Multi-dimensional hierarchical CoS2@MXene as trifunctional electrocatalysts for zinc-air batteries and overall water splitting

Abstract

The demanding all-in-one electrocatalyst system for oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in zinc-air batteries or water splitting requires elaborate material manufacturing, which is usually complicated and time-consuming. Efficient interface engineering between MXene and highly active electrocatalytic species (CoS 2 ) is, herein, achieved by an in situ hydrothermal growth and facile sulfurization process. The CoS 2 @MXene electrocatalyst is composed by one-dimensional CoS 2 nanowires and two-dimensional MXene nanosheets, which lead to a hierarchical structure (large specific surface area and abundant active sites), a spatial electron redistribution (high intrinsic activity), and high anchoring strength (superior performance stability). Therefore, the electrocatalyst achieves enhanced catalytic activity and longtime stability for ORR (a half-wave potential of 0.80 V), OER (an overpotential of 270 mV at 10 mA cm −2 , i.e., η 10 = 270 mV) and HER (η 10 = 175 mV). Furthermore, the asymmetry water splitting system based on the CoS 2 @MXene composites delivers a low overall voltage of 1.63 V at 10 mA cm −2 . The solidstate zinc-air batteries using CoS 2 @MXene as the air cathode display a small charge-discharge voltage gap (0.53 V at 1 mA cm −2 ) and superior stability (60 circles and 20-h continuous test). The energy interconversion between the chemical energy and electricity can be achieved by a self-powered system via integrating the water splitting system and quasisolid-state zinc-air batteries. Supported by in situ Raman analyses, the formation of cobalt oxyhydroxide species provides the active sites for water oxidation. This study paves a promising avenue for the design and application of multifunctional nanocatalysts.

Recent Advances on MXene‐Based Electrocatalysts toward Oxygen Reduction Reaction: A Focused Review

“…In a comparative ORR-based analysis of the catalysts, the NiFeMn trimetallic nitride/N-Ti 3 C 2 catalyst exhibited excellent ORR activity with onset and half-wave potentials of 0.95 and 0.84 V, respectively (Figure 12m-o). Han et al [136] synthesized CoS 2 @Ti 3 C 2 T x through a hydrothermal and subsequent sulfurization synthesis process. The sulfurization of the precursor Co(OH) 2 @MXene, is performed with a sulfur power at 450 °C for 2 h. Due to lower sulfurization process, the XRD patterns did not show any decomposition of Ti 3 C 2 T x .…”

“…Han et al. [ 136 ] synthesized CoS 2 @Ti 3 C 2 T x through a hydrothermal and subsequent sulfurization synthesis process. The sulfurization of the precursor Co(OH) 2 @MXene, is performed with a sulfur power at 450 °C for 2 h. Due to lower sulfurization process, the XRD patterns did not show any decomposition of Ti 3 C 2 T x .…”

Anchoring stable FeS2 nanoparticles on MXene nanosheets via interface engineering for efficient water splitting

“…[35][36][37][38] The intrinsic properties of MXene, including unique morphologies, a super hydrophilic surface, metallic conductivity and excellent mechanical properties, make it attract widespread attention in various energy fields. [39][40][41][42][43][44] Especially, the tunable terminated functional groups endow MXene with the characteristic of having controllable properties, which makes it be possible to construct novel hybrid systems with greater flexibility. 45,46 Analogous to most two-dimensional materials, MXene nanosheets tend to self-aggregate owing to the van der Waals force and hydrogen-bond interactions, which causes performance degradation owing to the decrease in the surface area.…”

Simultaneous heterostructure engineering and Mn doping modulation of Ni2P nanosheet arrays for enhanced electrocatalytic water splitting

“…With the frequency of environmental issues and extreme climate changes caused by the mass depletion of conventional fossil resources, there is an urgent requirement for clean and renewable energy, such as bioenergy, solar power, and wind energy, to supersede conventional nonrenewable fossil resources [1][2][3]. However, the weather dependence of wind energy and solar power impedes large-scale applications [4].…”