Chinese Journal of Catalysis最新文献

The surface structures of heterogeneous catalysts significantly impact catalytic performance, especially for structure-sensitive reactions. In this study, we employed surface techniques such as low-energy ion scattering spectroscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy with CO as a probe (CO-FTIR) to investigate the surface dynamics of Rh/Al₂O₃ catalysts for propane dehydrogenation (PDH). We observed a notable induction process for PDH on Rh/Al₂O₃ catalysts, marked by significant variations in propane conversion, methane, and propylene selectivities. These changes were attributed to substantial coke formation. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy) and CO-FTIR revealed the coexistence of Rh nanoparticles, clusters, and single atoms on the surface. Through various dynamic quasi in-situ characterizations, we found that coke preferentially covered Rh clusters, thereby inhibiting C–C bond breaking and methane formation. Meanwhile, Rh single atoms were less affected by coke coverage and remained exposed as active and selective sites for PDH, favoring propylene production. This work underscores the sensitivity of PDH to the sizes of Rh species, with isolated Rh single atoms promoting propylene formation.

Electrocatalytic reduction of nitrate to ammonia (NITRR) is a promising strategy to remove nitrate pollutants and generate ammonia under mild conditions. However, the low conversion rate of nitrate and insufficient ammonia production rate severely limits the development of NITRR. Manipulating the adsorption of N-intermediates on the surface of catalyst greatly affects the activity and the selectivity of catalytic reaction. Herein, four one-dimensional π-d conjugated coordination polymers (1D CCPs) are synthesized and applied to NITRR. The selectivity and activity of NITRR are well improved by metal ion substitutions, which regulate the adsorption towards generated intermediates. The ammonia production rate reaches 2.28 mg h^–1 cm^–2 over Cu-BTA in 2 h, comparable to recent works at low nitrate concentrations, and the conversion rate of nitrate up to 96.74% in four hours with 79.46% ammonia selectivity. Density functional theory calculations reveal that Cu-BTA had electron-richer Cu center, causing the enhanced free energy of *NO and the attenuation of N=O bond. Therefore, the ΔG required for converting *NO to *NHO is reduced and the further hydrogenation is promoted. Additionally, the adsorption energies toward NH₃ are also effectively reduced by metal ions substitution, accelerating the desorption of generated and adsorbed NH₃, making the turnover of catalysts more frequent.

Increasing global energy consumption and environmental pollution make the use of new energy sources and environmentally friendly technologies essential to meet the diverse needs of industries. Photoelectrocatalysis is a promising method of utilising solar and electrical energy for various catalytic reactions with significant environmental and energy saving benefits. And photoelectrocatalytic (PEC) oxygen evolution reaction (OER) and CO₂ reduction reaction (CO₂RR) are two catalytic reactions with great potential for energy and environmental applications. PEC OER is critical for renewable energy technologies for water oxidation and other related oxidation reactions. PEC CO₂RR converts carbon dioxide into high-value products via a catalyst, enabling the rational use of carbon dioxide and the reduction of greenhouse gas emissions. Both technologies are efficient, environmentally friendly, and sustainable. However, further research and optimisation are needed to promote the industrial application of both technologies for energy conversion and environmental protection. This paper reviews the research progress of PEC CO₂RR and OER catalysts in recent years, including detailed descriptions of catalyst types, reaction mechanisms and performance tests. Finally, the paper considers the future trends and prospects of PEC technology, providing new insights into the technology and research directions for PEC OER and CO₂RR catalysts.

