As the cleanest energy source, hydrogen energy is regarded as the most promising fuel. Water electrolysis, as the primary means of hydrogen production, has constantly been the focus of attention in the energy conversion field. Developing eco-friendly, cheap, safe and efficient catalysts for electrochemical water splitting (EWS) is the key challenge. Herein, the intermetallic silicide alloy is first synthesized via a facile magnesiothermic reduction and employed as bifunctional electrocatalysts for EWS. Ferric-nickel silicide (denoted as FeNiSi) alloy is designed and shows a good electrocatalytic performance for EWS. The lattice distortions of FeNiSi enhance the electrocatalytic activity. Besides, the porous structure affords more active sites and improves the reaction kinetics. As a consequence, FeNiSi delivers an excellent performance with overpotential of 308 mV for oxygen evolution reaction (OER) and 386 mV for hydrogen evolution reaction (HER) at 10 mA·cm⁻² in 1 M KOH. The stability structure of intermetallic silicide achieves an outstanding durability with an unchanged potential of 1.66 V for overall water splitting at 10 mA·cm⁻² for 15 h. This work not only provides a facile method for the synthesis of intermetallic silicide with considerable porous structures, but also develops the potential of intermetallic silicide alloy as bifunctional electrocatalysts for EWS, which opens up a new avenue for the design and application of intermetallic silicide alloy.

Aqueous rechargeable batteries are the promising energy storge technology due to their safety, low cost, and environmental friendliness. Ammonium ion (NH₄⁺) is an ideal charge carrier for such batteries because of its small hydration radius and low molar mass. In this study, VO₂·xH₂O with rich oxygen defects (d-HVO) is designed and synthesized, and it exhibits unique nanoarray structure and good electrochemical performances for NH₄⁺ storge. Experimental and calculation results indicate that oxygen defects in d-HVO can enhance the conductivity and diffusion rate of NH₄⁺, leading to improved electrochemical performances. The most significant improvement is observed in d-HVO with 2 mmol thiourea (d-HVO-2) (220 mAh·g⁻¹ at 0.1 A·g⁻¹), which has a moderate defect content. A full cell is assembled using d-HVO-2 as the anode and polyaniline (PANI) as the cathode, which shows excellent cycling stability with a capacity retention rate of 80% after 1000 cycles and outstanding power density up to 4540 W·kg⁻¹. Moreover, the flexible d-HVO-2||PANI battery, based on quasi-solid electrolyte, shows excellent flexibility under different bending conditions. This study provides a new approach for designing and developing high-performance NH₄⁺ storage electrode materials.

Rational design of oxygen evolution reaction (OER) catalysts at low cost would greatly benefit the economy. Taking advantage of earth-abundant elements Si, Co and Ni, we produce a unique-structure where cobalt-nickel silicate hydroxide [Co_2.5Ni_0.5Si₂O₅(OH)₄] is vertically grown on a reduced graphene oxide (rGO) support (CNS@rGO). This is developed as a low-cost and prospective OER catalyst. Compared to cobalt or nickel silicate hydroxide@rGO (CS@rGO and NS@rGO, respectively) nanoarrays, the bimetal CNS@rGO nanoarray exhibits impressive OER performance with an overpotential of 307 ​mV@10 ​mA ​cm⁻². This value is higher than that of CS@rGO and NS@rGO. The CNS@rGO nanoarray has an overpotential of 446 ​mV@100 ​mA ​cm⁻², about 1.4 times that of the commercial RuO₂ electrocatalyst. The achieved OER activity is superior to the state-of-the-art metal oxides/hydroxides and their derivatives. The vertically grown nanostructure and optimized metal-support electronic interactions play an indispensable role for OER performance improvement, including a fast electron transfer pathway, short proton/electron diffusion distance, more active metal centers, as well as optimized dual-atomic electron density. Taking advantage of interlay chemical regulation and the in-situ growth method, the advanced-structural CNS@rGO nanoarrays provide a new horizon to the rational and flexible design of efficient and promising OER electrocatalysts.