EES catalysis最新文献

We utilize operando X-ray computed tomography, coupled with real-time electrochemical analysis, to reveal the underlying failure mechanisms of membrane electrode assemblies (MEAs) for electrochemical CO₂ reduction (eCO₂R). Through operando imaging, we can obtain unprecedented insights into the dynamic behavior of the MEA under different operating conditions, revealing critical changes in interface interactions, phase distribution, and structural integrity over time. Our findings identify phenomena giving rise to the transition from CO₂R to the hydrogen evolution reaction (HER), as evidenced by shifts in cathode potential and CO₂R selectivity. The formation of inhomogeneous precipitates at the gas diffusion electrode disrupts the CO₂ supply and reduces the active sites for eCO₂R, resulting in a shift toward H₂ production during low current density operation. Additionally, under high current density conditions, rapid water crossover up to the microporous layer/gas diffusion layer promotes the transition from CO₂R to HER, further shifting cell potential toward anodic direction. Oscillating voltage conditions reveal the dissolution and regrowth of precipitates, providing direct visualization of the competing selectivity of CO₂R and HER. This work offers new insight into the degradation mechanisms of MEAs, with implications for the design of more durable CO₂R systems.

A conjugated polymer photocatalyst containing dual-electron acceptor units, dibenzo[b,d]thiophene sulfone (DBS) and 2,1,3-benzothiadiazole (BT), known as PBT, has been synthesized for its strong electron-withdrawing abilities and structural flexibility. However, the inherent hydrophobicity of PBT leads to significant particle aggregation, hindering colloidal stability and electron transfer to protons. To overcome these limitations, fluorine and ethylene glycol (EG) groups are strategically incorporated into the BT unit to enhance molecular planarity and hydrophilicity, respectively. This molecular engineering effectively suppresses exciton and charge recombination, facilitating efficient charge separation and extraction. Comprehensive spectroscopic analyses—including time-resolved photoluminescence (Tr-PL) and transient absorption spectroscopy (TAS)—reveal that EG-functionalized polymers exhibit prolonged exciton lifetimes and strong photoinduced absorption at early timescales, indicating both suppressed non-radiative recombination and effective charge generation. Importantly, these modifications enable rapid charge separation and transfer with more efficient electron extraction to protons, mitigating charge accumulation within aggregated domains. Among the modified polymers, 4EG-PBTz-F, with di-fluoro substituents and tetra-ethylene glycol groups, achieves the highest hydrogen evolution rates of 15.476 mmol g⁻¹ and 3.095 mmol g⁻¹ h⁻¹ with a 3 wt% Pt co-catalyst. These results highlight the effectiveness of dual-electron acceptor design and interfacial control, offering a multi-faceted design strategy in photocatalytic hydrogen evolution systems.

Recent advances in photocatalytic systems for H₂O₂ production have led to improvements in both efficiency and selectivity; however, the practical application of current photocatalysts remains limited by low H₂O₂ production rates, poor long-term stability, and challenges in scalability. In this study, we present a novel photocatalyst based on the integration of gold nanostars (AuNSs) into poly(heptazine imide) (PHI) resulting in a system that is highly efficient for H₂O₂ production. The resulting AuNSs–PHI catalyst achieved a remarkable H₂O₂ generation rate of 286.95 mM g⁻¹ h⁻¹ under solar irradiation, utilising O₂ reduction coupled with isopropanol oxidation. This enhanced performance is primarily attributed to localized surface plasmon resonance (LSPR) effects from the embedded gold nanostars, which significantly boost light absorption and charge separation efficiency. The critical role of the optimized nanostructure was further validated through time-dependent density functional theory (TDDFT) calculations on a gold cluster (Au₂₀) adsorbed onto PHI, providing theoretical insight into the observed experimental H₂O₂ production enhancement. These findings demonstrate the potential of plasmon-enhanced photocatalysis as a viable pathway for sustainable and scalable H₂O₂ production.

