Selective Production Research Articles

C2H2 selective hydrogenation over metal-doped CeO2 catalysts: Unraveling the role of metal and surface frustrated Lewis acid-base pair in tuning catalytic performance

Doping the second metal into CeO2 is used as a generally regarded strategy to promote C2H2 selective hydrogenation. This work employs DFT calculations and microkinetic modeling to explore the performance of CeO2 doped with different Cu, Ni, Pd, Pt, or Co atom towards C2H2 selective hydrogenation. The results show that the doped metal not only promotes the formation of surface oxygen-vacancy, but also generate different types of FLPs with surface O atom. FLPs promote H2 heterolytic dissociation to produce Ce-H/M-H and O-H species. Different forms of surface H species affect the performance of C2H2 selective hydrogenation. C2H4 selectivity follows a U-shaped dependence on surface Ce atom charge transfer amount. The screened catalyst Co/CeO2 presents excellent C2H4 production activity and selectivity, which could well prevent the generation of green oil. This work provides new insights for designing highly efficient metal-doped CeO2 catalysts by tuning the doped metal type.

In Situ Etching-Hydrolysis Strategy To Construct an In-Plane ZnIn2S4/In(OH)3 Heterojunction with Enhanced CO2 Photoreduction Performance.

The in-plane heterojunctions with atomic-level thickness and chemical-bond-connected tight interfaces possess high carrier separation efficiency and fully exposed surface active sites, thus exhibiting exceptional photocatalytic performance. However, the construction of in-plane heterojunctions remains a significant challenge. Herein, we prepared an in-plane ZnIn2S4/In(OH)3 heterojunction (ZISOH) by partial conversion of ZnIn2S4 to In(OH)3 through the addition of H2O2. This in situ oxidation etching-hydrolysis approach enables the ZISOH heterojunction to not only preserve the original nanosheet morphology of ZnIn2S4 but also form an intimate interface. Moreover, generated In(OH)3 serves as an electron-accepting platform and also promotes the adsorption of CO2. As a result, the heterojunction exhibits a remarkably enhanced performance for photocatalytic CO2 reduction. The production rate and selectivity of CO reach 1760 μmol g-1 h-1 and 78%, respectively, significantly higher than those of ZnIn2S4 (842 μmol g-1 h-1 and 65%). This work puts forward a feasible and facile approach to construct in-plane heterojunctions to enhance the photocatalytic performance of two-dimensional metal sulfides.

Tetracycline degradation through selective activation of molecular oxygen by a fluidic sequential photoelectro-Fenton system

The heterogeneous Fenton-like process is regarded as a promising strategy for reactive oxygen species (ROS) production by driving a two-electron oxygen reduction reaction toward H2O2 and stepping activating the as-generated H2O2 to ROS. Therefore, a fluidic sequential photoelectro-Fenton (PEF) system was developed for the selective activation of molecular oxygen to generate ROS. The system comprises a hydrogen peroxide (H2O2) electrolyzer and a photocatalytic membrane reactor (PCMR). The H2O2 electrolyzer employed a PEI-O/CNT air self-diffusion electrode to achieve high selectivity for H2O2 production without aeration. In the subsequent stage, within the PCMR, two-dimensional Fe/C3N4 with a nanoconfinement structure selectively converted H2O2 into ROS. The exceptional tetracycline (TC) degradation efficiency (96.0 %) was attributable to the synergistic effects of radical and non-radical pathways. The fluidic sequential PEF system achieved efficient and energy-saving H2O2 production (0.134 kWh/g of H2O2) and TC degradation (1.7 kWh/kg of TC). In addition, the PEF system not only has a good effect on removing tetracycline in real water but also can effectively remove a variety of antibiotic pollutants, which has a good prospect for practical application. This research contributed new insights into the development of the fluidic sequential PEF process.

