Multifunctional steel surface through the treatment with graphene and h-BN

The search for improved surface properties of engineering alloys is always a matter of interest. Herein, we introduce a surface treatment based on depositing a non-continuous layer of two-dimensional (2D) nanomaterials via a simple and scalable method. 2D nanosheets of hexagonal boron nitride (h-BN) and graphene nanoplatelets (GNP) were sprayed on mild steel, followed by mild heat treatment. The nanosheets are strongly attached to the surfaces and even diffused to submicron under the surface, as proved by various analytical techniques. The mechanical, tribological and corrosion evaluations show significant simultaneous enhancement in a set of surface properties. From the friction tests with sliding steel-steel tribo-pairs under dry conditions, the graphene treatment decreases the friction coefficient and wear area by 21% and 31%, respectively. Interestingly, it is revealed that under dry and lubricated conditions, graphene-doped h-BN exhibits outstanding anti-wear properties synergistically compared to stand-alone 2D materials. The possible wear mechanism is investigated and found to be based on the formation of a tribofilm

2D mica as a new additive for nanolubricants with high tribological performance

This article presents 2D mica nanoplatelets as a novel additive to produce a stable engine lubricant. The planar structure and excellent mechanical properties of 2D mica contribute significantly to the improvements in tribological performance when evaluated under pure sliding and rolling/sliding contact configurations. The wear rate is reduced by 72 %, and the coefficient of friction (COF) decreases by 28 % when 2D mica is added to engine oil under pure sliding conditions. No tribological improvement was observed under rolling/sliding conditions. Our results also showed that nanosheet loading plays a significant role in nanolubricant performance, where 0.2 wt% is the optimum. These findings demonstrate superior performance to other 2D material nanoadditives and indicate the potential for commercial applications of 2D mica-based nanolubricants

Sustainable regeneration of high-performance LiCoO2 from completely failed lithium-ion batteries

Utilising the solid-state synthesis method is an easy and effective way to recycle spent lithium-ion batteries. However, verifying its direct repair effects on completely exhausting cathode materials is necessary. In this work, the optimal conditions for direct repair of completely failed cathode materials by solid-state synthesis are explored. The discharge capacity of spent LiCoO2 cathode material is recovered from 21.7 mAh g−1 to 138.9 mAh g−1 under the optimal regeneration conditions of 850 °C and n(Li)/n(Co) ratio of 1:1. The regenerated materials show excellent electrochemical performance, even greater than the commercial LiCoO2. In addition, based on the whole closed-loop recycling process, the economic and environmental effects of various recycling techniques and raw materials used in the battery production process are assessed, confirming the superior economic and environmental feasibility of direct regeneration method

Transforming Nature's Bath Sponge into Stacking Faults-Enhanced Ag Nanorings-Decorated Catalyst for Hydrogen Evolution Reaction.

The rational design of cost-effective and efficient electrocatalysts for electrochemical water splitting is essential for green hydrogen production. Utilizing nanocatalysts with abundant active sites, high surface area, and deliberate stacking faults is a promising approach for enhancing catalytic efficiency. In this study, we report a simple strategy to synthesize a highly efficient electrocatalyst for the hydrogen evolution reaction (HER) using carbonized luffa cylindrica as a conductive N-doped carbon skeleton decorated with Ag nanorings that are activated by introducing stacking faults. The introduction of stacking faults and the resulting tensile strain into the Ag nanorings results in a significant decrease in the HER overpotential, enabling the use of Ag as an efficient HER electrocatalyst. Our findings demonstrate that manipulating the crystal properties of electrocatalysts, even for materials with intrinsically poor catalytic activity such as Ag, can result in highly efficient catalysts. Further, applying a conductive carbon backbone can lower the quantities of metal needed without compromising the HER activity. This approach opens up new avenues for designing high-performance electrocatalysts with very low metallic content, which could significantly impact the development of sustainable and cost-effective electrochemical water-splitting systems

The electrochemical performance of various NiCo<inf>2</inf>O<inf>4</inf> nanostructures in hybrid supercapacitors: Investigating the impact of crystalline defects

Binary metal oxides exhibit a compelling combination of features that make them highly attractive electrode materials for supercapacitors. Herein, a facile hydrothermal method is employed for the preparation of defect-rich hierarchical nanostructured NiCo2O4 with various morphologies, including urchin-like nanostructure, nanoflowers, and 2D nanosheets; and their electrochemical performances as electrodes for hybrid supercapacitor are studies. Notably, the supercapacitor based on the urchin-like nanostructure with high oxygen vacancies delivers a high gravimetric energy density of 45.2 Wh/kg at the power density of 750 W/kg, maintaining remarkable cycling stability. The electrode exhibits specific capacitance of 423.9 and 292.0 F/g at the current density of 1.5 and 7.5 A/g, respectively, with high capacitive retention of ≈ 94 % after 1500 cycles. Crystalline defects identified in nanostructured NiCo2O4 are suggested to significantly contribute to the high ionic/electrical conductivity and the electrochemical stability of the electrodes