CO₂ hydrogenation to methanol using plasma provides a sustainable alternative to conventional, fossil-based production methods. Although numerous experimental studies in relevant field have been reported, a comprehensive techno-economic assessment is still lacking. Additionally, the influence of electricity supply strategies on the plasma process remains unexplored. Therefore, in this study, evaluation has been performed on a plasma-assisted methanol production process with emphasis on the effects of multiple electricity supply strategies. A process model was developed based on the state-of-the-art performance of a catalytic DBD plasma reactor. Then, the minimum methanol selling price (MMSP) was calculated to evaluate the economic feasibility of variable and continuous operation of the plasma process and different electricity supply strategies. The results indicated that, in all scenarios investigated, the plasma process can not directly compete with conventional benchmark processes. Among the prospective power supply strategies projected for 2050, a significant reduction in MMSP was observed, with the lowest MMSP achieved when using surplus renewable energy. However, even with this approach, the MMSP was 7277 € per t, more than seven times higher than the benchmark price. Continuous operation of the plasma process at maximum capacity could improve its economic performance enabling a reduction of the MMSP to 3601 € per t.

Traditional studies in comprehensive multicomponent spaces driven by redundant chemical experiments may overlook important features. Herein, we introduce historical experimental data and a theoretical volcano map, coupled with thermodynamic stability, to provide insights by feature ranking based on a robust formic acid oxidation reaction (FOR) database. Results indicate that the PdCuNi alloy catalyst screened by density functional theory (DFT) calculations and machine learning (ML) is a promising candidate for FOR. Electron-deficient surface Ni atoms promote the reduction of the thermodynamic energy barrier of FOR. A PdCuNi medium entropy alloy aerogel (PdCuNi AA) was successfully synthesized through a simple one-pot NaBH₄-reduction synthesis strategy. The obtained catalyst exhibits a mass activity of 2.7 A mg⁻¹, surpassing those of PdCu, PdNi and commercial Pd/C by approximately 2.1-, 2.7- and 6.9-fold, respectively. Moreover, PdCuNi AA achieves an impressive power density of around 153 mW cm⁻² with 0.5 mg cm⁻² loading in the anode of direct formic acid fuel cells. Combining cutting-edge methods to drive innovative catalyst design will play a key role in advancing the development of fuel cells.

Developing economical and environmentally friendly carbonylation synthetic methods is an important and challenging goal. Exploring the application of non-precious metal catalysts in synthetic chemistry has proven to be an ideal choice due to their abundancy, low cost, and low toxicity. In recent years, as copper is one of the cheaper metals, copper catalysts have been widely used in the field of carbonylative transformations. In this review, case-by-case reaction modes and mechanisms are summarized and discussed, along with a personal perspective. Various organocopper intermediates were produced from the single-electron reduction of alkyl halides, capturing radicals from the oxidation of carbon-hydrogen bonds, transmetalation, and active copper species addition to unsaturated bonds (active Cu–H, Cu–Bpin or Cu–Si intermediate), and then, different organocopper intermediates can result from nucleophilic quenching, electrophilic quenching, transmetalation, isomerization to carbene, etc.

Hydrogen is a promising clean and renewable energy source; however, its efficient storage is one of the key challenges in establishing the sustainable hydrogen economy. The light main group metals and their tetrahydroborates and tetrahydroaluminates show great potential for high hydrogen storage capacity close to ambient conditions; however, their high hydrogenation and dehydrogenation temperatures, sluggish kinetics, and limited reversibility have always been an obstacle for practical applications. Large efforts have been devoted to modifying the thermodynamic and kinetic properties of these systems, and reviewing these efforts and highlighting future directions are the aims of the present review. Based on recent research, the application of multicomponent systems utilizing multiple modification methods, such as catalysis, nanoconfinement, alloying, and structure engineering, is essential for enhancing the storage conditions. The synergistic effect of multiple catalysts is now a key requirement to address various steps of the overall process, including forming/breaking the H–H and metal–H bonds, transporting hydrogen and heat, and suppressing the formation of side products. Compared to pristine systems, tremendous improvement has been achieved. Catalysed AlH₃ decomposition can now operate as a one-way hydrogen source below 100 °C and the Mg/MgH₂ hydrogen storage system exhibits good cyclic performance at elevated temperatures. Metal hydrides, tetrahydroborates, tetrahydroaluminates, and their composite systems face challenges in achieving close to ambient operating conditions and cyclic stability. As the demand for improved hydrogen energy storage is expected to grow, further research for the enhancement of these systems will continue to advance the state of hydrogen storage technology.

