Heterointerface of all-alkynyl-protected Au_(28) nanoclusters anchored on NiFe-LDHs boosts oxygen evolution reaction:a case to unravel ligand effect

Ultrasmall Au nanoclusters have been proven to effectively enhance the catalytic performance of NiFe layered double hydroxides(NiFe-LDHs)toward oxygen evolution reaction(OER),yet the surface ligand effect of the Au nanoclusters still remains elusive.Herein,a systematic study is reported to examine the OER performance of NiFe-LDHs supported atom-precise all alkynyl-protected[Au_(28)(~tBuC≡C)17]~-nanoclusters(Au_(28)-Alkynyl in short)and thiolate-protected Au_(28)(TBBT)_(20)(TBBT=4-tert-butylbenzene thiol)counterp arts(Au_(28)-Thiolate in short).The Au_(28)-Alkynyl cluster has characteristic absorbance feature,and its composition is verified by mass spectrometry.It possesses a drastically different structure from the reported mixed ligand protected Au_(28)nanoclusters.Interestingly,the NiFe-LDHs loaded with Au_(28)-Alkynyl exhibited a superior OER performance than the sample loaded with Au28-Thiolate under the same conditions,evidenced by a smaller overpotential of 205 mV at the current density of 10 mA·cm^(-2)and a lower Tafel slope value of 41.0 mV·dec^(-1)in 1 mol·L^(-1)KOH.Such excellent performance is attributed to the interfaces created between the NiFe-LDHs and the Au nanoclusters,as density functional theory calculations reveal that more significant charge transfer occurs in Au_(28)-Alkynyl/NiFeLDHs catalyst,and more importantly,the energy barrier of the potential-determining step in the OER process for Au28-Alkynyl/NiFe-LDHs is much lower than that of Au28-Thiolate/NiFe-LDHs hence favors the electrocatalytic reaction.

Worldwide carbon neutrality transition?Energy efficiency,renewable,carbon trading and advanced energy policies

Climate change and energy shortage crisis promptly necessitate achievement of sustainable development goals.However,there is no straightforward pathways for low-carbon transformation on building sectors,and energy/carbon trading and reverse promotion on decarbonization strategies are not clear.In this study,a literature enumeration method with dialectical analysis was adopted for state-of-the-art literature review and comparison.Low-carbon transformation pathways in buildings were holistically reviewed,with a series of integrated techniques,such as energy saving,clean energy supply,flexible demand response for high self-consumption,and even smart electric vehicle(EV)integration.Afterwards,energy/carbon flows and trading in building-related systems were provided,such as peer-to-peer energy trading,building and thermal/power grids,building and energyintegrated EVs,and carbon trading in buildings.Last but not the least,worldwide decarbonization roadmaps across regions and countries are analysed,to identify the most critical aspects and immediate actions on decarbonization.Results indicate that tradeoff strategies are required to compromise the confliction between insufficient feed-in tariff(FiT)incentives(low renewable penetration in the market)and great economic pressures(high investment in renewable systems).Low-carbon building pathway is further enhanced with first priority given to passive/active energy-saving strategies,onsite clean energy supply and then flexible demand response.Energy/carbon trading will significantly affect renewable energy utilization,and acceptance from end-users to actively install renewable systems or participate in EV interactions.Worldwide decarbonization pathways mainly focus on industries,transportation,buildings,renewable sources,carbon sink and carbon capture,utilization and storage(CCUS).This study can contribute to technical roadmaps and strategies on carbon neutrality transition in both academia and industry,together with advanced policies in grid feed-in tariff,energy/carbon trading and business models worldwide.

General Synthetic Iterative Scheme for Unsteady Rarefied Gas Flows

In rarefied gas flows,the spatial grid size could vary by several orders of magnitude in a single flow configuration(e.g.,inside the Knudsen layer it is at the order of mean free path of gas molecules,while in the bulk region it is at a much larger hydrodynamic scale).Therefore,efficient implicit numerical method is urgently needed for time-dependent problems.However,the integro-differential nature of gas kinetic equations poses a grand challenge,as the gain part of the collision operator is non-invertible.Hence an iterative solver is required in each time step,which usually takes a lot of iterations in the(near)continuum flow regime where the Knudsen number is small;worse still,the solution does not asymptotically preserve the fluid dynamic limit when the spatial cell size is not refined enough.Based on the general synthetic iteration scheme for steady-state solution of the Boltzmann equation,we propose two numerical schemes to push the multiscale simulation of unsteady rarefied gas flows to a new boundary,that is,the numerical solution not only converges within dozens of iterations in each time step,but also asymptotically preserves the Navier-Stokes-Fourier limit in the continuum flow regime,when the spatial grid is coarse,and the time step is large(e.g.,in simulating the extreme slow decay of two-dimensional Taylor vortex,the time step is even at the order of vortex decay time).The properties of fast convergence and asymptotic preserving of the proposed schemes are not only rigorously proven by the Fourier stability analysis for simplified gas kinetic models,but also demonstrated by several numerical examples for the gas kinetic models and the Boltzmann equation.

An atmospheric water harvester with fast and energy-saving water removal and recovery

Moisture removal and water recovery from the air are vital for regulating indoor humidity and mitigating water scarcity.Most atmospheric water harvesters(AWH)focus primarily on increasing the moisture capture rate,but for it to be economical and sustainable,it is essential to consider the energy required to recover and harvest the captured water.Here,a mechanically flexible,biphilic sorption-based AWH made of green,environmentally friendly material is presented.It consists of a hygroscopic chitosan polymer embedded within a flexible,hydrophobic silica xerogel that can harvest 86.3 g water/g chitosan at 97%relative humidity and 25℃reaching saturation after 30 days(i.e.2.88 g water/g chitosan/day).Roughly 88%of the sorbed moisture was recovered by mechanical squeezing(ca.0.020 MPa)within 150 s.Repeated water harvesting experiments and uniaxial compression tests demonstrate that chitosan-silica xerogel is durable for longterm operations,providing a fast,reliable,and sustainable moisture removal and water harvesting tool.