Non-heme Fe(II)/α-ketoglutarate (αKG)-dependent enzymes catalyze numerous C–H activation and functionalization reactions. However, how αKG-dependent non-heme enzymes catalyzed C–H functionalization beyond the hydroxylation is largely unknown. Here, we addressed this issue in Fe(II)/ αKG-dependent oxygenase TqaL_Nc, which catalyzes the selective C–H amination but bypasses the thermodynamically favored C–H hydroxylation. Here, the extensive computational studies have shown that the aziridine formation involves the conformational change of the Fe(IV)=O species from the axial configuration to the equatorial one, the substrate deprotonation of NH₃⁺ group to form the NH-ligated intermediate, the C–H activation by the equatorial Fe(IV)=O species. Such mechanistic scenario has been cross-validated by oxidation of various substrates by TqaL_Nc and its variants, including the available experiments and our new experiments. While the presence of steric hindrance between the substrate and the second-sphere residues would inhibit the aziridination process, the intrinsic reactivity of aziridination vs. hydroxylation is dictated by the energy splitting between two key redox-active dπ* frontier molecular orbitals: dπ*_Fe-N and dπ*_Fe-OH. The present findings highlight the key roles of the coordination change and dynamics of iron cofactor in dictating the catalysis of non-heme enzymes and have far-reaching implications for the other non-heme Fe(II)/αKG-dependent enzymes catalyzed C–H functionalization beyond the hydroxylation.

Electrocatalytic CO₂ reduction reaction (CO₂RR) holds significant promise for sustainable energy conversion, with cobalt phthalocyanine (CoPc) emerging as a notable catalyst due to its high CO selectivity. However, CoPc's efficacy is hindered by its limited ability to provide sufficient proton for the protonation process, particularly at industrial current densities. Herein, we introduce defect-engineered carbon nanotubes (d-CNT) to augment proton feeding for CO₂RR over CoPc, achieved by expediting water dissociation. Our kinetic measurements and in-situ attenuated total reflection surface-enhanced infrared absorption spectroscopy reveal d-CNT significantly enhances proton feeding, thereby facilitating CO₂ activation to *COOH in CoPc. Density functional theory calculations corroborate these findings, illustrating that d-CNT decreases the barrier to water dissociation. Consequently, the CoPc/d-CNT mixture demonstrates robust performance, achieving 500 mA cm^–2 for CO₂RR with CO selectivity exceeding 96%. Notably, CoPc/d-CNT remains stability for a duration of 20 h under a substantial current density of 150 mA cm^–2. The study broadens the scope of practical applications for molecular catalysts in CO₂RR, marking a significant step towards sustainable energy conversion.

Electrochemical NO reduction reaction (NORR) toward NH₃ synthesis emerges as a promising approach to eliminate NO pollution and generate high-value-added products simultaneously. Therefore, exploring suitable NORR electrocatalysts is of great importance. Here, we present a design principle to evaluate the activity of single-atom alloy catalysts (SAACs), whose excellent catalytic performance and well-defined bonding environments make them suitable candidates for studying structure-activity relationships. The machine learning (ML) algorithm is chosen to unveil the underlying physics and chemistry. The results indicate that the catalytic activity of SAACs is highly correlated with the local environment of the active center, that is, the atomic and electronic features. The coeffect of these features is quantitatively verified by adopting a data-driven method. The combination of density functional theory (DFT) and ML investigations not only provides an understanding of the complex NORR mechanisms but also offers a strategy to design highly efficient SAACs with specific active centers rationally.

High-entropy alloy (HEA) catalysts exhibit enhanced hydrogen evolution reaction (HER) activity in water electrolysis, yet the understanding of their structure and active sites in reaction environments remains unclear. Here, we systematically investigated the HER activity and stability of PtPdRhRuCu/C through a combination of electrochemical measurements, in situ synchrotron radiation X-ray absorption spectroscopy (XAS) at the Cu K-edge and Pt L₃-edge, and density functional theory (DFT) calculations. Uniformly sized PtPdRhRuCu HEA nanoparticles were prepared via a facile one-step solvothermal method. In situ XAS results revealed that the HEA nanoparticles maintained metallic states and a disordered arrangement of the overall structure at hydrogen evolution potential, implying the absence of the separated phases. Relying on multi-metal active sites, PtPdRhRuCu/C demonstrated a remarkably low overpotential of 23.3 mV at 10 mA cm^–2 in alkaline HER, which is significantly lower than the overpotential observed in commercial Pt/C (50.3 mV), and achieving a mass activity 7.9 times that of Pt/C. DFT calculations show that the synergy of each metal site optimizes the dissociation energy barrier of water molecules. This study not only demonstrates the advancement of high-entropy alloys in electrocatalysis but also provides a comprehensive understanding of the structure-activity relationship of these unique catalysts through detailed characterizations. Our findings further contribute to the rational design and application of high-entropy alloy catalysts, specifically in HER.