Membraneless organelles assembled by AuNPs-enzyme integration in non-photosynthetic bacteria: Achieving high specificity and selectivity for solar hydrogen production

The emergence of semiartificial photosynthesis holds great promise for improving light energy capture and conversion efficiency. However, achieving high product specificity and selectivity in semiartificial photosynthetic systems remains a challenge. In this study, we employed genetic engineering techniques to construct a membraneless organelle in E. coli, serving as the photoreaction carrier. The self-assembly of photosensitizers and hydrogenase within the carrier has successfully established a semiartificial photosynthetic model characterized by high product specificity and selectivity. In this model system, electrons were directly transferred to hydrogenase upon AuNPs light excitation in membraneless organelle, eliminating the need for additional electron mediators and bypassing the use of intracellular NADH/NAD+ as a reducing agent to avoid byproduct formation. The semiartificial photosynthetic system demonstrated an 11782-fold and 40-fold increase in hydrogen production compared to bare AuNPs and the empty vector E. coli hybrid system, respectively. This membraneless organelle holds the potential to robustly support the specific synthesis of high-energy-density, value-added compounds through solar energy conversion.

Perovskite Oxide Catalysts for Enhanced CO2 Reduction: Embroidering Surface Decoration with Ni and Cu Nanoparticles

The imperative reduction of carbon dioxide into valuable fuels stands as a crucial step in the transition towards a more sustainable energy system. Perovskite oxides, with their high compositional and property adjustability, emerge as promising catalysts for this purpose, whether employed independently or as a supporting matrix for other active metals. In this study, an A-site-deficient La0.9FeO3 perovskite underwent surface decoration with Ni, Cu or Ni + Cu via a citric acid-templated wet impregnation method. Following extensive characterization through XRD, N2 physisorption, H2-TPR, SEM-EDX, HAADF STEM-EDX mapping, CO2-TPD and XPS, the prepared powders underwent reduction under diluted H2 to yield metallic nanoparticles (NPs). The prepared catalysts were then evaluated for CO2 reduction in a CO2/H2 = 1/4 mixture. The deposition of Ni or Cu NPs on the perovskite support significantly enhanced the conversion of CO2, achieving a 50% conversion rate at 500 °C, albeit resulting in only CO as the final product. Notably, the catalyst featuring Ni-Cu co-deposition outperformed in the intermediate temperature range, exhibiting high selectivity for CH4 production around 350 °C. For this latter catalyst, a synergistic effect of the metal–support interaction was evidenced by H2-TPR and CO2-TPD experiments as well as a better nanoparticle dispersion. A remarkable stability in a 20 h time-span was also demonstrated for all catalysts, especially the one with Ni-Cu co-deposition.

A Multi-Interface Structure of Graphdiyne/Cobalt Oxides for Chlorine Production.

A challenge facing the chlor-alkali process is the lack of electrocatalyst with high activity and selectivity for the efficient industrial production of chlorine. Herein the authors report a new electrocatalyst that can generate multi-interface structure by in situ growth of graphdiyne on the surface of cobalt oxides (GDY/Co3O4), which shows great potential in highly selective and efficient chlorine production. This result is due to the strong electron transfer and high density charge transport between GDY and Co3O4 and the interconversion of the mixed valence states of the Co atoms itself. These intrinsic characteristics efficiently enhance the conductivity of the catalyst, facilitate the reaction kinetics, and improve the overall catalytic selectivity and activity. Besides, the protective effect of the formed GDY layer is remarkable endowing the catalyst with excellent stability. The catalyst can selectively produce chlorine in low-concentration of NaCl aqueous solution at room temperature and pressure with the highest Faraday efficiency of 80.67% and an active chlorine yield rate of 184.40mg h-1 cm-2, as well as superior long-term stability.

Regulating Cu Oxidation State for Electrocatalytic CO2 Conversion into CO with Near-Unity Selectivity via Oxygen Spillover.

