Post-transition elements, together with zinc-group metals and their alloys belong to an emerging class of materials with fascinating characteristics originating from their simultaneous metallic and liquid natures. These metals and alloys are characterised by having low melting points (i.e. between room temperature and 300 °C), making their liquid state accessible to practical applications in various fields of physical chemistry and synthesis. These materials can offer extraordinary capabilities in the synthesis of new materials, catalysis and can also enable novel applications including microfluidics, flexible electronics and drug delivery. However, surprisingly liquid metals have been somewhat neglected by the wider research community. In this review, we provide a comprehensive overview of the fundamentals underlying liquid metal research, including liquid metal synthesis, surface functionalisation and liquid metal enabled chemistry. Furthermore, we discuss phenomena that warrant further investigations in relevant fields and outline how liquid metals can contribute to exciting future applications.

Hydrogen evolution reaction (HER) in alkaline medium is currently a point of focus for sustainable development of hydrogen as an alternative clean fuel for various energy systems, but suffers from sluggish reaction kinetics due to additional water dissociation step. So, the state‐of‐the‐art catalysts performing well in acidic media lose considerable catalytic performance in alkaline media. This review summarizes the recent developments to overcome the kinetics issues of alkaline HER, synthesis of materials with modified morphologies, and electronic structures to tune the active sites and their applications as efficient catalysts for HER. It first explains the fundamentals and electrochemistry of HER and then outlines the requirements for an efficient and stable catalyst in alkaline medium. The challenges with alkaline HER and limitation with the electrocatalysts along with prospective solutions are then highlighted. It further describes the synthesis methods of advanced nanostructures based on carbon, noble, and inexpensive metals and their heterogeneous structures. These heterogeneous structures provide some ideal systems for analyzing the role of structure and synergy on alkaline HER catalysis. At the end, it provides the concluding remarks and future perspectives that can be helpful for tuning the catalysts active‐sites with improved electrochemical efficiencies in future.

We develop a simple and economical thermal annealing method for the synthesis of phosphorus-doped graphene, which exhibits remarkable electrocatalytic activity towards the oxygen reduction reaction and enhances the electrochemical performance as an anode material for lithium ion batteries. The experimental results suggest the significant role of phosphorus atoms in graphene.

Defect engineering is an effective way to modulate the electric states and provide active sites for electrocatalytic reactions. However, most studied oxygen vacancies are unstable and susceptible under the oxygen circumstance. Here, we fabricated cobalt-defected Co 3−x O 4 in situ for an efficient oxygen evolution reaction (OER). XAFS and PALS characterizations show that the crystals have abundant Co vacancies and a distorted structure. DFT calculations indicate that the metal defects lead to obvious electronic delocalization, which enhances the carrier transport to participate in water-splitting reactions along the defective conducting channels and the water adsorption/activation on the catalyst surface. Therefore, cobalt-defected Co 3−x O 4 shows remarkably high OER activity by delivering a much lower overpotential of 268 mV@ 10 mA cm −2 (with a small Tafel slope of 38.2 mV/dec) for OER in KOH electrolyte, in comparison with normal Co 3 O 4 (376 mV), IrO 2 (340 mV), and RuO 2 (276 mV). This work opens up a promising approach to construct electronic delocalization structures in metal oxides for high-performance electrochemical catalysts.

Lithium ion batteries (LIBs) possess energy densities higher than those of the conventional batteries, but their lower power densities and poor cycling lives are critical challenges for their applications to electric vehicles (EVs) or grid stations. The energy and power densities, as well as the life of LIBs are dependent on electrodes where sluggish diffusion control process and structural stability are the main concerns. Here, the lithium storage mechanism of anode materials and the Goodenough diagram to explain the potential of cell and key parameters to determine the performance of an anode are highlighted. The cost reduction parameters and the availability of anode materials for future batteries on the basis of their resources and performances will be discussed. Further, the recent progress on anode nanostructures and solutions to the associated challenges will be outlined. The use of several techniques to determine the dynamic variations in nanostructures including both structural and chemical changes of electrode nanostructures during cycling as well as the limitations for high load applications will be explained. Finally, the concluding remarks will highlight the characteristics for both anode and cathode for better choice of electrode combinations in the full batteries.

Due to their unique properties, together with their ease of synthesis and functionalization, graphene-based materials have been showing great potential in energy storage and conversion. These hybrid structures display excellent material characteristics, including high carrier mobility, faster recombination rate and long-time stability. In this review, after a short introduction to graphene and its derivatives, we summarize the recent advances in the synthesis and applications of graphene and its derivatives in the fields of energy storage (lithium ion, lithium-air, lithium-sulphur batteries and supercapacitors) and conversion (oxygen reduction reaction for fuel cells). This article further highlights the working principles and problems hindering the practical applications of graphene-based materials in lithium batteries, supercapacitors and fuel cells. Future research trends towards new methodologies to the design and the synthesis of graphene-based nanocomposite with unique architectures for electrochemical energy storage and conversion are also proposed. The Royal Society of Chemistry.

Phase-controlled nickel sulfide (Ni3 S4 and NiS1.03 ) nanoparticle (NP)/nitrogen-doped graphene (NG) composites are prepared through a facile one-pot hydrothermal process. The composites show ultrahigh capacity retentions of 98.87% and 95.94% for Ni3 S4 /NG and NiS1.03 /NG electrodes, respectively, as anode materials for lithium ion batteries.

Cobalt sulfide is a good candidate for both lithium ion batteries (LIBs) and cathodic oxygen reduction reaction (ORR), but low conductivity, poor cyclability, capacity fading, and structural changes hinder its applications. The incorporation of graphene into Co3S4 makes it a promising electrode by providing better electrochemical coupling, enhanced conductivity, fast mobility of ions and electrons, and a stabilized structure due to its elastic nature. With the objective of achieving high-performance composites, herein we report a facile hydrothermal process for growing Co3S4 nanotubes (NTs) on graphene (G) sheets. Electrochemical impedance spectroscopy (EIS) verified that graphene dramatically increases the conductivity of the composites to almost twice that of pristine Co3S4. Electrochemical measurements indicated that the as-synthesized Co3S4/G composites exhibit good cyclic stability and a high discharge capacity of 720 mA h g(-1) up to 100 cycles with 99.9% coulombic efficiency. Furthermore, the composites react with dissolved oxygen in the ORR by four- and two-electron mechanisms in both acidic and basic media with an onset potential close to that of commercial Pt/C. The stability of the composites is much higher than that of Pt/C, and exhibit high methanol tolerance. Thus, these properties endorse Co3 S4 /G composites as auspicious candidates for both LIBs and ORR.