Boosting CO2 Electroreduction on Bismuth Nanoplates with a Three-Dimensional Nitrogen-Doped Graphene Aerogel Matrix

Controllable Reconstruction of β-Bi2O3/Bi2O2CO3 Composite for Highly Efficient and Durable Electrochemical CO2 Conversion

The uncontrollable electrochemical reduction reconstruction, leading to the destruction of well-defined structure and subsequent low durability, is the main obstacle to the catalytic performance of Bi-based composites toward electrochemical CO2 reduction reaction (eCO2RR). Herein, we address this issue through construction of a novel β-Bi2O3/Bi2O2CO3 composite, which can resist the reduction reconstruction of Bi-based materials to metallic Bi during the eCO2RR process by modulating a more alkaline microenvironment that facilitates the formation of new Bi-O bonds. The synergistic interactions and directional electron transfer between the β-Bi2O3 and Bi2O2CO3 components, together with the stable composite structure, result in its superior activity and selectivity for formate production with high faradaic efficiencies (FEs) over 94% from -0.7 to -1.1 V, and remarkable durability with maintenance of 80% FE after continuous electrocatalysis of 720 h. This work sheds new light on designing advanced high-performance nanomaterials toward eCO2RR and other practical applications.

Recent Advances in Electrocatalytic C-N Coupling for Urea Synthesis

Urea, one of the most widely used nitrogen-containing fertilizers globally, is essential for sustainable agriculture. Improving its production is crucial for meeting the increasing demand for fertilizers. Electrocatalytic co-reduction of CO₂ and nitrogenous compounds (NO₂-/NO₃-) has emerged as a promising strategy for green and energy-efficient urea synthesis. However, challenges such as slow reaction kinetics and complex multi-step electron transfers have hindered the development of efficient urea synthesis methods. This review explores recent advances in the electrocatalytic C-N coupling process, focusing on bimetallic catalysts, metal oxide/hydroxide catalysts, and carbon-based catalysts. The review also discusses the future prospects of designing effective catalysts for electrocatalytic C-N coupling to improve urea synthesis.

Graphene quantum dot-mediated anchoring of highly dispersed bismuth nanoparticles on porous graphene for enhanced electrocatalytic CO2 reduction to formate

The electrocatalytic reduction of CO2 to produce formic acid is gaining prominence as a critical technology in the pursuit of carbon neutrality. Nonetheless, it remains challenging to attain both substantial formic acid production and high stability across a wide voltage range, particularly when utilizing bismuth-based catalysts. Herein, we present a novel graphene quantum dot-mediated synthetic strategy to achieve the uniform deposition of highly dispersed bismuth nanoparticles on porous graphene. This innovative design achieves an elevated faradaic efficiency for formate of 87.0% at -1.11 V vs. RHE with high current density and long-term stability. When employing a flow cell, a maximum FEformate of 80.0% was attained with a total current density of 156.5 mA cm-2. The exceptional catalytic properties can be primarily attributed to the use of porous graphene as the support and the auxiliary contribution of graphene quantum dots, which enhance the dispersion of bismuth nanoparticles. This improved dispersion, in turn, has a significantly positive impact on CO2 activation and the generation of *HCOO intermediates to facilitate the formation of formate. This work presents a straightforward technique to create uniform metal nanoparticles on carbon materials for advancing various electrolytic applications.

Electrothermal Transformations within Graphene-Based Aerogels through High-Temperature Flash Joule Heating

Flash Joule heating of highly porous graphene oxide (GO) aerogel monoliths to ultrahigh temperatures is exploited as a low carbon footprint technology to engineer functional aerogel materials. Aerogel Joule heating to up to 3000 K is demonstrated for the first time, with fast heating kinetics (∼300 K·min-1), enabling rapid and energy-efficient flash heating treatments. The wide applicability of ultrahigh-temperature flash Joule heating is exploited in a range of material fabrication challenges. Ultrahigh-temperature Joule heating is used for rapid graphitic annealing of hydrothermal GO aerogels at fast time scales (30-300 s) and substantially reduced energy costs. Flash aerogel heating to ultrahigh temperatures is exploited for the in situ synthesis of ultrafine nanoparticles (Pt, Cu, and MoO2) embedded within the hybrid aerogel structure. The shockwave heating approach enables high through-volume uniformity of the formed nanoparticles, while nanoparticle size can be readily tuned through controlling Joule-heating durations between 1 and 10 s. As such, the ultrahigh-temperature Joule-heating approach introduced here has important implications for a wide variety of applications for graphene-based aerogels, including 3D thermoelectric materials, extreme temperature sensors, and aerogel catalysts in flow (electro)chemistry.

Zn Single Atoms/Clusters/Nanoparticles Embedded in the Hybrid Carbon Aerogels for High-Performance ORR Electrocatalysis

Carbon-supported zinc single-atom catalysts have received considerable attention in the electrocatalytic oxygen reduction reaction (ORR) owing to the strong reduction capacity of zinc atoms and the abundant reserves of zinc elements. The common preparation method has been limited to the high-temperature pyrolysis of nitrogen-rich organic molecules and zinc ions, which makes it difficult to further improve the ORR performance. Herein, we first prepared ZnO/PNT/rGO aerogels as precursors via a simple hydrothermal method combined with freeze-drying, in which reduced graphene oxides (rGO) and polypyrrole nanotubes (PNT) together assembled into three-dimensional frames and numerous ZnO nanoparticles were anchored in the three-dimensional skeletons. Then, ZnO/PNT/rGO aerogels were calcined at 800 °C in the argon atmosphere, in which PNT/rGO were derived carbon aerogels, ZnO nanoparticles were reduced to Zn0 by carbon, and generating zinc single atoms were captured by the surrounding nitrogen atoms or aggregated into Zn clusters/nanoparticles in the carbon substrates. The obtained products were Zn single atoms/clusters/nanoparticles embedded into PNT/rGO-derived carbon aerogels, named Zn/NC catalysts. Zn/NC catalysts display a much higher half-wave potential and a larger limiting current density than pure rGO aerogels, NC, and Zn/C catalysts, indicating the synergy of excellent electronic transportation, high mass efficiency from outstanding porosity, and several active centers. Tailoring the quantity of zinc acetate can provide the optimal ORR performance with the Eonset of 0.96 V, the E1/2 of 0.845 V, and remarkable durability. This work exploits a novel strategy of carbon thermal reduction to construct high-performance Zn-based low-dimensional ORR catalysts.