Cu-based catalysts are the most intensively studied in the field of electrocatalytic CO2 reduction reaction (CO2RR), demonstrating the capacity to yield diverse C1 and C2+ products albeit with unsatisfactory selectivity. Manipulation of the oxidation state of Cu sites during CO2RR process proves advantageous in modulating the selectivity of productions, but poses a formidable challenge. Here, an oxygen spillover strategy is proposed to enhance the oxidation state of Cu during CO2RR by incorporating the oxygen donor Sb2O4. The Cu-Sb bimetallic oxide catalyst attains a remarkable CO2-to-CO selectivity approaching unity, in stark contrast to the diverse product distribution observed with bare CuO. The exceptional Faradaic efficiency of CO can be maintained across a wide range of potential windows of ≈700mV in 1m KOH, and remains independent of the Cu/Sb ratio (ranging from 0.1:1 to 10:1). Correlative calculations and experimental results reveal that oxygen spillover from Sb2O4 to Cu sites maintains the relatively high valence state of Cu during CO2RR, which diminishes the binding strength of *CO, thereby achieving heightened selectivity in CO production. These findings propose the role of oxygen spillover in CO2RR over Cu-based catalysts, and shed light on the rational design of highly selective CO2 reduction catalysts.

UiO-67 metal-organic frameworks with dual amino/iodo functionalization, and mixed Zr/Ce clusters: Highly selective and efficient photocatalyst for CO2 transformation to methanol

Metal-organic frameworks (MOFs) are promising tools for photocatalytic CO2 reduction (PCR) to produce valuable added-value products. However, existing MOFs demonstrate significantly weaker potential for PCR to MeOH compared to fuels like CO, CHOOH, and CH4. This study address this challenge by exploring a series of bifunctional UiO-67 MOFs containing NH2 and I groups with varying Ce to Zr metal node ratios (0, 10, 20, 29, and 40 % Ce). These MOFs, denoted as Zr/CeX%-UiO-67(NH2, I), were probed for their ability to convert CO2 to MeOH under solar irradiation without the need for a photosensitizer. The results demonstrate a remarkable increase in both selectivity and efficiency for MeOH production with increasing Ce content. Notably, Zr/Ce29%-UiO-67(NH2, I) achieves 100 % selectivity for MeOH production, along with MeOH productivity of 44.7 µmolh−1g−1, significantly surpassing previously reported UiO-based MOFs for PCR-to-MeOH conversion. Furthermore, this MOF exhibits exceptional CO2 uptake capacity compared to pristine UiO-67 and many established MOFs, further highlighting its catalytic efficacy. The outstanding photocatalytic performance of Zr/Ce40%-UiO-67(NH2, I) can be attributed to a synergistic combination factors: (i) the optimal incorporation of redox-active Ce metal sites, (ii) enhanced CO2 capture facilitated by the cooperative interaction of NH2 and I groups, and (iii) the introduction of amino functions that broaden the light absorption range of the MOF. This work demonstrates a successful strategy for incorporating various functionalities into MOFs, paving the way for the design of highly selective and efficient PCR catalysts for MeOH production.

Hydrogen‐Bond‐Network Breakdown Boosts Selective CO2 Photoreduction by Suppressing H2 Evolution

AbstractConventional strategies for highly efficient and selective CO2 photoreduction focus on the design of catalysts and cocatalysts. In this study, we discover that hydrogen bond network breakdown in reaction system can suppress H2 evolution, thereby improving CO2 photoreduction performance. Photosensitive poly(ionic liquid)s are designed as photocatalysts owing to their strong hydrogen bonding with solvents. The hydrogen bond strength is tuned by solvent composition, thereby effectively regulating H2 evolution (from 0 to 12.6 mmol g−1 h−1). No H2 is detected after hydrogen bond network breakdown with trichloromethane or tetrachloromethane as additives. CO production rate and selectivity increase to 35.4 mmol g−1 h−1 and 98.9 % with trichloromethane, compared with 0.6 mmol g−1 h−1 and 26.2 %, respectively, without trichloromethane. Raman spectroscopy and theoretical calculations confirm that trichloromethane broke the systemic hydrogen bond network and subsequently suppressed H2 evolution. This hydrogen bond network breakdown strategy may be extended to other catalytic reactions involving H2 evolution.

