Electrochemically synthesized SnO2 with tunable oxygen vacancies for efficient electrocatalytic nitrogen fixation.

Electrochemical nitrogen reduction reaction (NRR) driven by a renewable energy source offers a sustainable and environmentally benign route to produce ammonia (NH3), but it is highly dependent on efficient and specific catalysts to reduce the high reaction barrier and improve the selectivity. Defect engineering is extensively used to regulate the surface properties of materials to improve their catalytic performance. Herein we synthesized SnO2 with different oxygen vacancy concentrations by a controllable electrochemical method for electrocatalytic nitrogen (N2) fixation. The prepared SnO2 was used as an electrocatalyst and exhibited excellent NRR performance with an optimal NH3 yield rate of 25.27 µg h-1 mgcat.-1 and faradaic efficiency of 11.48% at -0.6 V (vs. the reversible hydrogen electrode) in 0.1 M Na2SO4. Oxygen vacancies provide more active sites and greater electron transfer ability on the catalyst surface to facilitate N2 adsorption and activation. The electrocatalytic NRR performance of SnO2 was enhanced with the increase in oxygen vacancy concentration. The density functional theory calculations indicate that the oxygen vacancies in SnO2 promote the electrocatalytic NRR performance by increasing the number of valence electrons of Sn and decreasing the energy barrier of the potential-determining step, thus promoting the activation of the N-N bond to further achieve efficient N2 fixation.

Tin dioxide-based nanomaterials as anodes for lithium-ion batteries.

The development of new electrode materials for lithium-ion batteries (LIBs) has attracted significant attention because commercial anode materials in LIBs, like graphite, may not be able to meet the increasing energy demand of new electronic devices. Tin dioxide (SnO2) is considered as a promising alternative to graphite due to its high specific capacity. However, the large volume changes of SnO2 during the lithiation/delithiation process lead to capacity fading and poor cycling performance. In this review, we have summarized the synthesis of SnO2-based nanomaterials with various structures and chemical compositions, and their electrochemical performance as LIB anodes. This review addresses pure SnO2 nanomaterials, the composites of SnO2 and carbonaceous materials, the composites of SnO2 and transition metal oxides, and other hybrid SnO2-based materials. By providing a discussion on the synthesis methods and electrochemistry of some representative SnO2-based nanomaterials, we aim to demonstrate that electrochemical properties can be significantly improved by modifying chemical composition and morphology. By analyzing and summarizing the recent progress in SnO2 anode materials, we hope to show that there is still a long way to go for SnO2 to become a commercial LIB electrode and more research has to be focused on how to enhance the cycling stability.