Controlled Synthesis and Structure Engineering of Transition Metal-based Nanomaterials for Oxygen and Hydrogen Electrocatalysis in Zinc-Air Battery and Water-Splitting Devices

Stabilization of LiCoO2 Cathodes in High Voltage Lithium Metal Batteries Through 2-(Trifluoromethyl)Benzamide (2-TFMBA) Electrolyte Additives

Increasing the charging cutoff voltage of LiCoO2 to 4.6 V is significant for enhancing battery density. However, the practical application of Li‖LiCoO2 batteries with a 4.6 V cutoff voltage faces significant impediments due to the detrimental changes under high voltage. This study presents a novel bifunctional electrolyte additive, 2-(trifluoromethyl)benzamide (2-TFMBA), which is employed to establish a stable and dense cathode-electrolyte interface (CEI). Characterization results reveal that an optimized CEI is achieved through the synergistic effects of the amide groups and trifluoromethyl groups within 2-TFMBA. The resulting CEI not only enhances the structural stability of LiCoO2 but also serves as a high-speed lithium-ion conduction channel, which expedites the insertion and extraction of lithium ions. The Li‖LiCoO2 batteries with 0.5 wt% 2-TFMBA achieves an 84.7% capacity retention rate after enduring 300 cycles at a current rate of 1 C, under a cut-off voltage of 4.6 V. This study provides valuable strategic insights into the stabilization of cathode materials in high-voltage batteries.

Self-catalyzed Co, N-doped carbon nanotubes-grafted hollow carbon polyhedrons as efficient trifunctional electrocatalysts for zinc-air batteries and self-powered overall water splitting

It is still essential and challenging to explore inexpensive and versatile electrocatalysts for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER), for the development of rechargeable zinc-air batteries (ZABs) and overall water splitting. Herein, a rambutan-like trifunctional electrocatalyst is fabricated by re-growth of secondary zeolitic imidazole frameworks (ZIFs) on ZIF-8-derived ZnO and the following carbonization treatment. Co nanoparticles (NPs) are encapsulated into N-doped carbon nanotubes (NCNT) grafted N-enriched hollow carbon (NHC) polyhedrons to form the Co-NCNT@NHC catalyst. The strong synergy between the N-doped carbon matrix and Co NPs endows Co-NCNT@NHC with trifunctional catalytic activity. The Co-NCNT@NHC displays a half-wave potential of 0.88 V versus RHE for ORR in alkaline electrolyte, an overpotential of 300 mV at 20 mA cm^-2 for OER, and an overpotential of 180 mV at 10 mA cm^-2 for HER. Impressively, a water electrolyzer is successfully powered by two rechargeable ZABs in series, with Co-NCNT@NHC as the 'all-in-one' electrocatalyst. These findings are inspiring for the rational fabrication of high-performance and multifunctional electrocatalysts intended for the practical application of integrated energy-related systems.

In Situ Interfacial Passivation in Aqueous Electrolyte for Mg-Air Batteries with High Anode Utilization and Specific Capacity

Mg-air batteries are a promising new generation of batteries because they can operate in neutral electrolytes that are safe and nontoxic. However, the high corrosion and low utilization of Mg anodes in Mg-air batteries result in low specific capacity and severe self-discharge. In this study, an Mg(OTf)₂ -based aqueous electrolyte is developed, which addresses these issues by reducing the contact of the Mg anode with water molecules from the hydrophobic -CF₃ groups and forming an MgF₂ protective layer. The assembled Mg-air batteries exhibit specific capacities of up to 1920 mAh g^-1 _Mg (87.32 % utilization based on the Mg anode). In addition, the resting time of the corresponding Mg-air batteries was 123 times longer than that of Mg-air batteries with pure NaCl electrolytes under the same conditions.

FeNiP nanoparticle/N,P dual-doped carbon composite as a trifunctional catalyst towards high-performance zinc-air batteries and overall water electrolysis

A composite catalyst with a novel construction of bimetallic phosphide FeNiP nanoparticles embedded in an N,P double-doped carbon matrix was prepared. It was demonstrated to be a trifunctional catalyst that can efficiently catalyze the oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). It was found that the introduction of oleylamine during the preparation can adjust the catalytic sites and finally lead to ideal catalytic performances. The obtained catalyst exhibited efficient ORR catalytic performance that surpassed the commercial Pt/C catalyst, with the OER performance comparable to that of RuO₂ as well as excellent HER performance. The ORR half-wave potential is 0.879 V (vs. RHE) in 0.1 M KOH solution, while the OER overpotential at a current density of 10 mA cm^-2 is only 280 mV in 1 M KOH solution. The potential gap between the ORR and OER was only 0.700 V in 0.1 M KOH solution. This trifunctional catalyst was further evaluated in energy devices including zinc-air batteries and water electrolysis. The liquid zinc-air battery assembly achieved a power density of 169 mW cm^-2 and stably undergoes charge-discharge cycles for 210 hours. The solid-state zinc-air battery achieved a power density of 70 mW cm^-2 and stably undergoes charge-discharge cycles for 40 hours. These performances surpassed the batteries assembled with a Pt/C-RuO₂ mixed catalyst. This work established a foundation of composite catalysts coupled with bimetallic phosphide and hybrid carbon substrates, which will promote the development of high-performance multifunctional catalysts and their application in energy devices.

Graphene-induced growth of Co3O4 nanoplates with modulable oxygen vacancies for improved OER properties

Graphene-induced growth of Co(OH)2 nanoplates from Co3O4 nanospheres was reported, showing an ultralow overpotential of 240 mV at 10 mA cm−2 and a Tafel slope of 107.8 mV dec−1.