NiFe
layered double hydroxide (NiFe LDH) grown in the presence
of MoS2 (rich in 1T phase) shows exceptional performance
metrics for alkaline oxygen evolution reaction (OER) in this class
of composites. The as-prepared NiFe LDH/MoS2 composite
(abbreviated as MNF) exhibits a low overpotential (η10) of 190 mV; a low Tafel slope of 31 mV dec–1;
and more importantly, a high stability in its performance manifested
by the delivery of current output for 45 h. It is important to note
that this could be achieved with an exceedingly low loading of 0.14
mg cm–2. The mass activity of this composite (97
A g–1) is about 14 times greater than that of the
conventional RuO2 (7 A g–1) at η
= 200 mV. When normalized with respect to the total metal content,
a mass activity of 1000 A g–1 (η = 300 mV)
was achieved. Impedance analysis further reveals that the significant
reduction in charge-transfer resistance and hence high current density
(5 times greater as compared to NiFe LDH at η = 300 mV) observed
for MNF is associated with interfacial adsorption kinetics of intermediates
(R
1). Significant enhancement in the intrinsic
activity of MNF over LDH has been observed through normalization of
current with the electrochemically active surface area. Computational
studies suggest that the Ni centers in the composite act as the active
sites for OER, which is well-corroborated with the observed postreaction
appearance of Ni3+ species.
Mass transport and
charge transfer at an interface play a crucial
role in governing the electrochemical performance of a material. Wider
meso-/macropores are expected to enhance the reaction kinetics by
facilitating the ion transport to and fro from an active interface,
thereby continuously regenerating it at accelerated rates. Herein,
we report a generic, simple, and ultrafast synthetic method to obtain
highly graphitized porous carbon containing well-dispersed Co3O4 nanoparticles (∼1 wt % Co) using cobalt
acetate and piperidine precursors. The obtained catalyst (Co3O4@CS) exhibits onset potential and oxygen evolution kinetics
similar to that of the state-of-the-art catalyst, RuO2.
For oxygen evolution reaction (OER), the synthesized material exhibits
excellent cycling performance over 2000 cycles. Such a performance
metric can be attributed to the uniform dispersion of active sites
(Co3O4) over a low-density, highly interconnected
conducting carbon matrix leading to facile mass transport and charge
transfer, respectively.
Viologen based covalent organic polymer (COP) interfaced with graphene at the nanoscale showed pseudocapacitive energy storage associated with redox‐active moieties. The positively charged viologen moieties endow charge storage as well as easy wetting of the electrode. The non‐conducting COP grown over conducting graphene enhances its performance by extensive interface formation. All the redox states of viologen moieties can be reversibly attained without significant polarization when it is interfaced with graphene. However, the COP (devoid of graphene) shows irreversible/pseudo‐reversible behavior due to lack of electron conducting pathways. The intimate and dense conducting pathways in graphene‐COP composites facilitates the charge transfer across interface leading to effective and reversible participation of redox moieties across the entire range over 1000 cycles. Also, we show that the strategy being universal in nature and aid in electron transfer in dense 3D networks which lacks traditional π‐π stacking of 2D crystalline networks (COF).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.