Co–N Active Sites between Co Nanoparticles and N-Doped Carbon toward Remarkably Enhanced Electrocatalytic Oxygen Evolution and Hydrogen Evolution Reactions

Abstract

The rational design and synthesis of a non-noble-metal electrocatalyst for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with good conductivity, high efficiency, and excellent stability are major challenges in the field of renewable energy. Therefore, we developed a simple and effective method to grow ZIF-67 in situ on graphitic carbon nitride (GCN) and then annealed it to generate nitrogen-doped carbon (NC) loaded with Co@C nanoparticles (Co@C/NC). Benefiting from this in situ growth method, after annealing, a large number of N atoms on the surface of NC nanosheets anchor more metal Co to form more catalytic Co–N active sites. At the same time, the Co@C/NC composites use NC nanosheets as the matrix, which can improve the electrochemical double-layer capacitance and conductivity of the composites. As demonstrated in electrochemical measurements, the OER and HER overpotentials of Co@C/NC composites at a current density of 10 mA cm–2 were only 300 and 175.4 mV in 1.0 M KOH, respectively. The preparation method is suitable for synthesizing various metal and carbon composite electrocatalysts. It provides ideas for designing and manufacturing high-performance non-noble-metal dual-function OER/HER catalysts.

Oxygen Defect-Enriched Hierarchical NiCo2O4 Hollow Rectangular Nanobars with Enhanced Bifunctional Oxygen Electrocatalysis for Efficient Rechargeable Zinc–Air Batteries

“…Rechargeable zinc–air batteries (RZABs) have been perceived as potential candidates for application in next-generation electric vehicles and other portable electronic equipment due to their distinguishing features of higher energy density, lower cost, better safety, and environmental friendliness compared to current lithium-ion batteries. − The performance of RZABs maintains a close association with the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) during charge and discharge processes, respectively. However, the intrinsically sluggish nature of both ORR and OER demands utilization of appropriate catalysts to boost the reaction kinetics, realizing an efficient and rapid mutual conversion between electric energy and chemical energy. , Therefore, developing efficient bifunctional oxygen electrocatalysts is the most important part for practical application of RZABs. − Thus far, noble metals such as Pt and/or Pt-based alloy electrocatalysts are presently regarded as the most efficient materials for ORR and OER, respectively. Still, their high cost and scarce reserve greatly impeded their widespread utilization .…”

Design of Hierarchical Oxide‐Carbon Nanostructures for Trifunctional Electrocatalytic Applications

“…[35] Moreover, metal nanoparticles promote the Volmer step by optimizing surface states of M-N x centers which reduces the energy barriers for water molecule dissociation. [87,88] CPNP@NC_NCO consists of NiCo nanoparticles in 1D and 2D carbon matrix and M-N x centers. Therefore, the CPNP@NC_NCO shows the best HER activity with minimal onset potential, overpotential, and highest current density.…”

“…The energy barrier for the initial water dissociation step in transition metal-N doped carbon nanostructure (M-N x centers) can be reduced by incorporating metal nanoparticles in the M-N-C framework. [41,54] From the volcano plot (apex of the volcano signifies the balance of *H adsorption and H 2 desorption) for various metal catalysts, Co and Ni lie after the precious metal Pt/Pd. [55] Therefore, Co/Ni-N x along with CoNi nanoparticles can be suitable for HER.…”

Hollow Co/N-C@NiCo2O4 Spheres as Highly Efficient Bifunctional Oxygen Electrocatalysts for Rechargeable Zinc–Air Batteries

“…Thus, improving the reaction kinetics in ORR/OER is a crucial step for promoting the comprehensive performance of zinc–air batteries. − Pt/Ru-based materials are widely used in ORR and OER, − but their high cost and scarcity greatly limit their commercial application. Aiming at this dilemma, cost-effective and high-performance nonprecious metal-based electrocatalysts are critical for the commercialized application of zinc–air batteries. − …”