Ag nanoparticles anchored organic/inorganic Z‐scheme 3DOMM‐TiO_(2‒x)‐based heterojunction for efficient photocatalytic and photoelectrochemical water splitting

Narrow spectral response,low charge separation efficiency and slow water oxidation kinetics of TiO_(2)limit its application in photoelectrochemical and photocatalytic water splitting.Herein,a promising organic/inorganic composite catalyst Ag/PANI/3DOMM‐TiO_(2–x)with a three‐dimensional ordered macro‐and meso‐porous(3DO MM)structure,oxygen vacancy and Ti^(3+)defects,heterojunction formation and noble metal Ag was designed based on the Z‐scheme mechanism and successfully prepared.The Ag/PANI/3DOMM‐TiO_(2–x)ternary catalyst exhibited enhanced hydrogen production activity in both photocatalytic and photoelectrochemical water splitting.The photocatalytic hydrogen production rate is 420.90μmol g^(–1)h^(–1),which are 19.80 times and 2.06 times higher than the commercial P25 and 3DOMM‐TiO_(2),respectively.In the photoelectrochemical tests,the Ag/PANI/3DOMM‐TiO_(2–x)photoelectrode shows enhanced separation and transfer of carriers with a high current density of 1.55 mA cm^(–2)at equilibrium potential of 1.23 V under simulated AM 1.5 G illumination,which is approximately 5 times greater than the 3DOMM‐TiO_(2).The present work has demonstrated the promising potential of organic/inorganic Z‐scheme photocatalyst in driving water splitting for hydrogen production.

An Experimental Study of the Performance of Isomorphically Zirconium-Substituted Mesoporous Alumina Supported Cobalt Catalysts in Fischer-Tropsch Synthesis

A series of mesoporous alumina (MA) supported cobalt (Co/MA) catalysts with MA isomorphically substituted by zirconium (Zr) were synthesised and evaluated for their performance in the Fischer-Tropsch synthesis. The Zr/(Zr + Al) atomic ratios varied from 1% - 15%. A zirconium-impregnated Co/MA catalyst prepared by wet impregnation with a Zr/(Zr + Al) atomic ratio of 5% was also evaluated to examine Zr incorporation’s effect method. The catalysts synthesised were characterised using N2 adsorption-desorption, X-ray Powder Diffraction (XRD), Transmission Electron Microscopy (TEM), and X-Ray Photoelectron Spectroscopy (XPS). It was found that Zr4+ ions were incorporated into the framework of MA and kept intact up to a Zr/(Zr + Al) atomic ratio of 5%. The cobalt dispersion and reducibility were improved as the Zr/(Zr + Al) atomic ratio increased to 50%. The performance of these catalysts for Fischer-Tropsch synthesis was evaluated using a fixed bed reactor at temperature and pressure of 493 K and 20 bar, respectively. The feed syngas had an H2/CO ratio of 2, diluted with 10% Ar. For isomorphically Zr-substituted Co/MA, the CO conversion and selectivity of diesel (C10 - C20) increased first and then decreased with increasing the Zr/(Zr + Al) atomic ratio. The maximum 38.9% CO conversion and 34.6% diesel (C10 - C20) selectivity were obtained at Zr/(Zr + Al) atomic ratio of 5%. The isomorphic substitution method was better than the wet impregnation method in CO conversion and diesel selectivity.

Process reconfiguration and intensification:An emerging opportunity enabling efficient carbon capture and low-cost blue hydrogen production

Low-carbon hydrogen can play a significant role in decarbonizing the world. Hydrogen is currently mainly produced from fossil sources,requiring additional CO_(2)capture to decarbonize, which energy intense and costly. In a recent Green Energy & Environment paper, Cheng and Di et al. proposed a novel integration process referred to as SECLR_(HC) to generate high-purity H_(2) by in-situ separation of H_(2)and CO without using any additional separation unit. Theoretically, the proposed process can essentially achieve the separation of C and H in gaseous fuel via a reconfigured reaction process, and thus attaining high-purity hydrogen of ~99%, as well as good carbon and hydrogen utilization rates and economic feasibility. It displays an optimistic prospect that industrial decarbonization is not necessarily expensive, as long as a suitable CCS measure can be integrated into the industrial manufacturing process.