Co-N-C axially coordination regulated H2O2 selectivity via water medicated recombination of solute •OH: A new route

The cobalt, earth abundant transition metal, embedded in nitrogen doped carbon material as single atom site (Co-N-C) has been manifested as promising electrochemical oxygen reduction reaction (ORR) catalyst, however the unsatisfying production selectivity has hampered its widespread applications. Herein, the H2O2 selectivity of Co-N-C catalyst has been tailored with Co axial functional groups. Thermodynamically, the selectivity is regulated due to the fine-tuning of the adsorption of the key reaction intermediates (ΔG*OOH), and five functional groups, including −O, –OH, –CN, −CH3 and −SO3, endow the Co-N-C catalyst with superior H2O2 selectivity. Importantly, we unravel a new water medicated recombination of solute •OH reaction pathway for H2O2 production, which was the result of dissociation of *HOOH in explicit water environment. That is, two •OH species reaction in the liquid environment which originated from the creaking of *OOH intermediates due to the weakened O-O bond by the interaction with surrounding water. This study provides foundational understanding for the ORR catalytic mechanism at the electrochemical interface and opens up new avenues for rational design of targeted high efficiency electrocatalysts.

Emerging Photoreforming Process to Hydrogen Production: A Future Energy

AbstractIn the quest of renewable energy technologies, solar photoreforming emerges as one of the affordable yet challenging process for converting biomass into hydrogen, hydrocarbon fuels, and chemicals. This review highlights the state‐of‐the‐art photoreforming, elucidating its underlying mechanisms for the conversion of dissipated polymers into H2 and valuable chemicals. Biomass feedstocks such as carbohydrates, agricultural residues, glycopolymers, food wastes, and waste plastics are evaluated based on their chemical composition, energy content, and sustainability aspects, exploring the selection of appropriate bio‐renewable resources, considering their abundance, availability, and potential for hydrogen production. The impact of diverse process parameters on photoreforming efficiency is explored, encompassing factors like reaction temperature, pH, catalyst loading, reactor design, solvent effect, and light intensity across various sacrificial substrates. The discussion also considers their correlation with hydrogen production rate, selectivity, and energy efficiency. This review buckles on the design and synthesis of functional photocatalysts for biomass‐derived feedstock, highlighting their photocatalytic (PC) properties in biomass reforming processes and related feedstock into valuable chemicals and biofuel. The review also delves into potential pathways for future advancements including artificial intelligence (AI) and machine learning (ML), alongside addressing the challenges and insightful perspectives within this evolving field of future green energy.

Possibility of hydrogen peroxide production by 2e− WOR with non-oxygen evolution catalysts and its application for organic dye decomposition via a self-cycled Fenton System

Production of H2O2 through two-electron-transfer water oxidation (2e− WOR) is an emerging prospecting green fuel preparation routine. Meantime, unveiling the relationship between the electronic structure and catalytic selectivity is the prerequisite for high H2O2 production selectivity. Up to now, the designed principle for the 2e− WOR catalysts relies on the modulation of the potential-dependent binding energy between the key intermediates (*OH, *O and *OOH) and the catalysts, presented as the activity volcano plots. In this study, for the first time, the d-band center theory was introduced as a theoretical guidance for the rational design of the 2e−WOR catalysts with selected Mo, Nb, W, Ta, Zr and Al oxides, evidencing the preferred H2O2 production in the metal oxides with no d-band active center. Besides, by optimizing the working conditions including pH and electrolyte, a new manner for the efficient water purification system enabled by the efficient 2e− WOR catalysts/system design is proposed.

Ru-Induced Defect Engineering in Co3O4 Lattice for High Performance Electrochemical Reduction of Nitrate to Ammonium.

