Carbon Dots Integrated NiCo₂O₄ Hierarchical Nanoneedle Arrays Supported on Ni Foam as Efficient and Stable Electrode for Hydrogen and Oxygen Evolution Reactions

Abstract

The production of hydrogen and oxygen via water electrolysis has become a sustainable and encouraging pathway for the establishment of new energy sources. Herein, we report the successful growth of hierarchical NiCo2O4‐carbon dots (CDs) nanoneedle arrays supported on nickel foam through a simple and environmentally benign hydrothermal self‐assembly technique. The designed material acts as a binder free electrode and shows bifunctional electrocatalytic activity for both hydrogen evolution reaction (HER) as well as oxygen evolution reaction (OER) in alkaline medium. An electrocatalyst sample with an optimal loading of CDs (25 mg) requires a low overpotential of 146 mV to achieve a current density of 10 mA/cm2 for the HER in an alkaline medium, whereas it requires an overpotential of 390 mV to achieve a current density of 50 mA/cm2 for the OER in the same alkaline medium. The excellent electrocatalytic activities of the sample with loading of CD can be ascribed due to the presence of large number of exposed active sites offered by CD/NiCo2O4 and the enhanced electron transfer processes occurring as a result of hierarchical structure composed of three‐dimensional nickel foam and the NiCo2O4−CDs nanoneedle arrays. Thus, the synthesis method introduced in this present work is a facile and cost‐effective approach for the construction of bifunctional electrocatalysts with high reactivity and excellent durability.

Bifunctional Behavior of Pd/Ni Nanocatalysts on MOF‐Derived Carbons for Alkaline Water‐splitting

“…Hydrogen (H 2 ) fuel has the potential to replace fossil fuel because it is environmentally benign and large amount can easily be obtained from water [1][2][3][4]. Electrochemical water-splitting is one of the most effective and efficient techniques employed for H 2 and oxygen (O 2 ) productions via processes: hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) [5][6][7]. Commercial water electrolyzer is used to produce H 2 , which is employed as the major fuel for alternative future energy source, mainly performed in alkaline media [4].…”

A Single Carbon-Dot System Enabling Multiple Stimuli Activated Room-Temperature Phosphorescence

“…The high-resolution TEM (HRTEM) image revealed that the lattice fringe is not clear enough, which indicates a relatively poor crystallinity characteristic of S-CDs core (Figure S1a). 32 The poor crystallinity of S-CDs was further confirmed by the selected area electron diffraction (SAED) patterns (Figure S1b). 33 Raman spectra reflected that the intensity ratio of the disordered D band at 1374 cm −1 and the crystalline G band at 1574 cm −1 (I G /I D ) was 0.89.…”

“…This conformational change is favorable for molecular aggregation and a final emission enhancement (i.e., a light-controlled aggregation-induced phosphorescence (AIP) effect). Additionally, previous literature reported that CDs can be produced by the thermal pyrolysis of raw material in strongly alkaline environment and can be synthesized by hydrothermal treatment of polycarboxylic acid compound. , …”

“…Additionally, previous literature reported that CDs can be produced by the thermal pyrolysis of raw material in strongly alkaline environment and can be synthesized by hydrothermal treatment of polycarboxylic acid compound. 31,32 Based on these considerations, in this work, we proposed a strategy for developing multiple stimuli responsive RTP on a single CD system by employing a carboxyl-modified persulfurated aromatic compound (compound 1) as the precursor. Accordingly, the S-doped carbon dots (S-CDs) were synthesized by hydrothermal treatment of compound 1 in strongly alkaline NaOH aqueous solution at 180 °C (Figure 1a).…”

Recent Progress in the Development of Advanced Functionalized Electrodes for Oxygen Evolution Reaction: An Overview

“…NiCo 2 O 4 (NC)-carbon dots (CDs) nano needle arrays have been fabricated on nickel (Ni) foam and directly used as an OER catalyst without any electrode binder [ 35 ]. Poly(vinyl pyrrolidone) were exposed to heat for 5 h at 180 °C to obtain CDs, and then different amount (5, 25 and 40 mg) of CDs were mixed with another couple of salts to generate the catalysts, and they were denoted as NCCD5, NCCD25 and NCCD40, respectively.…”