Superior Oxygen Reduction Reaction on Phosphorus‐Doped Carbon Dot/Graphene Aerogel for All‐Solid‐State Flexible Al–Air Batteries

Abstract

Flexible energy storage devices are highly desirable in modern portable and wearable electronics. [1,2] All-solid-state flexible batteries are of particular interest for their highly compatible assembly with the existing electronic devices. [3,4] The flexible metal-air batteries, for instance, exhibiting a theoretical energy density of 8100 Wh kg −1 , have been considered as a promising clean energy conversion source to satisfy the demand of future energy storage systems. [5] As a typical requirement of metal-air batteries, the cathodic electrode undertakes the mission of oxygen reduction reaction (ORR) and significantly determines their final discharge performance. To date, the noble metal-based electrocatalysts have been widely used as the cathodic material due to their low activation energy for ORR. [6] However, their exorbitant price and lessthan-ideal durability in alkaline solution severely limited the wholesale application in the alkaline metal-air batteries. Therefore, developing novel nonprecious catalysts with highly-efficient ORR performance attracts great research attentions.Metals, metal oxides and their composites, [7,8] metal-free carbon materials, [9] and metal-N-C family [10,11] are widely studied nonprecious catalysts for ORR. The metal-free carbon materials have drawn particular interests due to their widespread pourability and excellent durability in alkaline solution, [12,13] yet the best performance is still limited by the insufficient active sites in the original pure products. Heteroatom doping of carbon materials is a unique approach to enhance the ORR activity since it can form abundant active sites. [14,15] With this regard, phosphorus (P) exhibits more negative electronegativity and stronger electron-donating ability compared to carbon, and thus the P-doped carbon materials are considered as highly potential catalysts for aqueous metal-air batteries. [16,17] Nevertheless, currently such P-doped carbon materials still exhibit a relatively poor ORR activity compared to the commercial Pt/C catalysts, ascribing to their unsatisfied structural geometry and relatively low doping level.Recently, N, S-doped carbon dots (P-CD), where mono-heteroatoms are doped into the highly stable sp 2 -hybridized graphite structure to form the covalent bonds, have been developed as a potential carbon architecture for ORR. [18] A common problem Carbon dots have been recognized as one of the most promising candidates for the oxygen reduction reaction (ORR) in alkaline media. However, the desired ORR performance in metal-air batteries is often limited by the moderate electrocatalytic activity and the lack of a method to realize good dispersion. To address these issues, herein a biomass-deriving method is reported to achieve the in situ phosphorus doping (P-doping) of carbon dots and their simultaneous decoration onto graphene matrix. The resultant product, namely P-doped carbon dot/graphene (P-CD/G) nanocomposites, can reach an ultrahigh P-doping level for carbon nanomaterials. The P-CD/G nanocomposites are fou...

Band Alignment Engineering in Two‐Dimensional Transition Metal Dichalcogenide‐Based Heterostructures for Photodetectors

“…As discussed, graphene is a gapless and semimetallic material, which allows its broadband light absorption over a broad bandwidth from terahertz (THz) to ultraviolet (UV) wavelength. [ 35 ] Furthermore, due to the super high carrier mobility, graphene can possibly form heterojunctions with a variety of semiconductors to facilitate carrier transportation. When TMDs are combined with graphene, due to the difference of their work functions, a depletion region inside the semiconductor will be formed, and the resultant built‐in electric field at the interface can significantly facilitate the separation of the photogenerated electron–hole pairs.…”

Study of a Thin Film Aluminum-Air Battery

“…It suffices to sandwich a porous paper soaked with an alkaline electrolyte between an aluminum sheet anode and a carbon cloth or carbon paper cathode to make a functional battery. These devices offer the additional advantage of flexible geometry [4,10]. In the present work, we have built such a battery using a simple design and have studied the conditions for improving its functionality.…”

Intrinsic Structure Modification of Electrode Materials for Aqueous Metal‐Ion and Metal‐Air Batteries

“…At last, an all‐solid‐state flexible Al–air battery based on P‐CD/G nanocomposites showed a stable discharge potential of ≈1.2 V under various bending states. [ 39 ] Through a facile solution‐reaction and annealing process, the confined Co nanoparticles were successfully incorporated into the hollow N‐doped carbon nanotube arrays (HCA‐Co), which has been used as advanced air electrodes for flexible Zn–air and Al–air batteries. Profiting from the comprehensive advantages of the hollow carbon nanoarray and N‐doping, the as‐prepared HCA‐Co electrode delivered an excellent catalytic activity for both ORR and OER.…”

“…[36,37] For aqueous metal air batteries, it is necessary to develop an appropriate electrocatalyst that exhibits quick oxygen and OH − transmission without water permeation, high electrocatalytic activity for both of oxygen reduction (ORR) and oxygen evolution reactions (OER), robust structure and electrochemical stability in alkaline condition or under high potentials. [38,39] To realize these goals, great effort have devoted to improve the properties of electrodes for ARBs. For example, the nanoscale designs with high specific surface are able to prompt fine electron/ion transport channels in the electrodes, contributing to high capacity utilization and fast charging/discharging ability of ARBs.…”