Lian Gao

Electrolytic water splitting is a promising path for the production of clean hydrogen when combined with green electric power, such as photovoltaic and wind power; however, the high current water electrolysis is mainly dependent on the utilization of Pt, Ru, and other expensive materials, while the transition metal-based catalysts still need improvement in electrocatalytic activity and stability. Here, we present the preparation of economic and scalable electrode materials, Nickel-Iron phosphide/Nickel foam (NiFeP/NF), with a hierarchical porous structure for overall water splitting as both the anode and cathode. An overall potential of 1.85 V for the current density of 100 mA cm⁻², and a long lifetime of 700 h, were achieved by using NiFeP/NF as both the anode and cathode. The nanostructures of the composite phosphides were investigated and the spent electrode after long-term electrolysis was characterized to investigate the long-term failure mechanism of the phosphides. Surface shedding and reconstruction theories were proposed for the failure of the NiFeP/NF cathode and anode in long-term electrolysis, respectively. Furthermore, TiO₂ coating was proved to be an efficient strategy to elongate the lifetime of the phosphide electrodes, which shows a slow current decline rate of 0.49 mA·cm⁻² h⁻¹.

It is of practical importance to develop efficient non‐precious metal hydrogen‐evolving catalysts for cost‐effective sustainable hydrogen production from water. In recent years, constructing single‐atomic catalysts (SACs) has been demonstrated to be an efficacious way to boost the catalytic activity of hydrogen evolution reaction (HER) catalysts, although most of them are based on noble metals. Very recently, great advances have been achieved in noble metal‐free SACs by design of compatible material systems and implementation of novel synthetic strategies, which are determinative for the amount and pattern of metallic single atoms to be anchored on the supports and consequently the electronic states and coordination environment of the atoms. This progress report summarizes perspectives of compositions of the SACs with appropriate synthetic methods, and their relationships with the HER catalytic performance. In addition, some state‐of‐the‐art technologies, for example, in situ techniques, high throughput techniques, and machine learning, are suggested to help the design, preparation, and characterization of SACs.

Integrating with conducting polymer (CP) is one of the effective ways to enhance the capacitive properties for MoS₂ except for the controllable preparation of ultrathin MoS₂ nanosheets or appropriate phase. However, most of the MoS₂/CP composites are synthesized by traditional chemical method, in which way the structural optimization of MoS₂ is limited. Here, a facile electrochemical method is demonstrated to optimize MoS₂ by spatial‐confinement‐induced polypyrrole (PPy) anchoring. Compared with MoS₂/PPy (MP) nanocomposites synthesized by chemical method, the electrochemical prepared possesses a concomitant MoS₂ monolayer, together with a transition from semiconductor phase (2H‐MoS₂) to metallic phase (1T‐MoS₂) during the PPy coating. Consequently, the resultant MP nanocomposite shows a remarkable capacitive performance with a high capacitance of 613 F g⁻¹ at a current density of 1 A g⁻¹. Meanwhile, it possesses a good rate capability that the specific capacitance retains 74%, as the current density is increased to 10 A g⁻¹. The outstanding capacitive performance should be attributed to the existence of 1T‐MoS₂ monolayer and ultrathin PPy layer as well as their effective contacts.

Inspired by the structure of pomegranates, an intriguing pomegranate-like microflower (PM-Ni_xS_y) confining core–shell binary nickel sulfide (β-NiS/Ni₃S₄) nanobeads has been constructed for the first time, which contributes to breaking through the bottleneck of poor cycle performance for nickel sulfide-based supercapacitors (SCs). The PM-Ni_xS_y microflowers possess an open nano–micro-structure, in which the core–shell binary Ni_xS_y nanobeads are well confined in the compartment of three-dimensional (3D) graphene flowers, endowing them with robust structural integrity. Profiting from the unique structure, the PM-Ni_xS_y microflowers deliver a high specific capacity of 323.8 mA h g⁻¹ at 2 A g⁻¹ and maintain a capacity retention up to 98.9% even after 100 000 cycles. PM-Ni_xS_y//PG asymmetric supercapacitors (ASCs) are assembled and achieve an attractive energy density of 88 W h kg⁻¹ at a power density of 810 W kg⁻¹. More importantly, 97.6% of the initial capacitance is still retained even after 100 000 cycles at 5 A g⁻¹ for PM-Ni_xS_y//PG ASCs, displaying their unprecedented durable cycling life. On this basis, ASCs can be recharged by sustainable solar energy and repeatedly supply power to various electronics without a decline of electrochemical performance. Therefore, this work presents a facile route to design a pomegranate-like microflower for SCs with durable cycling performance that can be applied to store sustainable energy.

