The photo-decomposition and self-restructuring dynamic equilibrium mechanism of Cu_(2)(OH)_(2)CO_(3)for stable photocatalytic CO_(2)reduction

Developing suitable photocatalysts and understanding their intrinsic catalytic mechanism remain key challenges in the pursuit of highly active,good selective,and long-term stable photocatalytic CO_(2)reduction(PCO_(2)R)systems.Herein,monoclinic Cu_(2)(OH)_(2)CO_(3)is firstly proven to be a new class of photocatalyst,which has excellent catalytic stability and selectivity for PCO_(2)R in the absence of any sacrificial agent and cocatalysts.Based on a Cu_(2)(OH)_(2)^(13)CO_(3)photocatalyst and 13CO_(2)two-sided^(13)C isotopic tracer strategy,and combined with in situ diffused reflectance infrared Fourier transform spectroscopy(DRIFTS)analysis and density functional theory(DFT)calculations,two main CO_(2)transformation routes,and the photo-decomposition and self-restructuring dynamic equilibrium mechanism of Cu_(2)(OH)_(2)CO_(3)are definitely revealed.The PCO_(2)R activity of Cu_(2)(OH)_(2)CO_(3)is comparable to some of state-of-the-art novel photocatalysts.Significantly,the PCO_(2)R properties can be further greatly enhanced by simply combining Cu_(2)(OH)_(2)CO_(3)with typical TiO_(2)to construct composites photocatalyst.The highest CO_(2)and CH_(4)production rates by 7.5 wt%Cu_(2)(OH)_(2)CO_(3)-TiO_(2)reach 16.4μmol g^(-1)h^(-1)and 116.0μmol g^(-1)h^(-1),respectively,which are even higher than that of some of PCO_(2)R systems containing sacrificial agents or precious metals modified photocatalysts.This work provides a better understanding for the PCO_(2)R mechanism at the atomic levels,and also indicates that basic carbonate photocatalysts have broad application potential in the future.

Lignin derived multi-doped(N, S, Cl) carbon materials as excellent electrocatalyst for oxygen reduction reaction in proton exchange membrane fuel cells

Nowadays,hierarchically macro-/meso-/microporous 3D carbon materials have been paid more attention due to their imaginative application potential in specific electrochemistry.Here,we report a dualtemplate strategy using eutectic NaCl/ZnCl2 melt as airtight and swelling agent to obtain 3D mesoporous skeleton structured carbon from renewable lignin.The prepared lignin-derived biocarbon material(LN-3-1)has a high specific surface area(1289 m^2 g^-1),a large pore volume(2.80 cm^3 g^-1),and a well-connected and stable structure.LN-3-1 exhibits extremely high activity and stability in acidic medium for oxygen reduction reaction(ORR),superior to Pt/C catalyst and most non noble-metal catalysts reported in recent literatures.The prepared carbon material was used as a cathode catalyst to assemble a H2-O2 single fuel cell,and its excellent catalytic performance has been confirmed with the maximum power density of 779 mW cm^-2,which is one of the highest power densities among non-metallic catalysts so far.Density functional theory(DFT)calculations indicate that the synergy of chlorine and nitrogen reconciles the intermediate adsorption energies,leading to an appropriate theoretical ORR onset potential.We develop a cost-effective and highly efficient method to prepare biocarbon catalyst for ORR in proton-exchange membrane fuel cells.