An Experimental Observation of the Thermal Effects and NO Emissions during Dissociation and Oxidation of Ammonia in the Presence of a Bundle of Thermocouples in a Vertical Flow Reactor

Ammonia (NH3) dissociation and oxidation in a cylindrical quartz reactor has been experimentally studied for various inlet NH3 concentrations (5%, 10%, and 15%) and reactor temperatures between 700 K and 1000 K. The thermal effects during both NH3 dissociation (endothermic) and oxidation (exothermic) were observed using a bundle of thermocouples positioned along the central axis of the quartz reactor, while the corresponding NH3 conversions and nitrogen oxides emissions were determined by analysing the gas composition of the reactor exit stream. A stronger endothermic effect, as indicated by a greater temperature drop during NH3 dissociation, was observed as the NH3 feed concentration and reactor temperature increased. During NH3 oxidation, a predominantly greater exothermic effect with increasing NH3 feed concentration and reactor temperature was also evident;however, it was apparent that NH3 dissociation occurred near the reactor inlet, preceding the downstream NH3 and H2 oxidation. For both NH3 dissociation and oxidation, NH3 conversion increased with increasing temperature and decreasing initial NH3 concentration. Significant levels of NOX emissions were observed during NH3 oxidation, which increased with increasing temperature. From the experimental results, it is speculated that the stainless-steel in the thermocouple bundle may have catalysed NH3 dissociation and thus changed the reaction chemistry during NH3 oxidation.

固定床中甲烷在不同煤焦上的裂解制氢

本文以煤焦与甲烷共转化为背景,采用小型石英管固定床反应装置,于在1123 K下对甲烷在褐煤焦、脱灰煤焦、活化煤焦以及石英砂床层上的裂解反应进行了较为详细的研究,并采用扫描电子显微镜以及比表面积测定仪对反应前后的褐煤焦、脱灰煤焦进行了表征。甲烷在脱灰煤焦和褐煤焦上的转化率相差不多,说明煤焦中的灰成分对甲烷裂解没有影响。在活化煤焦上,甲烷的转化率有了很大幅度的提高,最高可达97%左右。在脱灰煤焦活化过程中,煤焦活化程度越小越有利于甲烷的裂解,甲烷转化率最高可达97%左右,表明煤焦中的微晶对反应有影响。随着反应时间的增加,甲烷转化率以及氢气的收率逐渐降低,其主要原因是反应过程中甲烷裂解产生的积碳覆盖在煤焦表面上,使其催化活性降低。

More from less:improving solar steam generation by selectively removing a portion of evaporation surface

Using minimal photothermal material to achieve maximum evaporation rate is extremely important for practical applications of interfacial solar evaporation technology.In this work,we found that with the increase in the size of evaporation surfaces,the evaporation rate decreased.Both experimental and numerical simulation results confirmed that when the evaporation surface size increased,the middle portion of the evaporation surface acted as a‘‘dead evaporation zone”with little contribution to water evaporation.Based on this,the middle portion of the evaporation surface was selectively removed,and counterintuitively,both the evaporation rate and vapor output were increased due to the reconfigured and enhanced convection above the entire evaporation surface.As such,this work developed an important strategy to achieve a higher evaporation rate and increased vapour output while using less material.

Effect of oil shale semi-coke on deposit mineralogy and morphology in the flue path of a CFB burning Zhundong lignite

The effect of oil shale semi-coke(SC)on the mineralogy and morphology of the ash deposited on probes situated in the flue path of a circulating fluidized bed(CFB)which burns Zhundong lignite(ZD)was investigated.10 wt%or 20 wt%SC was added to ZD,which were then combusted in the CFB furnace at 950℃.Two probes with vertical and horizontal orientations were installed in the flue duct to simulate ash deposition.Both windward and leeward ash deposits on probes(P_(1)W,P_(1)L,P_(2)W and P_(2)L)were analyzed by using a scanning electron microscopy with energy dispersive X-ray(SEM-EDX),X-ray diffraction(XRD),an inductively coupled plasma optical emission spectrometry ICP-OES,and a particle size analyzer.When ZD was burned alone,the P1W deposit was comprised of agglomerates(<30µm)enriched in CaSO_(4)and Na_(2)SiO_(3),incurring significant sintering.The P1L and P2W deposits,however,were of both discrete and agglomerated particles in similar mineral phases but with coarser sizes.The P_(2)L deposit was mainly fine ash particles where Na_(2)SiO_(3)and Na_(2)SO_(4)were absent.As SC was added,the agglomerates in both P1W and P1L decreased.Moreover,SiO_(2)and Ca/Na aluminosilicates dominated the mineral phases whereas Na_(2)SiO_(3)and Na_(2)SO_(4)disappeared,showing a decrease in deposit stickiness.Likewise,the P2W deposit was found less spread on the probe,decreasing its deposition propensity.Na-bearing minerals turned into(Na,K)(Si_(3)Al)O_(8)and(Ca,Na)(Si,Al)4O8 in the P_(2)W deposit.Moreover,Na in the deposits decreased from 32 mg/g to less than 15 mg/g as SC presented.The addition of SC would therefore help alleviate the propensity of ash deposition in the flue path in the CFB combustion of ZD.