Amidst these growing sustainability concerns, producing NH4 + via electrochemical NO3 - reduction reaction (NO3RR) emerges as a promising alternative to the conventional Haber-Bosch process. In a pioneering approach, this study introduces Ru incorporation into Co3O4 lattices at the nanoscale and further couples it with electroreduction conditioning (ERC) treatment as a strategy to enhance metal oxide reducibility and induce oxygen vacancies, advancing NH4 + production from NO3RR. Here, supported by a suite of ex situ and in situ characterization measurements, the findings reveal that Ru enrichment promotes Co species reduction and oxygen vacancy formation. Further, as evidenced by the theoretical calculations, Ru integration lowers the energy barrier for oxygen vacancy formation, thereby facilitating a more energy-efficient NO3RR-to-NH4 + pathway. Optimal catalytic activity is realized with a Ru loading of 10 at.% (named 10Ru/Co3O4), achieving a high NH4 + production rate (98nmols-1cm-2), selectivity (97.5%) and current density (≈100mAcm-2) at -1.0V vs RHE. The findings not only provide insights into defect engineering via the incorporation of secondary sites but also lay the groundwork for innovative catalyst design aimed at improving NH4 + yield from NO3RR. This research contributes to the ongoing efforts to develop sustainable electrochemical processes for nitrogen cycle management.

Synthetic Placement of Active Sites in MFI Zeolites for Selective Toluene Methylation to para-Xylene.

Brønsted acidic zeolites are ubiquitous catalysts in fuel and chemical production. Broadening the catalytic diversity of a given zeolite requires strategies to manipulate the acid site placement at framework positions within distinct microporous locations. Here, we combine experiment and theory to elucidate how intermolecular interactions between organic structure-directing agents (OSDAs) and framework Al centers influence the placement of H+ sites in distinct void environments of MFI zeolites and demonstrate the catalytic consequences of active site location on kinetically controlled (403 K) toluene methylation to xylene regioisomers. Kinetic measurements, interpreted using mechanism-derived rate expressions and transition state theory, alongside density functional theory (DFT) calculations show that larger intersection environments similarly stabilize all three xylene isomer transition states without altering well-established aromatic substitution patterns (ortho/para/meta ∼ 60%:30%:10%), while smaller channel environments preferentially destabilize transition states that form bulkier ortho- and meta-isomers, thereby resulting in high intrinsic para-xylene selectivity (∼80%). DFT calculations reveal that the flexibility of nonconventional OSDAs (e.g., 1,4-diazabicyclo[2.2.2]octane) to reorient within MFI intersections and their ability to hydrogen-bond to form protonated complexes favor the placement of Al in smaller channel environments compared to conventional quaternary OSDAs (e.g., tetra-n-propylammonium). These molecular-level insights establish a mechanistic link between OSDA structure, active site placement, and transition state stability in MFI zeolites and provide active site design strategies that are orthogonal to crystallite design approaches harnessing complex reaction-diffusion phenomena to enhance regioisomer selectivity in the industrial production of valuable polymer precursors.

Pauling-type adsorption of O2 induced by S-scheme electric field for boosted photocatalytic H2O2 production

The effective adsorption of oxygen (O2) molecules over photocatalysts is a critical step in promoting the performance of photocatalytic H2O2 production. However, g-C3N4 usually features a Yeager-type (side-on) adsorption configuration of O2 molecules, which causes the breaking of O–O bonds and severely hinders the H2O2 production activity. Herein, we synthesized an oxygen-vacancy-rich TiO2–x/g-C3N4 step-scheme (S-scheme) heterojunction to regulate the oxygen adsorption configuration and improve the 2e– ORR selectivity of H2O2 production. In-situ X-ray photoelectron spectroscopy (in-situ XPS) and density functional theory (DFT) calculations reveal that the S-scheme heterojunction is formed between TiO2–x and g-C3N4. The difference between their Fermi levels leads to the electron flow from g-C3N4 to TiO2–x, which increases the electron-deficient sites in g-C3N4. As a result, the cleavage of O–O bonds on the surface of g-C3N4 is avoided and the oxygen adsorption configuration is tuned from Yeager-type to Pauling-type (end-on). Consequently, the photocatalytic H2O2 production rate is dramatically improved to 1780.3 μmol h–1, which is about 5 times higher than that of pristine g-C3N4. This work paves a new way to tailor the oxygen adsorption configuration by rationally designing S-scheme heterojunction photocatalysts.