Noble-metal-based high-entropy-alloy nanoparticles for electrocatalysis

Since the two seminal papers were published independently in 2004, high-entropy-alloys(HEAs) have been applied to structural and functional materials due to the enhanced mechanical properties, thermal stability, and electrical conductivity. In recent years, HEA nanoparticles(HEA-NPs) were paid much attention to in the field of catalysis for the promoted catalytic activity. Furthermore, the various ratios among the metal components and tunable bulk and surface structures enable HEAs have big room to enhance the catalytic performance. Especially, noble-metal-based HEAs displayed significantly improved performance in electrocatalysis, where the ‘core effects’ were employed to explain the superior catalytic activity. However, it is insufficient to understand the essential mechanism or further guide the design of electrocatalysts. Structure–property relationship should be disclosed for the catalysis on HEA-NPs to accelerate the process of seeking high effective and efficient electrocatalysts. Therefore, we summarized the recent advances of noble-metal-based HEA-NPs applied to electrocatalysis, such as hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, methanol oxidation reaction, ethanol oxidation reaction, formic acid oxidation reaction, hydrogen oxidation reaction, carbon dioxide reduction reaction and nitrogen reduction reaction. For each electrocatalytic reaction, the reaction mechanism and catalyst structure were presented, and then the structure–property relationship was elaborated. The review begins with the development, concept, four ‘core effect’ and synthesis methods of HEAs. Next,the electrocatalytic reactions on noble-metal-based HEA-NPs are summarized and discussed independently. Lastly, the main views and difficulties pertaining to structure–property relationship for HEAs are discussed.

Syngas production by dry reforming of the mixture of glycerol and ethanol with CaCO3

The reduction of CO2 emission is crucial for the mitigation of climate change.A considerable amount of industrial CO2 can be absorbed in the form of carbonates through high-temperature sorption processes.In this regard,the efficient conversion of carbonates to value-added products will provide an economically viable method for the sustainable usage of carbon compounds.Herein,we report a promising solution involving the use of a glycerol and ethanol mixture as a hydrogen donor in the dry reforming process with CaCO3 to produce syngas.A series of metal active components,including Ni,Fe,Co,Cu,Pt,Pd,Ru,and Rh,was used to promote this reaction.Ni showed comparable performance with that of Pd,but outperformed Co,Fe,Cu,Rh,Ru,and Pt.Approximately 100%conversion of glycerol and ethanol,~92%selectivity of synthesis gas(H2 and CO),and a H2/CO ratio of^1.2 were achieved over CaCO3 containing10 wt%Ni(10Ni-CaCO3).Meanwhile,the CO2 concentration was less than 5 vol%,indicating that most of the CO2 captured by the carbonate can be transformed into chemicals;however,they cannot simply be emitted.The CO2 released from the decomposition of CaCO3 not only adjusted the ratio of H2 to CO but also eliminated cokes to guarantee the CO2 absorption-conversion cyclic stability in the absence of steam and at high temperatures.

Hydrogen production via autothermal reforming of ethanol over noble metal catalysts supported on oxides

Hydrogen was produced over noble metal（Ir, Ru, Rh, Pd） catalysts supported on various oxides, including γ-Al2O3, CeO2, ZrO2 and La2O3, via the autothermal reforming reaction of ethanol （ATRE） and oxidative reforming reaction of ethanol （OSRE）. The conversion of ethanol and selectivites for hydrogen and byproducts such as methane, ethylene and acetaldehyde were studied. It was found that lanthana alone possessed considerable activity for the ATRE reaction, which could be used as a functional support for ATRE catalysts. It was demonstrated that Ir/La2O3 prevented the formation of methane, and Rh/La2O3 encumbered the production of ethylene and acetaldehyde. ATRE reaction was carried out over La2O3-supported catalysts （Ir/La2O3） with good stability on stream, high conversion, and excellent hydrogen selectivity approaching thermodynamic limit under autothermal condition. Typically, 3.4H2 molecules can be extracted from a pair of ethanol and water molecules over Ir（5wt%）/La2O3. The results presented in this paper indicate that Ir/La2O3 can be used as a promising catalyst for hydrogen production via ATRE reaction from renewable ethanol.