NiFe-based (oxy)hydroxides are among the most efficient electrocatalysts for the oxygen evolution reaction (OER). However, significant Fe leakage during the OER results in unsatisfactory stability. Herein, a large-current (1.5 A cm^–2) galvanostatic reconstruction was used to fabricate FeOOH@NiOOH (eFNO_L) with both fixed Fe sites and exposed high-index crystal facets (HIFs). Compared to FeNiOOH with low-index crystal facets, the phase-separated FeOOH@NiOOH showed a higher binding energy towards Fe, and the HIFs significantly improved the catalytic activity of FeOOH. The optimized eFNO_L catalyst exhibits ultralow overpotentials of 234 and 272 mV, yielding substantial current densities of 100 and 500 mA cm^–2, respectively, with a small Tafel slope of 35.2 mV dec^–1. Moreover, due to the stabilized Fe sites, its striking stability over 100 h at 500 mA cm^–2 with 1.5% decay outperforms most NiFe-based OER catalysts reported recently. This study provides an effective strategy for developing highly active and stable catalysts via large-current electrochemical reconstruction.

Recently, electrochemical nitrate reduction reaction (NO₃RR) has been intensively explored for the synthesis of ammonia, and copper (Cu) has become one of the most promising materials for NO₃RR. Notably, Cu is an important plasmonic metal that absorbs visible light. The plasmonic effect might have a significant influence on the performance of Cu-catalyzed NO₃RR but has been seldom reported. Herein, we report the synergistic photoelectric and thermal effect for efficient and stable NO₃RR on plasmonic Cu nanowire photocathodes, which is exclusively effective for NO₃RR but has no effect on the competing hydrogen evolution reaction. The faradaic efficiency for ammonia production is nearly 100% within a potential range from –0.2 V to –0.4 V vs. RHE, and a high ammonia yield rate of 1.37 mmol h^–1 cm^–2 is achieved at –0.2 V vs. RHE. Further operando photoelectrochemical studies and theoretical simulations confirm that the plasmonic excitation efficiently accelerates the rate-limiting desorption of NH₃ on Cu surfaces. We further demonstrate the versatility of this strategy to other Cu-based nanostructures.

Tuning oxygen vacancy (V_O) in metal oxides catalysts that efficiently activates O₂ molecule to promote oxidation reactions remains challenging. Herein, transition metal (M = Mn, Co, and Mo) doping was used to moderate the coordination environment of V_O in La₂FeMO₆ and promote activity for selective oxidation of hydrogen sulfide (H₂S). Various techniques reveal that the introduction of Mn and Co forms the homogeneous double perovskite phase, which results in the formation of asymmetric V_O. Although these asymmetric V_O are more difficult to form than symmetric Fe-V_O-Fe due to the shorter bond distance and stronger bond strength of Fe-O, they are more conducive to the dissociation of O₂ molecules. Among them, the formed rich Fe-V_O-Mn sites from the alternate substitution of Mn to Fe boosted the activation of O₂ molecules of Mn-substituted LaFeO₃. Therefore, enhanced catalytic activity and outstanding sulfur selectivity were achieved as a result of promoted oxygen mobility and reducibility. This work provides an attractive strategy for rational design of advanced oxidation catalysts.