A Universal Cross-Synthetic Strategy for Sub-10 nm Metal-Based Composites with Excellent Ion Storage Kinetics

The sub-10 nm metal-based nanomaterials (SMNs) show great potential for the electrochemical energy storage field. However, their ion storage capacity and stability suffer from severe agglomeration and interface problems. Herein, a universal strategy is reported to synthesize a wide range of SMNs (e.g., metal, nitride, oxide, and sulfides) embedded in free-standing carbon foam (SMN/FC-F) composite electrodes by crossing the interfacial confinement of NaCl self-assembly with the thermal-mechanical coupling of powder metallurgy. The pressure-enhanced NaCl self-assembly interfacial confinement is greatly beneficial to preventing SMN agglomeration and promoting SMNs embedded in FC-F which originate from the welding of carbon nanosheets. They are confirmed via a series of advanced characterizations including X-ray photoelectron spectroscopy, and spherical aberration-corrected scanning transmission electron microscopy, with theoretical computations. Benefiting from the unique structure, SMNs/FC-F delivers ultrafast and stable ion-storage kinetics. As a proof-of-concept demonstration, the MoS2 /FC-F shows excellent ion storage kinetics and superior long-term cycling performance for ion storage (e.g., Na3 V2 (PO4 )2 O2 F/C//MoS2 /FC-F sodium-ion batteries exhibit a high reversible capacity of 185 mAh g-1 at 0.5 A g-1 with a decay rate of 0.05% per cycle.). This work provides a new opportunity to design and fabricate promising SMN-based free-standing working electrodes for electrochemical energy storage and conversion applications.

Facile Synthesis of Hierarchically Porous Ni-N-C for Efficient CO2 Electroreduction to CO

The reasonable design of atomically dispersed Ni-Nx sites in porous carbon nanostructures is an efficient strategy to enhance the electrochemical CO2 reduction reaction (CO2RR) catalytic activity. In this work, atomically dispersed Ni-Nx sites on hierarchically porous carbon catalysts (HP-Ni-NC) were fabricated by a facile NaCl template-assisted pyrolysis method. The catalysts exhibit a large specific surface area and a hierarchical porous structure, facilitating the exposure of numerous active sites and the mass/electron transport during the CO2RR. Consequently, the CO Faradaic efficiency maintained over 90% in a wide potential window on the optimized HP-Ni-NC-2 catalyst. The CO partial current achieved 15.2 mA cm-2 at -0.9 V (vs reversible hydrogen electrode) in a H-cell. Furthermore, the current density can achieve 250 mA cm-2 at a cell voltage of 3.11 V in a membrane electrode assembly electrolyzer, demonstrating great promise for commercial-scale application. This study presents a facile approach to synthesizing hierarchically porous structure single-atom catalysts with superior catalytic performance toward CO2RR.

Templated-Assisted Synthesis of Structurally Ordered Intermetallic Pt3Co with Ultralow Loading Supported on 3D Porous Carbon for Oxygen Reduction Reaction

Simple and reliable mass production of platinum-based alloy catalysts with excellent activity and stability is an enormous challenge for the wide commercialization of proton-exchange membrane fuel cells (PEMFC), especially those with ultralow loading of Pt. Herein, an economical, highly durable, and efficient catalyst consisting of structurally ordered intermetallic Pt₃Co alloy nanoparticles with ultralow Pt loading (1.4 wt %) supported on hierarchically porous carbon structure (three-dimensional, 3D Pt₃Co/C) were synthesized with large-scale production by the NaCl-template-assisted approach. The obtained best sample, 3D Pt₃Co/C#1, exhibited mass activities of 11.56 and 0.70 A mg_Pt^-1 for oxygen reduction reactions (ORRs) in alkaline and acidic electrolytes, which are 60.8 and 6.4 times those of commercial Pt/C, respectively. Furthermore, the 3D Pt₃Co/C#1 exhibited excellent stability both in acidic and alkaline electrolytes, with almost no decay of the half-wave potential after 5000 potential cycles. This work proposes a new high-yielding, simple, and environmentally friendly method to fabricate excellent Pt-based alloy electrocatalysts with ultralow loading of Pt, which opens up new hopes for the development of PEMFC.

Hierarchically Porous Co/Cox My (M = P, N) as an Efficient Mott-Schottky Electrocatalyst for Oxygen Evolution in Rechargeable Zn-Air Batteries

Tailoring composition and morphology of electrocatalysts is of great importance in improving their catalytic performance. Herein, a salt-templated strategy is proposed to construct novel multicomponent Co/Co_x M_y (M = P, N) hybrids with outstanding electrocatalytic performance for the oxygen evolution reaction (OER). The obtained Co/Co_x M_y hybrids present porous sheet-like architecture consisting of many hierarchical secondary building-units. The synthetic strategy depends on a facile and effective dissolution-recrystallization-pyrolysis process under NH₃ atmosphere of the precursors, which does not involve any surfactant or long-time hydrothermal pretreatment. That is different from the conventional methods for the synthesis of hierarchical nitrides/phosphides. Benefitting from unique composition/structure-dependent merits, the Co/Co_x M_y hybrids as a typical Mott-Schottky electrocatalyst exhibit good OER performance in an alkaline medium compared with their counterparts, as evidenced by a low overpotential of 334 mV at 10 mA cm^-2 and a small Tafel slope of 79.2 mV dec^-1 , as well as superior long-term stability. More importantly, the Co/Co_x M_y +Pt/C achieves higher voltaic efficiency and several times longer cycle life than conventional RuO₂ +Pt/C catalysts in rechargeable Zn-air batteries. It is envisioned that the present work can provide a new avenue for the development of Mott-Schottky electrocatalysts for sustainable energy storage.