Novel Graphene Hydrogel/B‐Doped Graphene Quantum Dots Composites as Trifunctional Electrocatalysts for Zn−Air Batteries and Overall Water Splitting

Abstract

Herein, a facile, one‐step hydrothermal route to synthesize novel all‐carbon‐based composites composed of B‐doped graphene quantum dots anchored on a graphene hydrogel (GH‐BGQD) is demonstrated. The obtained GH‐BGQD material has a unique 3D architecture with high porosity and large specific surface area, exhibiting abundant catalytic active sites of B‐GQDs as well as enhanced electrolyte mass transport and ion diffusion. Therefore, the prepared GH‐BGQD composites exhibit a superior trifunctional electrocatalytic activity toward the oxygen reduction reaction, oxygen evolution reaction, and hydrogen evolution reaction with excellent long‐term stability and durability comparable to those of commercial Pt/C and Ir/C catalysts. A flexible solid‐state Zn–air battery using a GH‐BGQD air electrode achieves an open‐circuit voltage of 1.40 V, a stable discharge voltage of 1.23 V for 100 h, a specific capacity of 687 mAh g−1, and a peak power density of 112 mW cm−2. Also, a water electrolysis cell using GH‐BGQD electrodes delivers a current density of 10 mA cm−2 at cell voltage of 1.61 V, with remarkable stability during 70 h of operation. Finally, the trifunctional GH‐BGQD catalyst is employed for water electrolysis cell powered by the prepared Zn–air batteries, providing a new strategy for the carbon‐based multifunctional electrocatalysts for electrochemical energy devices.

Recent progress in graphene‐based electrodes for flexible batteries

“…Flexible Zn‐air batteries are more appealing compared to flexible lithium‐air batteries due to their merits of abundant resource and environmental friendliness . Similar to cathodes of lithium‐air batteries, cathodes of zinc‐air batteries should possess excellent flexibility, air permeability, high electrical conductivity, and outstanding ORR/OER electrocatalytic activity.…”

Advances of Carbon-Based Materials for Lithium Metal Anodes

“…With the development of technology, more and more new materials are recognized and applied in various fields. Graphene quantum dots (GQDs) with tiny size can be well-dispersed in the electrolyte without further modification (Deng et al, 2016;Park et al, 2016;Tam et al, 2019). Hu et al directly added GQDs to the electrolyte, which is composed of Li bis (trifluoromethane)-sulfonimide (LiTFSI, 1.0 M), 2.0 wt% LiNO 3 , 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME; 1:1 by volume) (Hu Y. et al, 2020).…”

Ultrasensitive Detection of Tetracycline Using Boron and Nitrogen Co-Doped Graphene Quantum Dots from Natural Carbon Source as the Paper-Based Nanosensing Probe in Difference Matrices

“…Furthermore, the deconvoluted C 1s spectrum ( Figure 2b Figure 2d) [25,36,37]. For O 1s species, the deconvoluted spectrum also illustrates three peaks at 533.0 (B-O), 532.1 (C-O/C-OH) and 531.8 (COOH) eV [36][37][38], Moreover, after the modification of B atom the deconvoluted C 1s and O1s spectrum show a shift peak to high binding energy (Figure 2e and 2f, respectively) compared to that for the C 1s and O 1s spectrum of pure N-GQDs ( Figure S3a,b). It means that upon doping of B into the GQDs structure, it combined with the surface functional groups as well, confirming the presence of the co-doping of N and B on GQD networks (Figure 2e).…”

“…Figure 8a displays the FTIR spectra of B,N-GQDs before and after the addition of TC. The asprepared B,N-GQDs spectrum exhibits peaks at 2950 and 1627 cm −1 , which can be considered as an indication of the C-H and C=C groups in graphene structure [31,37]. A broad peak at 3450 cm −1 is the characteristic OH bond.…”