RESUMEN
Electrochemical reduction reactions, as cathodic processes in many energy-related devices, significantly impact the overall efficiency determined mainly by the performance of electrocatalysts. Metal-organic frameworks (MOFs) derived carbon-supported metal materials have become one of star electrocatalysts due to their tunable structure and composition through ligand design and metal screening. However, for different electroreduction reactions, the required active metal species vary in phase component, electronic state, and catalytic center configuration, hence requiring effective customization. From this perspective, this review comprehensively analyzes the structural design principles, metal loading strategies, practical electroreduction performance, and complex catalytic mechanisms, thereby providing insights and guidance for the future rational design of such electroreduction catalysts.
RESUMEN
Deep-sea equipment usually operates under dwell-fatigue condition, which means the equipped energy storage devices must survive under the changing pressure. Special mechanical designs should be considered to maintain the electrochemical performance of electrodes under this extreme condition. In this work, an effective assembly strategy is proposed to accommodate the dwell-fatigue loading using Ag decorated reduced graphene oxide (rGO) foam (denoted as AGF) as a superelastic and robust Zn host. The wet-press assembly process enables the formation of highly porous and robust framework. The strong synergetic effect between rGO and Ag further guarantees AGF's superelasticity and ultrahigh mechanical strength. Meanwhile, the homogeneously distributed Ag species on the rGO sheets act as zincophilic sites to effectively facilitate Zn plating. Furthermore, AGF offers enough space to address the expansion during the charge and discharge cycles. As expected, the symmetrical cell using this AGF@Zn host demonstrates a long lifespan over 400 h at a depth-of-discharge of 50%. It is worth mentioning that the superelastic AGF host realizes stable Zn plating/stripping under varying pressures.
RESUMEN
Direct electrosynthesis of hydrogen peroxide (H2O2) with high production rate and high selectivity through the two-electron oxygen reduction reaction (2e-ORR) offers a sustainable alternative to the energy-intensive anthraquinone technology but remains a challenge. Herein, a low-coordinated, 2D conductive Zn/Cu metal-organic framework supported on hollow nanocube structures (ZnCu-MOF (H)) is rationally designed and synthesized. The as-prepared ZnCu-MOF (H) catalyst exhibits substantially boosted electrocatalytic kinetics, enhanced H2O2 selectivity, and ultra-high Faradaic efficiency for 2e-ORR process in both alkaline and neutral conditions. Electrochemical measurements, operando/quasi in situ spectroscopy, and theoretical calculation demonstrate that the introduction of Cu atoms with low-coordinated structures induces the transformation of active sites, resulting in the beneficial electron transfer and the optimized energy barrier, thereby improving the electrocatalytic activity and selectivity.
RESUMEN
The controllable photocatalytic C-C coupling of methanol to produce ethylene glycol (EG) is a highly desirable but challenging objective for replacing the current energy-intensive thermocatalytic process. Here, we develop a metal-free porous boron nitride catalyst that demonstrates exceptional selectivity in the photocatalytic production of EG from methanol under mild conditions. Comprehensive experiments and calculations are conducted to thoroughly investigate the reaction mechanism, revealing that the OB3 unit in the porous BN plays a critical role in the preferential activation of C-H bond in methanol to form â CH2OH via a concerted proton-electron transfer mechanism. More prominent energy barriers are observed for the further dehydrogenation of the â CH2OH intermediate on the OB3 unit, inhibiting the formation of some other by-products during the catalytic process. Additionally, a small downhill energy barrier for the coupling of â CH2OH in the OB3 unit promotes the selective generation of EG. This study provides valuable insights into the underlying mechanisms and can serve as a guide for the design and optimization of photocatalysts for efficient and selective EG production under mild conditions.
RESUMEN
The artificial disturbance in the nitrogen cycle has necessitated an urgent need for nitric oxide (NO) removal. Electrochemical technologies for NO conversion have gained increasing attention in recent years. This comprehensive review presents the recent advancements in selective electrocatalytic conversion of NO to high value-added chemicals, with specific emphasis on catalyst design, electrolyte composition, mass diffusion, and adsorption energies of key intermediate species. Furthermore, the review explores the synergistic electrochemical co-electrolysis of NO with specific carbon source molecules, enabling the synthesis of a range of valuable chemicals with CâN bonds. It also provides in-depth insights into the intricate reaction pathways and underlying mechanisms, offering valuable perspectives on the challenges and prospects of selective NO electrolysis. By advancing comprehension and fostering awareness of nitrogen cycle balance, this review contributes to the development of efficient and sustainable electrocatalytic systems for the selective synthesis of valuable chemicals from NO.
RESUMEN
Photocatalytic O2 reduction is an intriguing approach to producing H2O2, but its efficiency is often hindered by the limited solubility and mass transfer of O2 in the aqueous phase. Here, we design and fabricate a two-layered (2L) Janus fiber membrane photocatalyst with asymmetric hydrophobicity for efficient photocatalytic H2O2 production. The top layer of the membrane consists of superhydrophobic polytetrafluoroethylene (PTFE) fibers with a dispersed modified carbon nitride (mCN) photocatalyst. Amphiphilic Nafion (Naf) ionomer is sprayed onto this layer to modulate the microenvironment and achieve moderate hydrophobicity. In contrast, the bottom layer consists of bare PTFE fibers with high hydrophobicity. The elaborate structural configuration and asymmetric hydrophobicity feature of the optimized membrane photocatalyst (designated as 2L-mCN/F-Naf; F, PTFE) allow most mCN to be exposed with gas-liquid-solid triple-phase interfaces and enable rapid mass transfer of gaseous O2 within the hierarchical membrane, thus increasing the local O2 concentration near the mCN photocatalyst. As a result, the optimized 2L-mCN/F-Naf membrane photocatalyst shows remarkable photocatalytic H2O2 production activity, achieving a rate of 5.38 mmol g-1 h-1 under visible light irradiation.
RESUMEN
Exploring unique single-atom sites capable of efficiently reducing O2 to H2 O2 while being inert to H2 O2 decomposition under light conditions is significant for H2 O2 photosynthesis, but it remains challenging. Herein, we report the facile design and fabrication of polymeric carbon nitride (CN) decorated with single-Zn sites that have tailorable local coordination environments, which is enabled by utilizing different Zn salt anions. Specifically, the O atom from acetate (OAc) anion participates in the coordination of single-Zn sites on CN, forming asymmetric Zn-N3 O moiety on CN (denoted as CN/Zn-OAc), in contrast to the obtained Zn-N4 sites when sulfate (SO4 ) is adopted (CN/Zn-SO4 ). Both experimental and theoretical investigations demonstrate that the Zn-N3 O moiety exhibits higher intrinsic activity for O2 reduction to H2 O2 than the Zn-N4 moiety. This is attributed to the asymmetric N/O coordination, which promotes the adsorption of O2 and the formation of the key intermediate *OOH on Zn sites due to their modulated electronic structure. Moreover, it is inactive for H2 O2 decomposition under both dark and light conditions. As a result, the optimized CN/Zn-OAc catalyst exhibits significantly improved photocatalytic H2 O2 production activity under visible light irradiation.