Synthesis of CoP nanoarrays by morphological engineering for efficient electrochemical hydrogen production

Electrochemical reductive removal of trichloroacetic acids by a three-dimensional binderless carbon nanotubes/ CoP/Co foam electrode: Performance and mechanism

Numerous chlorinated disinfection by-products (DBPs) are produced during the chlorination disinfection of water. Among them, chloroacetic acids (CAAs) are of great concern due to their potential human carcinogenicity. In this study, effective electrocatalytic dechlorination of trichloroacetic acids (TCAA), a typical CAAs, was achieved in the electrochemical system with the three-dimensional (3D) self-supported CoP on cobalt foam modified by carbon nanotubes (CNT/CoP/CF) as the cathode. At a 10 mA cm-2 current density, 74.5% of TCAA (500 μg L-1) was converted into AA within 100 min. In-situ growth of CoP increased the effective electrochemical surface area of the electrode. Electrodeposited CNT promoted electron transfer from the electrode surface to TCAA. Therefore, the production of surface-adsorbed atomic hydrogen (H*) on CNT/CoP/CF was improved, further resulting in excellent electrochemical dechlorination of TCAA. The dechlorination pathway of TCAA proceeded into acetic acids via direct electronic transfer and H*-mediated reduction on CNT/CoP/CF electrode. Additionally, the electroreduction efficiency of CNT/CoP/CF for TCAA exceeded 81.22% even after 20 cycles. The highly efficient TCAA reduction performance (96.57%) in actual water revealed the potential applicability of CNT/CoP/CF in the complex water matrix. This study demonstrated that the CNT/CoP/CF is a promising non-noble metal cathode to remove chlorinated DBPs in practice.

Two birds with one stone: facile fabrication of an iron-cobalt bimetallic sulfide nanosheet-assembled nanosphere for efficient energy storage and hydrogen evolution

Transition metal sulfides are widely regarded as the most promising electrode materials for supercapacitors. Herein, we utilized a straightforward electrodeposition method to prepare an iron-cobalt bimetallic sulfide nanosheet-assembled nanosphere on nickel foam (FeCo2S4/NF). The synergistic effect between bimetals and the unique three-dimensional structure significantly improved its capacitive performance. As a result, it demonstrated a remarkable specific capacitance, brilliant long-term stability and acceptable rate capability. Moreover, FeCo2S4/NF and active carbon (AC) were used to assemble an asymmetric supercapacitor (ASC), and FeCo2S4//AC displays a maximum energy density of 29.4 W h kg-1 at 800 W kg-1. Moreover, when adopted as an electrocatalyst for the hydrogen evolution reaction (HER), FeCo2S4/NF exhibited excellent catalytic properties (η10 = 165 mV). Our research provides a valuable insight into the multidisciplinary integration of high-performance energy materials.

Constructing Molybdenum Phosphide@Cobalt Phosphide Heterostructure Nanoarrays on Nickel Foam as a Bifunctional Electrocatalyst for Enhanced Overall Water Splitting

The construction of multi-level heterostructure materials is an effective way to further the catalytic activity of catalysts. Here, we assembled self-supporting MoS₂@Co precursor nanoarrays on the support of nickel foam by coupling the hydrothermal method and electrostatic adsorption method, followed by a low-temperature phosphating strategy to obtain Mo₄P₃@CoP/NF electrode materials. The construction of the Mo₄P₃@CoP heterojunction can lead to electron transfer from the Mo₄P₃ phase to the CoP phase at the phase interface region, thereby optimizing the charge structure of the active sites. Not only that, the introduction of Mo₄P₃ will make water molecules preferentially adsorb on its surface, which will help to reduce the water molecule decomposition energy barrier of the Mo₄P₃@CoP heterojunction. Subsequently, H* overflowed to the surface of CoP to generate H₂ molecules, which finally showed a lower water molecule decomposition energy barrier and better intermediate adsorption energy. Based on this, the material shows excellent HER/OER dual-functional catalytic performance under alkaline conditions. It only needs 72 mV and 238 mV to reach 10 mA/cm² for HER and OER, respectively. Meanwhile, in a two-electrode system, only 1.54 V is needed to reach 10 mA/cm², which is even better than the commercial RuO₂/NF||Pt/C/NF electrode pair. In addition, the unique self-supporting structure design ensures unimpeded electron transmission between the loaded nanoarray and the conductive substrate. The loose porous surface design is not only conducive to the full exposure of more catalytic sites on the surface but also facilitates the smooth escape of gas after production so as to improve the utilization rate of active sites. This work has important guiding significance for the design and development of high-performance bifunctional electrolytic water catalysts.

Optimizing the electronic structure of CoNx via coupling with N-doped carbon for efficient electrochemical hydrogen evolution

Transition metal nitrides (TMNs) have been regarded as an excellent class of electrocatalysts for hydrogen evolution reaction (HER), but there is still huge room for improvement. In this work, cobalt nitride (CoN_x) coupled with N-doped carbon (NC) and supported by nickel foam (NF) is designed as an efficient HER electrocatalyst (NF/CoN_x@NC). The introduction of NC can not only optimize the electronic structure of CoN_x to boost the intrinsic activity, but also enhance the electronic conductivity and stability of the catalyst. As a result, NF/CoN_x@NC exhibits excellent HER performance. On the one hand, it only needs an overpotential of 69 mV to deliver a current density of 20 mA cm^-2 in 1.0 mol/L KOH, far better than that of CoN_x (182 mV). On the other hand, the electronic conductivity and stability of the catalyst can be significantly enhanced after the introduction of NC. This work has done successful material design with the goal of enhancing the intrinsic activity, electronic conductivity, and stability, which has certain reference and guiding significance for the design of novel transition metal-based electrocatalysts.