Production of high-purity hydrogen from paper recycling black liquor via sorption enhanced steam reforming

Environmentally friendly and energy saving treatment of black liquor(BL),a massively produced waste in Kraft papermaking process,still remains a big challenge.Here,by adopting a NieCaOeCa_(12)Al_(14)O_(33) bifunctional catalyst derived from hydrotalcite-like materials,we demonstrate the feasibility of producing high-purity H_(2)(~96%)with 0.9 mol H_(2) mol^(-1) C yield via the sorption enhanced steam reforming(SESR)of BL.The SESRBL performance in terms of H_(2) production maintained stable for 5 cycles,but declined from the 6th cycle.XRD,Raman spectroscopy,elemental analysis and energy dispersive techniques were employed to rationalize the deactivation of the catalyst.It was revealed that gradual sintering and agglomeration of Ni and CaO and associated coking played important roles in catalyst deactivation and performance degradation of SESRBL,while deposition of Na and K from the BL might also be responsible for the declined performance.On the other hand,it was demonstrated that the SESRBL process could effectively reduce the emission of sulfur species by storing it as CaSO_(3).Our results highlight a promising alternative for BL treatment and H_(2) production,thereby being beneficial for pollution control and environment governance in the context of mitigation of climate change.

Taxonomic and functional variations in the microbial community during the upgrade process of a full-scale landfill leachate treatment plant-from conventional to partial nitrification-denitrification

Because of the low access to biodegradable organic substances used for denitrification,the partial nitrification-denitrification process has been considered as a low-cost,sustainable alternative for landfill leachate treatment.In this study,the process upgrade from conventional to partial nitrificationdenitrification was comprehensively investigated in a full-scale landfill leachate treatment plant(LLTP).The partial nitrification-denitrification system was successfully achieved through the optimizing dissolved oxygen and the external carbon source,with effluent nitrogen concentrations lower than 150 mg/L.Moreover,the upgrading process facilitated the enrichment of Nitrosomonas(abundance increased from 0.4%to 3.3%),which was also evidenced by increased abundance of amoA/B/C genes carried by Nitrosomonas.Although Nitrospira(accounting for 0.1%-0.6%)was found to stably exist in the reactor tank,considerable nitrite accumulation occurred in the reactor(reaching 98.8 mg/L),indicating high-efficiency of the partial nitrification process.Moreover,the abundance of Thauera,the dominant denitrifying bacteria responsible for nitrite reduction,gradually increased from 0.60%to 5.52%during the upgrade process.This process caused great changes in the microbial community,inducing continuous succession of heterotrophic bacteria accompanied by enhanced metabolic potentials toward organic substances.The results obtained in this study advanced our understanding of the operation of a partial nitrification-denitrification system and provided a technical case for the upgrade of currently existing full-scale LLTPs.

Bi-functional particles for integrated thermo-chemical processes:Catalysis and beyond

Particulate materials possessing dual functionalities have received tremendous investigations in many fields,owing to their superiority over mono-functional counterparts and their potential for process integration and intensification.This review focuses on bi-functional catalytic particles which also serve as sorbents/adsorbents or heat suppliers in the scheme of various thermo-chemical processes,enabling inherent separation or energy conservation within single-step operation.Bi-functional particles applied for integration of reaction and separation including sorption-enhanced hydrogen production and integrated capture and catalytic conversion processes are reviewed in detail,providing insights into material design and key performance indicators.On the other hand,bi-functional particles applied for integration of reaction and non-thermal radiation heating,including electrothermal and photothermal assisted heterogeneously catalyzed reactions,are also reviewed,with emphasis on the material property and energy efficiency improvement.These bi-functional particles show broad adaptability and feasibility in various reactions operated in integrated and intensified schemes,affording huge potentials for further improving productivity and efficiency in thermo-chemical processes.

Platinum-based ternary catalysts for the electrooxidation of ethanol

Direct ethanol fuel cell(DEFC)as a promising device for converting chemical energy to electricity has been paid ever-increasing attention.However,the slow kinetics of ethanol electrooxidation at an anode hinders the application of DEFCs.Although Pt is the best catalyst among all the pure metal catalysts,it still has a relatively poor ability to break the Csingle bondC bond,is deactivated by the accumulated CO_(ad) intermediates,and undergoes unwanted desired structure change over long-term operation.In recent years,the addition of other metals to form binary,ternary,and quaternary catalysts have significantly improved electroactivity and stability.Ternary catalysts can have numerous element combinations and complicated architectures and,therefore,have been the subject of considerable research.In this review,most of the reported ternary catalysts will be summarized and categorized according to their structure while discussing the essence of the role of each component.