Energy‐dense supercapacitors (SCs) based on metal oxides@graphene electrode and ionic liquid (IL) electrolyte hold great promise in sustainable energy system. However, these types of SCs suffer from poor cycling stability, especially at high working voltage. Herein, a porous ferric oxide/graphene (P−Fe₂O₃/G) electrode has been developed, in which Fe₂O₃ nanoparticles exhibit abundant and suitable mesoporous channels. This structure ensures the high ionic diffusion kinetics of the IL ions during the repeated charging‐discharging processes, thereby providing the P−Fe₂O₃/G electrode with outastanding capacitance behavior and cycling performance in IL electrolyte. As a result, an ingenious asymmetric electrode concept has been put forward to fabricate energy‐dense SCs based on this P−Fe₂O₃/G as negative electrode, carbon dodecahedrons/graphene (CDs/G) as positive electrode and IL electrolyte. Remarkably, the fabricated devices exhibit superior high‐voltage cycling stability with 95 % retention after 20 000 cycles, which are much better than that of most previously reported SCs based on metal oxides/graphene electrode and IL electrolyte. On this basis, a sustainable energy system combining wind harvesting with asymmetric SCs has been established, wherein the asymmetric SCs can be effectively recharged by harvesting sustainable wind power and repeatedly supply power without decline of electrochemical performance. Therefore, this work can provide a promising porous electrode for high performance SCs in sustainable energy system.

A unique three dimensional (3D) hierarchical microcapsule structure (NiS_x@NCV) has been put forward, which is realized by the ensemble of N-doped carbon vesicles encapsulating dual-NiS_x (α-NiS/NiS₂) nanoparticles via an in situ nanospace-confined pyrolysis strategy.

Wire-shaped supercapacitors (SCs) based on shape memory materials are of considerable interest for next-generation portable and wearable electronics. However, the bottleneck in this field is how to develop the devices with excellent electrochemical performance while well-maintaining recoverability and flexibility. Herein, a unique asymmetric electrode concept is put forward to fabricate smart wire-shaped SCs with ultrahigh energy density, which is realized by using porous carbon dodecahedra coated on NiTi alloy wire and flexible graphene fiber as yarn electrodes. Notably, the wire-shaped SCs not only exhibit high flexibility that can be readily woven into real clothing but also represent the available recoverable ability. When irreversible plastic deformations happen, the deformed shape of the devices can automatically resume the initial predesigned shape in a warm environment (about 35 °C). More importantly, the wire-shaped SCs act as efficient energy storage devices, which display high volumetric energy density (8.9 mWh/cm³), volumetric power density (1080 mW/cm³), strong durability in multiple mechanical states, and steady electrochemical behavior after repeated shape recovery processes. Considering their relative facile fabrication technology and excellent electrochemical performance, this asymmetric electrode strategy produced smart wire-shaped supercapacitors desirable for multifunctional portable and wearable electronics.

Wind power harvesting in conjunction with supercapacitors (SCs) has attracted considerable attention. Nevertheless, the bottleneck in this field is how to develop SCs with low electrical resistance and high energy density. Herein, an ingenious strategy to integrate wind power harvesting and asymmetric wire‐shaped SCs (WSSCs) has been put forward for the first time. Remarkably, the asymmetric WSSCs are realized by using vertical FeOOH and CoNi₂S₄ nanosheet‐array‐coated flexible carbon fibers as negative and positive yarn electrodes, in which a vertically oriented and cross‐linked porous network, formed by electroactive nanosheet arrays, facilitates ionic diffusion and charge transport. Benefiting from an intriguing configuration, these asymmetric WSSCs, with superior flexibility and weavability, act as efficient energy storage devices, which exhibit low resistance, high volumetric energy density (3.2 mWh cm^‐3), and strong durability (91.2% after 20 000 cycles). As a result, two serial WSSCs with a high voltage of 3 V can be effectively recharged, by harvesting a sustainable wind source, and repeatedly supplying power to the lamp without decline of electrochemical performance. Therefore, this work throws light on a new avenue for the development of sustainable energy harvesting and wearable energy storage.

SiO ₂ –Ag–SiO ₂ , a sandwiched core/shell structure with a layer of Ag nanoparticles (∼4 nm) encapsulated between a shallow SiO ₂ surface layer and a SiO ₂ submicrosphere substrate (∼200 nm), has been synthesized from Ag ( NH 3 ) 2 + and SiO ₂ spheres by a facile one-pot hydrothermal method. The composite is proposed to result from the dynamic balance between the Ag ( NH 3 ) 2 + reduction and the dissolution-redeposition of SiO ₂ in mild basic media. The synthetic mechanism and the roles of the reaction time, temperature, and the amount of ammonia in the formation of this unique structure are investigated and discussed. The composite structure shows superior catalytic performance in CO oxidation to the control Ag/SiO ₂ structure prepared by impregnation. Pre-treatment by O ₂ at 600 °C significantly improves the catalytic performance of the composite structure and preserves the nanocomposite structure well.