 ) also highlights its great application potential.

Developing highly efficient and stable electrocatalysts plays an important role in energy‐related electrocatalysis fields. Transition‐metal phosphides (TMPs) possess a series of advantages, such as high conductivity, earth‐abundance reserves, and good physicochemical properties, therefore arousing wide attention. In this review, the electrochemical activity origin of TMPs, allowing the rational design and construction of phosphides toward various energy‐relevant reactions is first discussed. Subsequently, their unique energy‐related electrocatalysis nature toward hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), hydrogen oxidation reaction (HOR), carbon dioxide reduction reaction (CO2RR), nitrogen reduction reaction (NRR), urea oxidation reaction (UOR), methanol oxidation reaction (MOR), and others is highlighted. Then, the TMPs’ synthetic strategies are analyzed and summarized systematically. Finally, the existing key issues, countermeasures, and the future challenges of TMPs toward efficient energy‐related electrocatalysis are briefly discussed.

Exploring earth-abundant bifunctional electrocatalysts with high efficiency for water electrolysis is extremely demanding and challenging. Herein, density functional theory (DFT) predictions reveal that coupling Ni with Ni3 C can not only facilitate the oxygen evolution reaction (OER) kinetics, but also optimize the hydrogen adsorption and water adsorption energies. Experimentally, a facile strategy is designed to in situ fabricate Ni3 C nanosheets on carbon cloth (CC), and simultaneously couple with Ni nanoparticles, resulting in the formation of an integrated heterostructure catalyst (Ni-Ni3 C/CC). Benefiting from the superior intrinsic activity as well as the abundant active sites, the Ni-Ni3 C/CC electrode demonstrates excellent bifunctional electrocatalytic activities toward the OER and hydrogen evolution reaction (HER), which are superior to all the documented Ni3 C-based electrocatalysts in alkaline electrolytes. Specifically, the Ni-Ni3 C/CC catalyst exhibits the low overpotentials of only 299 mV at the current density of 20 mA cm-2 for the OER and 98 mV at 10 mA cm-2 for the HER in 1 m KOH. Furthermore, the bifunctional Ni-Ni3 C/CC catalyst can propel water electrolysis with excellent activity and nearly 100% faradic efficiency. This work highlights an easy approach for designing and constructing advanced nickel carbide-based catalysts with high activity based on the theoretical predictions.

Rational design and fabrication of nonprecious metallic multifunctional catalysts with superior performance are crucial for energy-related electrochemical devices. Herein, we report the synthesis and electrochemical properties of a sandwich-like Co@Co3O4 embedded into Fe, N, S co-doped reduced graphene oxide (Co@Co3O4/FeNS-RGO) nanocomposite catalyst. The designed Co@Co3O4/FeNS-RGO catalyst is synthesized by pyrolysis of one-pot solvothermal method-induced nano-zeolitic imidazolate framework (ZIF)/graphene oxide nanocomposite using dimethylsulfoxide as both the solvent and sulfur source. The synthesized catalyst exhibits the outstanding electrocatalytic activity in basic media for oxygen reduction reaction and oxygen evolution reactions, which outperforms the commercial Pt/C and IrO2 catalysts, respectively. In addition, the synthesized catalyst also shows a promising electrocatalytic activity towards hydrogen evolution reaction. The performance of the thus-assembled zinc-battery and the overall water-splitting device reveals that the synthesized Co@Co3O4/FeNS-RGO can be practically applied in energy-related electrochemical devices with great activity and stability.

The ability to control chemical and physical structuring at the nanometre scale is important for developing high-performance thermoelectric materials. Progress in this area has been achieved mainly by enhancing phonon scattering and consequently decreasing the thermal conductivity of the lattice through the design of either interface structures at nanometre or mesoscopic length scales or multiscale hierarchical architectures. A nanostructuring approach that enables electron transport as well as phonon transport to be manipulated could potentially lead to further enhancements in thermoelectric performance. Here we show that by embedding nanoparticles of a soft magnetic material in a thermoelectric matrix we achieve dual control of phonon- and electron-transport properties. The properties of the nanoparticles-in particular, their superparamagnetic behaviour (in which the nanoparticles can be magnetized similarly to a paramagnet under an external magnetic field)-lead to three kinds of thermoelectromagnetic effect: charge transfer from the magnetic inclusions to the matrix; multiple scattering of electrons by superparamagnetic fluctuations; and enhanced phonon scattering as a result of both the magnetic fluctuations and the nanostructures themselves. We show that together these effects can effectively manipulate electron and phonon transport at nanometre and mesoscopic length scales and thereby improve the thermoelectric performance of the resulting nanocomposites.