Surface modification of carbon materials and its application as adsorbents

Phosphorus-oxygen groups drive surface-confined growth of high-valence amorphous transition-metal oxides on carbon surface for oxygen evolution reaction

Beyond the morphological study, the key to optimizing the performance of carbon-supported oxides in oxygen evolution reaction (OER) lies in phase engineering and electronic structure regulation. In this study, the surface-confined growth of high-valence amorphous transition-metal oxides on carbon surface is achieved by introducing phosphorus-oxygen groups, which strongly adsorb transition-metal ions and inhibit atomic rearrangement during heat treatment. Experimental characterization revealed that the oxides remained amorphous over a wide temperature range (up to 550 °C). Density functional theory (DFT) calculations and electronic structure analysis revealed the high electron-withdrawing capacity of the phosphorus-oxygen groups, which led to an increase in the valence state of transition metals. The obtained catalysts show excellent OER performance due to the matched OH- adsorption and deprotonation, requiring an overpotential of 251 mV to reach 10 mA cm-2. This study highlights the importance of phase engineering and electronic structure regulation in designing carbon-supported oxides, providing a universal method to achieve amorphization and electronic modulation of transition-metal oxides.

Two-dimensional nanomaterial MXenes for efficient gas separation: a review

Transition metal carbides/nitrides (MXenes) are emerging two-dimensional (2D) materials that have been widely investigated in recent years. In general, these materials can be obtained from MAX phase ceramics after intercalation, etching, and exfoliation to obtain multilayer MXene nanosheet structures; moreover, they have abundant end-group functional groups on their surface. In recent years, the excellent high permeability, fine sieving ability and diverse processability of MXene series materials make the membranes prepared using them particularly suitable for membrane-based separation processes in the field of gas separation. 2D membranes enhance the diversity of the pristine membrane transport channels by regulating the gas transport channels through in-plane pores (intrinsic defects), in-plane slit-like pores, and planar to planar interlayer channels, endowing the membrane with the ability to effectively sieve gas energy efficiently. Herein, we review MXenes, a class of 2D nanomaterials, in terms of their unique structure, synthesis method, functionalization method, and the structure-property relationship of MXene-based gas separation membranes and list examples of MXene-based membranes used in the field of gas separation. By summarizing and analyzing the basic properties of MXenes and demonstrating their unique advantages compared to other 2D nanomaterials, we lay a foundation for the discussion of MXene-based membranes with outstanding carbon dioxide (CO₂) capture performance and outline and exemplify the excellent separation performances of MXene-based gas separation membranes. Finally, the challenges associated with MXenes are briefly discussed and an outlook on the promising future of MXene-based membranes is presented. It is expected that this review will provide new insights and important guidance for future research on MXene materials in the field of gas separation.