Periodically patterned MoS2/TiO2 heterostructures were rationally designed as nonmetal plasmonic photocatalysts for highly efficient hydrogen evolution.

Carbon nitride (g-C 3 N 4 ) materials are electroactivated for oxygen reduction (ORR) and oxygen evolution (OER) reactions when they are supported by conductive carbons. However, the electrocatalytic process on semiconductor-based heterostructures such as carbon-supported g-C 3 N 4 still suffers from a huge energy loss because of poor electron mobility. Here, we demonstrated a concept that the conjugation of g-C 3 N 4 with crystalline carbon can improve the in-plane electron mobility and make interior triazine units more electro-active for ORR and OER. As a result, the Co metal coordinated g-C 3 N 4 with crystalline carbons (Co− C 3 N 4 /C) showed a remarkable electrocatalytic performance toward both ORR and OER. For example, it displayed an onset potential of 0.95 V for ORR and an overpotential of 1.65 V for OER at 10 mA cm −2 , which are comparable and even better than those of benchmark Pt, RuO 2 , and other carbon nitride-based electrocatalysts. As a proof-of-concept application, we employed this catalyst as an air electrode in the rechargeable aluminum-air battery, which showed more rechargeable and practicable than those of Pt/C and RuO 2 catalysts in two-electrode coin battery. The characterization results identified that the good performance of Co−C 3 N 4 /C was primarily attributed to the enhanced in-plane electron mobility by crystalline carbon conjugation and the Co-coordinated g-C 3 N 4 along with nitrogen-doped carbons.

efficient and earth-abundant catalysts have been successfully developed including nitrogen-doped carbon materials that possess promising electrocatalytic performance for ORR and OER. [6][7][8][9][10] However, it remains challenging for nitrogen-doped carbon materials to achieve competitive performance to precious metal catalysts due to low nitrogen concentration.Graphitic carbon nitrides (g-C 3 N 4 ) have shown promising performance to replace nitrogen-doped carbon as a highly efficient catalyst, owing to its ultrahigh nitrogen content (theoretically estimated to be ≈60%) and easily tailored structure. [11][12][13][14][15] It is also well-known that the electrocatalytic performance is determined by catalyst structure and accessibility of active sites. It is of significant importance to maximize the electrochemical surface area to better facilitate the transport of reactants (OH − and O 2 ), and therefore enhance catalytic activity. [16][17][18] For this aim, various methods have been reported in preparation of porous g-C 3 N 4 . Conventionally, rigid templates (SiO 2 , Al 2 O 3 , and ZnO) are used to fabricate porous g-C 3 N 4 , [19,20] which can effectively improve accessibility and catalytic activity of g-C 3 N 4 . However, these rigid template-based synthesis methods are complicated, involving several steps such as template formation, template dispersion, template removal, and catalyst purification. These time-consuming processes increase the fabrication cost and can even damage the g-C 3 N 4 active sites during template removal by the use of strong acidic or basic etching. Addressing these challenges will require facile and strategic developments to synthesize porous g-C 3 N 4 without using templates.Herein, we developed a top-down and template-free strategy for the fabrication of porous g-C 3 N 4 (PCN) by controlled pyrolysis of Co 2+ /melamine networks in O 2 atmosphere. After mixing PCN with graphene oxide (GO) and thermal treating in sulfur atmosphere, CoS x @PCN/rGO catalyst was synthesized. The developed CoS x @PCN/rGO catalyst exhibited outstanding electrocatalytic activity and stability toward both OER and ORR. The CoS x @PCN/rGO also showed long cyclability as an air electrode in a zinc-air battery system, outperforming Pt and other precious metal electrocatalysts. The remarkable electrocatalytic performance of CoS x @PCN/rGO is attributed to the internally accessible nitrogen sites and the facilitated transport of intermediates in the porous structure.A typical synthesis route of PCN is schematically depicted in Figure 1a: First, cobalt(II) nitrate hexahydrate was mixed with Porous carbon nitride (PCN) composites are fabricated using a top-down strategy, followed by additions of graphene and CoS x nanoparticles. This subsequently enhances conductivity and catalytic activity of PCN (abbreviated as CoS x @PCN/rGO) and is achieved by one-step sulfuration of PCN/ graphene oxides (GO) composite materials. As a result, the as-prepared CoS x @PCN/rGO catalysts display excellent activity and stability towa...