Heterogeneous molecular Fe–N–C catalysts hold promise for the oxygen reduction reaction (ORR), but their stability in acidic media remains a bottleneck. Here, we report the synthesis of a self-renewal Fe–N–C catalyst by uniformly polymerizing an iron polyphthalocyanine (FePPc) shell around carbon nanotubes (CNTs) via a microwave-assisted method. This FePPc/CNT catalyst achieves a much higher Fe mass loading (2.92 wt%) compared to directly depositing iron phthalocyanine (FePc) molecules on CNTs (FePc/CNT, 0.80 wt%) while maintaining a similar density of exposed Fe–N₄ sites to electrolytes. FePPc/CNT exhibits superior ORR activity in 0.1 M HClO₄ electrolyte with a half-wave potential (E_1/2) of 0.74 V (vs. reversible hydrogen electrode), a low Tafel slope of 51 mV dec⁻¹, and a high turnover frequency (TOF) of 0.98 site⁻¹ s⁻¹. Density functional theory (DFT) calculations attribute this enhanced activity to strong FePPc–CNT interactions that facilitate efficient electron transfer and favorable reaction energetics. Critically, FePPc/CNT demonstrates enhanced stability in the acidic electrolyte, retaining ∼80% of its initial current density after 24 h of the chronoamperometric test, outperforming FePc/CNT (42% after 5 h) and physically mixed FePPc and CNTs (49% after 24 h). Quantitative analysis reveals a unique self-renewal mechanism involving layer-by-layer shedding of FePPc, which exposes fresh active sites to sustain catalytic activity. At the same time, detached FePPc fragments sediment on CNTs. Furthermore, leached Fe ions migrate onto CNTs and aggregate into FeO_x nanoclusters, eventually leading to irreversible deactivation. These findings provide new insights for designing durable Fe–N–C catalysts for various reactions.

The practical deployment of an anion exchange membrane water electrolyzer (AEMWE) relies on the exploration of active and durable electrocatalysts towards the sluggish oxygen evolution reaction (OER). Although amorphous NiFe-based catalysts (a-NiFeO_xH_y) emerge as the competitive candidate due to impressive intrinsic OER activity, their unique defective structure renders the metal sites more susceptible to over-oxidation and dissolution, leading to poor stability. To address this challenge, we incorporate borate groups (BO₃³⁻) into the a-NiFeO_xH_y lattice by occupying the oxygen vacancy sites. The bridged borates not only maintain the structural stability via filling the oxygen vacancies, but also assist electron transfer from Ni to Fe to suppress Fe ion dissolution, thereby enhancing the catalytic stability of a-NiFeO_xH_y. Moreover, the tailored electronic structure of Ni favors electrochemical reconstruction to high-valence Ni active species and optimizes adsorption of oxygen intermediates towards superior OER activity. Therefore, a-B-NiFeO_xH_y integrated into the AEMWE can deliver a noteworthy current density of 4.75 A cm⁻² at a voltage of 2.0 V and maintain stable operation at 0.5 A cm⁻² for 3000 hours. This study not only affords a promising electrocatalyst for the AEMWE, but also paves a new avenue to break the activity-stability trade-off of amorphous materials for the OER.

Electrochemical nitrate reduction (ENR) is an appealing method for remediating nitrate contamination in wastewater and producing ammonia using renewable electricity. However, a mechanistic understanding of coupled mass transfer and electrocatalysis at the electrode–electrolyte interface, which dictates ENR efficiency, is limited. In this study, we develop an experimentally-validated multiphysics model of the Stern, diffuse, and diffusion layers near the surface of a polycrystalline titanium catalyst to investigate the effect of the electric double layer on ENR. The developed model couples the generalized-modified-Nernst–Planck equation with Frumkin–Butler–Volmer kinetics and numerical optimization to quantify the effect of applied potential and bulk electrolyte concentration on the ammonia formation rate. Our results reveal how dynamic driving forces at the polarized interface give rise to experimentally observed trends in ENR. Guided by this insight, we show that a more negative potential-of-zero-charge increases the limiting current density for ammonia synthesis by enabling faster migration of nitrate towards the cathode surface. The results motivate the development of multi-scale models that link transport phenomena with molecular-scale modelling to design and tailor interfaces for efficient ENR.