In Situ Structure Refactoring of Bismuth Nanoflowers for Highly Selective Electrochemical Reduction of CO2 to Formate

The electrocatalytic CO₂ reduction reaction (CO₂RR) has been considered a promising route toward carbon neutrality and renewable energy conversion. At present, most bismuth (Bi) based electrocatalysts are adopted to reduce CO₂ to formate (HCOOH). However, the mechanism of different Bi nanostructures on the electrocatalytic performance requires more detailed exposition. Herein, a combined chemical replacement and electrochemical reduction process is reported to realize in situ morphology reconstruction from Bi@Bi₂O₃ nanodendrites (Bi@Bi₂O₃-NDs) to Bi nanoflowers (Bi-NFs). The Bi@Bi₂O₃-NDs are proven to undergo a two-step transformation process to form Bi-NFs, aided by Bi₂O₂CO₃ as the intermediate in KHCO₃ solution. Extensive surface reconstruction of Bi@Bi₂O₃-NDs renders the realization of tailored Bi-NFs electrocatalyst that maximize the number of exposed active sites and active component (Bi⁰), which is conducive to the adsorption and activation of CO₂ and accelerated electron transfer process. The as-prepared Bi-NFs exhibit a Faradaic efficiency (FE_formate) of 92.3% at −0.9 V versus RHE and a high partial current density of 28.5 mA cm⁻² at −1.05 V versus RHE for the electroreduction of CO₂ to HCOOH. Moreover, the reaction mechanism is comprehensively investigated by in situ Raman analysis, which confirms that *OCHO is a key intermediate for the formation of HCOOH.     

Anti-CO Poisoning FePtRh Nanoflowers with Rh-Rich Core and Fe-Rich Shell Boost Methanol Oxidation Electrocatalysis

Introducing oxophilic metals into Pt-based alloy catalysts can effectively alleviate the poisoning by CO intermediates (CO*) during methanol oxidation reactions (MOR). However, excessive oxophilic metals on the surface of catalysts tend to form thermodynamically stable carbonyl compound-like structures, occupying electrocatalytically active sites, which is not conducive to the enhancement of catalytic activity. Herein, a kind of surface segregated FePtRh nanoflowers for effectively eliminating the CO* poisoning during MOR electrocatalysis is presented. The FePtRh nanoflowers are constituted by the Rh-rich core and Fe-rich shell. The optimized Fe₂₁Pt₆₆Rh₁₃/C shows a high mass activity of 3.90 A mg_Pt⁻¹ and a specific activity of 4.85 mA cm⁻². It is confirmed that the electron transfer from Pt to Rh or Fe atoms is beneficial for the higher anti-CO poisoning ability, which mainly originate from the alloying of Rh atoms and surface-segregated structures. Density functional theory calculations reveal the decreased electrons adsorbed by CO* on both Pt–Pt bridge sites and top sites weakens the strong adsorption energy between Pt atoms and CO* intermediates. The optimal nanoflowers also show excellent performance toward ethanol oxidation reaction (EOR) with a high mass activity of 2.76 A mg_Pt⁻¹ and the enhanced anti-CO poisoning ability, as well as the improved stability.     

Controlled development of higher-dimensional nanostructured copper oxide thin films as binder free electrocatalysts for oxygen evolution reaction

The development of cost-effective and highly efficient electrocatalysts for oxygen evolution reaction (OER) is a grave challenge in water splitting catalysis for the clean and viable production of molecular hydrogen (H₂). Herein, we report the fabrication of higher-dimensional thin film CuO nanostructures with controlled morphologies i.e., nanosheets, nanocubes, nanoflowers, and nanoleaves and their relative performance for water oxidation catalysis. Among these nanostructures, CuO nanoflowers exhibit high catalytic activity with an onset potential of 1.48 V and a Tafel slope of 84 mVdec⁻¹ in 1 M KOH solution. Moreover, an overpotential of 270 mV and 400 mV is needed to attain a current density of 10 mAcm⁻² and 100 mAcm⁻² respectively with high Faradaic efficiency. More promisingly, the catalytic performance was found highly dependent upon the nanoscale features and subsequently the improved electrochemically active surface area (ECSA). Such morphology dependent OER performance and binder-free nature of catalyst may provide the high-speed track for electrons transport owing to the inherent catalyst-substrate electronic interconnection and thus making it more promising and high-performance electrocatalyst for OER.     

Unique hierarchical mesoporous LaCrO3 perovskite oxides for highly efficient electrochemical energy storage applications

Following sol-gel route, hierarchical mesoporous nanostructures of lanthanum chromates (LaCrO₃) perovskite oxides are successfully synthesized for supercapacitor applications. The structural behaviors of nano perovskite oxides are investigated using X-rays diffraction, low and high resolution scanning and transmission electron microscopes, photoelectron X-ray spectroscopy, and Brunauer-Emmett-Teller (BET). The as-prepared LaCrO₃ powders is mingled with activated carbon and subsequently glazed on a flexible carbon cloth current collector (LCO@CC). The electrochemical capabilities of LCO@CC based electrode, such as: cyclic voltammetry, galvanostatic charge:discharge and electrochemical impedance spectroscopy are investigated in neutral M LiCl aqueous solutions. Moreover, the fabricated LCO@CC electrode achieves maximum capacitance of 1268 F/g at 2 A/g and retains excellent cyclic ability of 91.5% after 5000 charge:discharge cycles. The efficient electrochemical performances of carbon cloth decorated LaCrO₃ electrode are credited to dynamic charge storage mechanism by fast redox reaction of electrolyte-electrode interactions with extremely low charge transfer resistance.     

3D MoS2/graphene nanoflowers as anode for advanced lithium-ion batteries

Vertical MoS₂ nanosheets were controllably patterned onto graphene as nanoflowers through a two-step hydrothermal method. The interconnected network and intimate contact between MoS₂ nanosheets and graphene by vertical channels enabled a high mechanical integrity of electrode and cycling stability. In particular, MoS₂/graphene nanoflowers anode delivered an ultrahigh specific capacity of 901.8 mA·h/g after 700 stable cycles at 1000 mA/g and a corresponding capacity retention as 98.9% from the second cycle onwards.