Anodic SnO2 porous nanostructures with rich grain boundaries for efficient CO2 electroreduction to formate

Grain boundary/doping/architecture engineering in hierarchical N-doped CuO microflowers derived from Cu-based metal-organic framework architectures for highly efficient nonenzymatic glucose detection

Glucose detection is essential in clinical medicine, and the reasonable design of metal oxide electrocatalysts plays a crucial role in developing efficient nonenzymatic glucose (NEG) sensors. Herein, grain boundary/doping/architecture engineering is used to tailor the structures of CuO nanomaterials and tune their surface/electron-transfer properties toward enhanced electrocatalytic oxidation of glucose. Hierarchical N-doped CuO microflowers (N-CuO-MF) are synthesized using a facile hydrothermal method, followed by calcination. N-CuO-MF consist of ultrathin nanoflakes (ca. 20 nm), endowing them with a large specific surface area. Moreover, the nanoflakes are composed of ultrasmall nanoparticles, resulting in abundant grain boundaries. Notably, N-CuO-MF are derived from a precursor of Cu-based metal-organic framework (Cu-MOF) architectures, which is fabricated through a bottom-up route using glycerol as the capping agent/solvent and 1-hexadecyl-3-methylimidazolium bromide ([C16mim]Br) as the template/N source. Glycerol competitively coordinates with Cu2+, leading to the formation of 2D subunits. Moreover, [C16mim]+ cations attach to the subunit surfaces via electrostatic interaction, thus achieving Cu-MOF with a 3D hierarchical structure. As expected, the synergistic effect of rich grain boundaries, N doping, ultrathin nanoflakes, and hierarchical architecture enhances the adsorption of glucose on the electrode surfaces, accelerates electron transfer, and exposes more active sites for glucose oxidation. Accordingly, N-CuO-MF exhibit wide linear ranges, high sensitivity, fast response time, low detection limit, excellent selectivity, and good stability. Owing to their highly efficient electrocatalytic properties, N-CuO-MF could be explored as potential electrocatalysts in NEG sensors for rapid diagnostic tests and health monitoring.

Rare-earth Element-based Electrocatalysts Designed for CO2 Electro-reduction

Electrochemical CO2 reduction presents a promising approach for synthesizing fuels and chemical feedstocks using renewable energy sources. Although significant advancements have been made in the design of catalysts for CO2 reduction reaction (CO2RR) in recent years, the linear scaling relationship of key intermediates, selectivity, stability, and economical efficiency are still required to be improved. Rare earth (RE) elements, recognized as pivotal components in various industrial applications, have been widely used in catalysis due to their unique properties such as redox characteristics, orbital structure, oxygen affinity, large ion radius, and electronic configuration. Furthermore, RE elements could effectively modulate the adsorption strength of intermediates and provide abundant metal active sites for CO2RR. Despite their potential, there is still a shortage of comprehensive and systematic analysis of RE elements employed in the design of electrocatalysts of CO2RR. Therefore, the current approaches for the design of RE element-based electrocatalysts and their applications in CO2RR are thoroughly summarized in this review. The review starts by outlining the characteristics of CO2RR and RE elements, followed by a summary of design strategies and synthetic methods for RE element-based electrocatalysts. Finally, an overview of current limitations in research and an outline of the prospects for future investigations are proposed.

Elevating the p-band centre of SnO2 nanosheets through W incorporation for promoting CO2 electroreduction

SnO₂ is one of the most promising catalysts for CO₂ electroreduction. However, the intrinsic low electrical conductivity and weak CO₂ adsorption and activation capability have rendered the reaction kinetically sluggish and inefficient. To surmount these hurdles, herein, W was incorporated into SnO₂ nanosheets to modulate the electronic structures. Compared with pristine SnO₂, the p-band centre of W-doped SnO₂ was elevated towards the Fermi level, accompanied by the reduction in the band gap and work function. As a result, both the CO₂ adsorption and the electron transfer process were promoted, thus lowering the activation energy barrier for CO₂ reduction. Benefitting from these, a maximum faradaic efficiency of 87.8% was achieved for HCOOH at -0.9 V vs. the RHE. Meanwhile, the current density and energy efficiency approached 20.92 mA cm^-2 and 60%, respectively. Such performances could sustain for 14 h without obvious fading and exceeded pristine SnO₂ and most reported Sn-based catalysts. Tafel slope and reaction order analyses further suggested that the reaction proceeded following a stepwise electron-proton transfer pathway with the formation of CO₂˙^- as the rate determining step. This work demonstrated the effectiveness of electronic structure tuning in promoting the catalytic performances of p-block metal oxides and contributed to the development of efficient catalysts for sustainable energy conversion and carbon neutrality.