It is of vital importance to design efficient and low-cost bifunctional catalysts for the electrochemical water splitting under alkaline and neutral pH conditions. In this work, we report an efficient and stable NiCo₂S₄/N, S co-doped reduced graphene oxide (NCS/NS-rGO) electrocatalyst for water splitting, in which NCS microspheres are composed of one-dimentional (1D) nanorods grown homogeneously on the surface of NS-rGOs). The synergetic effect, abundant active sites, and hybridization of NCS/NS-rGO endow their outstanding electrocatalytic performance for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in both alkaline and neutral conditions. Furthermore, NCS/NS-rGO employed as both anode and cathode in a two-electrode alkaline and neutral system electrolyzers deliver 10 mA/cm² with the low cell voltage of 1.58 V in alkaline and 1.91 V in neutral condition. These results illustrate the rational design of carbon-supported nickel-cobalt based bifunctional materials for practical water splitting over a wide pH range.

Layered double hydroxide materials with two-dimensional structures and rich diversity have proved to be very promising candidates for non-precious metal electrocatalysis of the oxygen evolution reaction. We utilized a flash nano-precipitation (FNP) synthetic strategy to produce nickel–iron layered double hydroxides with tungstate anions, which simultaneously optimizes the intrinsic and extrinsic activity of the electrocatalyst. The high-valent metal W⁶⁺ was introduced into NiFe-LDH in the form of WO₄ ²⁻, which not only increases the diversity of metal species but also optimizes the electronic structure. Furthermore, the flash nano-precipitation synthesis method used changes the morphological structure of the material and thus provides more edge active sites for the oxygen evolution reaction. This led to the fact that NiFe-WO₄-LDH prepared from FNP has excellent electrocatalytic activity compared to the pristine materials we prepared. By combining the classical theory of chemical precipitation processes, it can be found that the flash nano-precipitation synthetic strategy can achieve a certain degree of separation of nucleation and growth processes by adjusting experimental parameters. The simple, efficient and scalable flash nano-precipitation synthesis method will provide new routes for metal-based electrocatalyst materials.

Enhancing the low-temperature tolerance of electrochemical energy storage devices (e.g. supercapacitors, rechargeable batteries) in a cold climate is important for automobiles, wearable devices, and smart grids used in high-altitude areas and polar regions. Recently, supercapacitors' longevity and performance under varied temperature conditions, especially low temperature, have received widespread attention. However, until now, the sluggish ion diffusion caused by electrolyte freezing restricts the low-temperature performance and durability of supercapacitors. Herein, an innovative solid-state ion conducting ice gel (IG) with a high conductivity (1.79 × 10⁻⁴ S cm⁻¹ at −15 °C), favorable flexibility, and significant low-temperature tolerance was designed and prepared by compositing polyvinyl alcohol (PVA) and CuSO₄·5H₂O salt through ultra-fast liquid nitrogen freezing. Thereafter, a symmetrical configuration supercapacitor was assembled with two flexible electrodes and IG electrolytes. The IG electrolytes feature a distinct solid-state ion conductor that can provide efficient ion transportability to the supercapacitor at extremely cold temperatures with remarkable electrochemical performances. For example, even at −80 °C, the supercapacitor performed well with a capacitance retention rate of 91.8% after 7000 cycles. Besides, the remarkable mechanical properties derived from the IG electrolytes also endow the supercapacitor with great durability under various harsh deformations in sub-zero surroundings. This work will open up a new avenue for developing versatile solid–gel electrolytes with broad working temperature ranges under harsh conditions for portable and wearable energy storage devices.

An in situ gas-foaming strategy was presented to prepare atomic Fe anchored on N, S-codoped hierarchically ordered porous carbon (HOPC) framework. The HOPC and FeN ₄ S ₂ catalytic centers make it exhibit superb ORR and Zn–air battery properties.