Co anchored on porphyrinic triazine-based frameworks with excellent biocompatibility for conversion of CO2 in H2-mediated microbial electrosynthesis

Microbial electrosynthesis is a promising alternative to directly convert CO₂ into long-chain compounds by coupling inorganic electrocatalysis with biosynthetic systems. However, problems arose that the conventional electrocatalysts for hydrogen evolution may produce extensive by-products of reactive oxygen species and cause severe metal leaching, both of which induce strong toxicity toward microorganisms. Moreover, poor stability of electrocatalysts cannot be qualified for long-term operation. These problems may result in poor biocompatibility between electrocatalysts and microorganisms. To solve the bottleneck problem, Co anchored on porphyrinic triazine-based frameworks was synthesized as the electrocatalyst for hydrogen evolution and further coupled with Cupriavidus necator H16. It showed high selectivity for a four-electron pathway of oxygen reduction reaction and low production of reactive oxygen species, owing to the synergistic effect of Co–N_x modulating the charge distribution and adsorption energy of intermediates. Additionally, low metal leaching and excellent stability were observed, which may be attributed to low content of Co and the stabilizing effect of metalloporphyrins. Hence, the electrocatalyst exhibited excellent biocompatibility. Finally, the microbial electrosynthesis system equipped with the electrocatalyst successfully converted CO₂ to poly-β-hydroxybutyrate. This work drew up a novel strategy for enhancing the biocompatibility of electrocatalysts in microbial electrosynthesis system.     

茴香醛的电合成研究

用氯仿作溶剂，在２０～４０℃下Ｃｅ（Ⅳ）电解液可将对甲基苯甲醚氧化成茴香醛，产率≥８４％，含量９８．３％。铈盐电解液反复使用１０次后，电解过程的Ｃｅ（Ⅳ）产率≥８０％，平均电流效率仍在５５％以上。     

Pyridine-N-rich Cu single-atom catalyst boosts nitrate electroreduction to ammonia

Nitrate-to-ammonia electroreduction (NO₃RR) offers a sustainable alternative to the energy-extensive Haber–Bosch process. Previous studies have reported nitrogen-coordinated copper single-atom catalysts with impressive activity and selectivity. However, regulating the nitrogen coordination structure at the atomic scale and its impact on the catalytic mechanism are not yet clear. This work demonstrates a pyridinic-N-rich copper single-atom catalyst (PR-CuNC) derived from semi-interpenetrating polypyrrole-polyethyleneimine hydrogels for the NO₃RR. By contrast to the catalyst with insufficient pyridinic nitrogen, PR-CuNC exhibits a maximum NH₃ Faraday efficiency of 94.61 % and a yield rate of 130.71 mg_NH3 mg_Cu⁻¹ h⁻¹ (3.74 mg_NH3 h⁻¹ cm⁻²). Theoretical evidence reveals that different N coordination types significantly affect the electronic structures of CuN₄ sites, resulting in the enhanced intrinsic activity. Our results show that the nitrogen structure is highly relevant to the performance of NO₃RR, underlining the importance of directly regulating the local coordination environment at the molecular level.     

Single-Atom Catalysts for H2O2 Electrosynthesis via Two-Electron Oxygen Reduction Reaction

Oxygen reduction reaction via the two-electron route (2e⁻ ORR) provides a green method for the direct production of hydrogen peroxide (H₂O₂) along with in situ utilization. The effective catalysts with high ORR activity, 2e⁻ selectivity, and stability are essential for the application of this technology. Single-atom catalysts (SACs) have attracted intensively attention for H₂O₂ electrosynthesis owing to the unique geometric and electronic configurations. In this review, the mechanism and theoretical predictions for 2e⁻ ORR over SACs are first introduced. Then, the recent advances of various SACs for the electrosynthesis of H₂O₂ are documented. And the correlation between the central atom, coordination atoms, and coordination environment of SACs and the corresponding electrocatalytic ORR performance including activity, selectivity, and stability are emphatically analyzed and summarized. Finally, the major challenges and opportunities regarding the future design of SACs for the H₂O₂ production are pointed out.     

C─N Coupling Enabled by N─N Bond Breaking for Electrochemical Urea Production

Urea electrosynthesis under mild conditions has emerged as a promising alternative strategy to replace the harsh industrial HaberBosch process, which is however limited by sluggish C N coupling and low selectivity. Here, a novel mechanism based on the synergistic effect of N N bond cleavage and C N coupling for highly efficient urea production is proposed. It is found that dual vanadium atoms anchoring onto defective graphene (V₂N₆) can activate the adsorbed *N₂, in which the stable N≡N bond can be gradually weakened until being broken after two protonation steps, with superior thermodynamic and kinetic feasibility. CO molecules can be easily adsorbed on the dissociated *NH, followed by an exothermic C N coupling to form the urea precursor *NHCONH with a low kinetic energy barrier of 0.20 eV. The dual-atom V₂N₆ not only exhibits superior intrinsic activity for urea formation, with a limiting potential of −0.26 V, but also can significantly suppress the competitive N₂ reduction and hydrogen evolution reactions. This study presents a new avenue for developing novel mechanisms and efficient catalysts for urea electrochemical synthesis.     

聚甲基丙烯酸羟乙酯/乙二醛交联体系的溶液-凝胶-溶液转变研究

聚合物凝胶的溶液-凝胶（sol-gel）/凝胶-溶液（gel-sol）转变通常依赖于外界条件（温度、pH等）的变化，但构建可在恒定条件下实现sol-gel-sol转变的凝胶体系依然是一个挑战。本文基于聚甲基丙烯酸羟乙酯（PHEMA）、乙二醛（GX）和N,N-二甲基甲酰胺（DMF）成功构建了一种恒温自发随时间进行sol-gel-sol转变的聚合物凝胶体系（HGX）。通过改变GX的含量、温度等条件，可对HGX的成胶时间、凝胶强度及降解时间进行调控。结果表明，不同条件下HGX可在10~1500 min内形成弹性模量可达847 Pa的凝胶，然后在1.5 h到＞15 d后降解为低粘液体（＜30 mPa·s）。并利用红外光谱和凝胶色谱揭示了sol-gel-sol转变的内在机理是缩醛反应和酯基断键的动态竞争所致。     

Ammonia Electrosynthesis with a Stable Metal-Free 2D Silicon Phosphide Catalyst

Metal-free 2D phosphorus-based materials are emerging catalysts for ammonia (NH₃) production through a sustainable electrochemical nitrogen reduction reaction route under ambient conditions. However, their efficiency and stability remain challenging due to the surface oxidization. Herein, a stable phosphorus-based electrocatalyst, silicon phosphide (SiP), is explored. Density functional theory calculations certify that the N₂ activation can be realized on the zigzag Si sites with a dimeric end-on coordinated mode. Such sites also allow the subsequent protonation process via the alternating associative mechanism. As the proof-of-concept demonstration, both the crystalline and amorphous SiP nanosheets (denoted as C-SiP NSs and A-SiP NSs, respectively) are obtained through ultrasonic exfoliation processes, but only the crystalline one enables effective and stable electrocatalytic nitrogen reduction reaction, in terms of an NH₃ yield rate of 16.12 µg h⁻¹ mg_cat.⁻¹ and a Faradaic efficiency of 22.48% at −0.3 V versus reversible hydrogen electrode. The resistance to oxidization plays the decisive role in guaranteeing the NH₃ electrosynthesis activity for C-SiP NSs. This surface stability endows C-SiP NSs with the capability to serve as appealing electrocatalysts for nitrogen reduction reactions and other promising applications.