A quadruple transition metal dichalcogenide for variously synergetic electron behaviors during photocatalytic carbon dioxide reduction

A quadruple 2H transition metal dichalcogenide of platinum doped molybdenum selenide sulfide (MoSSe) has been achieved. The critical doping amount of Pt is estimated to be approximately 0.9 a.t.% to prevent the formation of a heterogeneous phase. It has been observed that the excess Pt beyond this critical doping level cannot be settled into the lattice of MoSSe but forms an independent metal phase of Pt nanoparticles, composing a heterostructure with MoSSe, in which the behavior of photogenerated electrons will be predominantly governed by metal Pt and transported along the pathways for gas production in the photocatalytic CO2 reduction. However, as long as Pt can be located in the lattice of MoSSe, the elemental variety of Pt doped MoSSe has provided various active sites during the photocatalytic CO2 reduction process, favoring the localized coupling of matching intermediates, consequently enhancing the production of high value-added liquid products. In essence, the successful integration of Pt into the 2H MoSSe lattice opens up diverse active sites, optimizing the photocatalytic performance on the selectivity of liquid production reduced from CO2.

Acetone-Butanol-Ethanol (ABE) fermentation with clostridial co-cultures for enhanced biobutanol production

This study has addressed the issue of enhanced biobutanol production through Consolidated Bioprocessing, with the use of clostridial co-cultures combining C. acetobutylicum (Cac) and C. pasteurianum (Cpa). To begin with, the total Acetone-Butanol-Ethanol (ABE) solvent production and butanol selectivity of individual clostridial cultures grown on different carbon sources present in lignocellulosic hydrolysates. Thereafter, statistical optimization of ABE fermentation with co-culture system was carried out using Box-Behnken design. The optimization variables were Cac to Cpa inoculum ratio (X1 in mL mL−1), sodium concentration in the medium (X2 g L−1), and xylose/glucose ratio (X3 g g−1 L L−1), whereas response variables were butanol titre (Y1 in g L−1), biomass growth (Y2 OD600), total ABE titre (Y3 in g L−1). Maximum values of the response variables with the corresponding set of optimization parameters were as follows: Y1, max = 12.1 ± 0.45 (for X1 = 0.30, X2 = 5.90, X3 = 0), Y2, max = 4.15 ± 0.03 (for X1 = 0.3, X2 = 2.42, X3 = 0.14), Y3, max = 23.1 ± 0.55 (for X1 = 0.46, X2 = 6.36, X3 = 0). The study demonstrated a substantial ≈ 22% and 61% increment in butanol titre in co-culture system compared to individual fermentations with Cac and Cpa grown on pure glucose, respectively.

New Design PdNi Heterogeneous Nanocatalysts for the Direct Synthesis of Hydrogen Peroxide

Hydrogen peroxide (H2O2) is a widely used chemical as an eco-friendly oxidizing agent, with water being the only byproduct of oxidation in applications like bleaching pulp and paper, making electronic semiconductors, chemical and detergent synthesis, and wastewater treatment. The direct synthesis approach is preferred to provide the environmentally friendly production of H2O2 for market requirements. Bimetallic PdNi nanocatalysts were chosen for this study because of their catalytic activity and the structural characteristics of the material system. First, for the development of order-structured bimetallic PdNi nanocatalysts based on mesoporous carbon template after hydrogen-assisted heat treatment at 750∘C. The transformation of the disordered structure into ordered intermetallically structured PdNi alloys with higher alloying extents was confirmed by X-ray absorption spectroscopy (XAS) and high-resolution transition electron microscopy (HR-TEM). Then, to improve the oxygen oxidation reaction, two-electron pathway selectivity was used by TiO2-C as a support-ordered structure material to facilitate strong metal-support interactions. XAS and X-ray photoelectron spectra (XPS) techniques show more clear evidence of metal-support interactions with electron transfer from defects in the TiO2-C support to the ordered alloyed PdNi nanocatalysts, resulting in record productivity and selectivity of H2O2 production at ambient conditions. The results demonstrated in this study will enlighten a reliable design of new heterogeneous nanocatalysts with ordered structure. Electron transfer between hybrid support and active sites can clarify the catalytic behavior and prompt further research during the direct synthesis of hydrogen peroxide.
 Keywords: hydrogen peroxide, direct synthesis, heterogeneous nanocatalysts PdNi, TiO2-C