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We present a facile way to fabricate phosphorus and aluminum codoped nickel oxide-based nanosheets by using layered double hydroxide (AlNi-LDH) as precursors, which showed an overall water-splitting performance in alkaline solution. The codoping of phosphorus and aluminum into nickel oxide nanosheets leads to an optimum balance among surface chemical state, electrochemically active surface area, and density of active sites. As a result, it can afford a current density of 100 mA cm–2 at the overpotential of 310 mV for oxygen evolution reaction (OER) and a current density of 10 mA cm–2 at the overpotential of 138 mV for hydrogen evolution reaction (HER) in 1 M KOH. When it was used as a bifunctional catalyst in a two-electrode water-splitting device, a potential of 1.56 V was achieved at the current density of 10 mA cm–2.

high interfacial impedance between SSEs and electrodes, and relatively high fabrication cost, which impede their applications. SSEs with high ionic conductivity, wide electrochemical window and low interfacial impedance are critical in developing ASSBs with high specific energy and power density. [2,3] Currently, among various SSEs, sulfide SSEs have a Li-ion conduction capability comparable to that of organic liquid electrolytes (≈10 -2 S cm -1 at room temperature). [4][5][6][7][8][9][10] Various sulfide materials with a high Li-ion conductivity of 10 -3 -10 -2 S cm -1 at room temperature, such as Li 10 GeP 2 S 12 (LGPS), [5] Li 10 SnP 2 S 12 , [6] and Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , [7] have been investigated. Among them, a family of sulfide SSEs, lithium argyrodites Li 6 PS 5 X (X = Cl, Br), [8] are attracting more attention due to high Li-ion conductivity (e.g., Li 5.3 PS 4.3 ClBr 0.7 : 2.4 × 10 -2 S cm -1 ; [9] Li 6 PS 5 Cl (denoted as LPSCl): 3.15 × 10 -3 S cm -1 [10] ) and relatively good electrochemical compatibility. The ASSB cells using argyrodites have demonstrated good cycling and rate performance. For example, recently, a sandwiched SSE separator of LPSCl-LGPS-LPSCl has been designed to prevent the growth of Li dendrites and thus enable superior cycling performance of ASSB cells; [11] and LPSCl SSE has also been matched with the silicon anode, capable of operating with high current densities and achieving a long cycle. [12] One drawback of pressed sulfide SSE separator layers is that micro-cracks easily appear and expands during Li plating/stripping in sulfide electrolytes due to the rigidness of sulfide powders, leading to short circuit in ASSB cells. [13] Thus a thicker sulfide SSE layer (e.g., ≈0.5-1.2 mm) via pressing sulfide powder was usually used in laboratory-type cells to guarantee the long-term cycling performance of the ASSBs, [13a,b,14] but this way reduces the cell-level energy density and is detrimental to scalable fabrication. Thus, it is desired to prepare sulfide SSE membranes with a small thickness and compact structure for advanced ASSBs.To obtain a thin, free-standing sulfide SSE membrane, a soft polymeric component is often used. Recently, much progress in sulfide-polymer composite solid electrolytes (CSEs) has been made. [15][16][17][18] Among them, Luo et al. prepared a 65 µm-thick bendable sulfide SSE using LPSCl and poly(ethylene oxide) (PEO), [16] and their ASSB cell of LiNi 0.7 Co 0.2 Mn 0.1 O 2 (LiNi x Co y Mn 1-x-y O 2 , denoted as NCM)||CSE||lithium-indium All-solid-state batteries (ASSBs) using sulfide electrolytes have attracted everincreasing interest due to high ionic conductivity of the sulfides. Nevertheless, a thin, strong solid-state sulfide electrolyte membrane maintaining high ionic conductivity is highly desired for ASSBs. Here, a thin, flexible composite solid electrolyte membrane composed of argyrodite sulfide Li 6 PS 5 Cl and a polar poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) framework is prepared via an electrospinning-infil...

A room-temperature synthesis of NiFe oxyfluoride (NiFeOF) holey film, using electrochemical deposition and anodic treatments, has been developed in this work. The developed room-temperature synthetic route can preserve the fine nanoporous structure inside the holey film, providing high surface area and abundant reaction sites for electrocatalytic reactions. Both computational and experimental studies demonstrate that the developed NiFeOF holey film with highly porous structure and metal residuals can be used as a high-efficiency and bifunctional catalyst for overall water splitting. Simulation result indicates that the exposed Ni atom on the NiFeOF surface serves as the active site for water splitting. Fe doping can improve the catalytic activity of the Ni active site due to the partial charge-transfer effect of Fe3+ on Ni2+. Electrochemical performance of the NiFeOF catalyst can be experimentally further enhanced through improved electrical conductivity by the residual NiFe alloy framework inside the holey film. The synergistic combination of NiFeOF holey film properties results in a highly efficient electrochemical catalyst, showing overall water splitting.

In this work, a freestanding NiS2/FeS holey film (HF) is prepared after electrochemical anodic and chemical vapor deposition treatments. With the combination of good electrical conductivity and holey structure, the NiS2/FeS HF presents superior electrochemical performance, due to the following reasons: (i) Porous structure of HF provides a large surface area and more active sites/channels/pathways to enhance the ion/mass diffusion. Moreover, the porous structure can reduce the damage from the volumetric expansion. (ii) The as‐prepared electrode combines the current collector (residual NiFe alloy) and active materials (sulfides) together, thus reducing the resistance of the electrode. Additionally, the good conductivity of HF can improve electron transport. (iii) Sulfides are more stable as active materials than sulfur, showing only a small capacity decay while retaining high cyclability performance. This work provides a promising way to develop high energy and stable electrode for Li‐S battery.