Electrochemical oxidation of ammonia in water by Pt/NbC membrane-based catalytic nanofluid reactor

Electrochemical oxidation has garnered increasing attention for its potential in treating ammonia in wastewater. However, achieving both high conversion and high nitrogen selectivity simultaneously, while maintaining a short hydraulic retention time (HRT), remains a significant challenge. In this study, we constructed an efficient niobium carbide (NbC) nanoporous membrane reactor by incorporating metal platinum as a catalyst for the electrochemical oxidation of ammonia. The electrocatalytic oxidation process occurred within the nanochannels of the membrane. This design allowed for enhanced single-pass removal of ammonia due to the short diffusion distance on the nanometer scale, which subsequently increased the mass transfer efficiency. Remarkably, we achieved highly controllable pore sizes in the NbC membrane, ranging from 200 to 8.3 nm by dip-coating method. Without the addition of any oxidants, the single-pass removal of ammonia reached 100 % when the applied potential was set at 4 V vs. SCE on a membrane with a pore size of 8.3 nm, and an HRT of 249 s. The primary product obtained from this process was nitrogen, displaying a selectivity of 88.09 %, with a small percentage of nitrate production (selectivity of 11.91 %). By decreasing the applied potential or increasing the pore size, the selectivity of nitrogen can be further improved, reaching 100 %. However, this adjustment may lead to a decrease in the conversion of ammonia. DFT results have revealed that the production of nitrogen on the Pt (111) surface occurs through the NH4+→NH3 → NH2 → N → N2 pathway. This finding contributes to the understanding of the electrochemical process for ammonia removal in water, and provides a viable option for the design of efficient nanomembrane reactors.

Photocatalytic Optical Hollow Fiber with Enhanced Visible-light-driven CO2 Reduction.

A visible-light-driven CO2 reduction optical fiber is fabricated using graphene-like nitrogen-doped composites and hollow quartz optical fibers to achieve enhanced activity, selectivity, and light utilization for CO2 photoreduction. The composites are synthesized from a lead-based metal-organic framework (TMOF-10-NH2) and g-C3N4 nanosheet (CNNS) via electrostatic self-assembly. The TMOF-10-NH2/g-C3N4 (TMOF/CNNS) photocatalyst with an S-type heterojunction is coated on optical fiber. The TMOF/CNNS coating, which has a bandgap energy of 2.15eV, has good photoinduced capability at the coating interfaces, high photogenerated electron-hole pair yield, and high charge transfer rate. The conduction band potential of the TMOF/CNNS coating is more negative than that for CO2 reduction. Moreover, TMOF facilitates the CO desorption on its surface, thereby improving the selectivity for CO production. High CO2 photoreduction and selectivity for CO production is demonstrated by the TMOF/CNNS-coated optical fiber with the cladding/core diameter of 2000/1000µm, 10 wt% TMOF in CNNS, coating thickness of 25µm, initial CO2 concentration of 90 vol%, and relative humidity of 88% RH under the excitation wavelength of 380-780nm. Overall, the photocatalytic hollow optical fiber developed herein provides an effective and efficient approach for the enhancement of light utilization efficiency of photocatalysts and selective CO2 reduction.