Jiaqi Yu

The world’s first demonstration of passive radiative cooling under the sun in 2014 attracted substantial attention due to its ubiquitous and passive nature. Numerous nanophotonic and metamaterials capable of radiative sky cooling have been reported over the past decade. However, the cooling power density of such materials is approximately one magnitude lower (100 W m-2) compared to terrestrial solar irradiation. Furthermore, improved optical characteristics could yield a modest increase in cooling power density due to the blackbody radiation limit. We report a rationally designed AsymSkyCool method (Asymmetrically-sized heat-source-on-radiative-Sky-Cooling-coated-substrate) for radiative sky cooling thermal concentration (tcRC). The tcRC concept yields over 2000 W m-2 at night and close to 1000 W m-2 at 493 W m-2 solar irradiation. The nearly tenfold improvement over the state-of-the-art sky cooling …

Hydrogenation of biomass‐derived chemicals is of interest for the production of biofuels and valorized chemicals. Thermochemical processes for biomass reduction typically employ hydrogen as the reductant at elevated temperatures and pressures. Here we investigate direct electrified reduction of 5‐Hydroxymethylfurfural (HMF) to a precursor to bio‐polymers, 2,5‐bis(hydroxymethyl)furan (BHMF). Noting a limited current density in prior reports of this transformation, we investigated the use of a hybrid catalyst consisting of ternary metal nanodendrites mixed with a cationic ionomer, the latter purposed to increase local pH and facilitate surface proton diffusion. We found that the approach, when implemented using Ga‐doped Ag‐Cu electrocatalysts designed for p‐d orbital hybridization, steered selectivity to BHMF, achieving a faradaic efficiency of 58% at 100 mA/cm2 and a production rate of 1 mmol/cm2/h, this latter …

Moisture-based adsorption thermal battery (ATB) holds great potential for addressing energy storage and utilization challenges. In this work, a proof-of-concept solar harvesting building envelope using the Trombe-wall (T-wall) based ATB design is proposed and investigated, featuring a developed composite sorbent as the porous wall for effective heat storage and utilization. To demonstrate the feasibility of employing the ATB-based building envelope for day-and-night space heating, a 3-dimensional simulation model of the ATB wall is meticulously designed and comprehensively studied. Parametric analyses of various working conditions, including examining the effects of solar radiation intensity, air temperature, air humidity, and airflow velocity on the heat charging and discharging performances of the ATB wall, are conducted using the numerical model. Simulation results indicate that, under a solar irradiance …

Perovskite solar cells have seen impressive progress in performance and stability, yet maintaining efficiency while scaling area remains a challenge. Here we find that additives commonly used to passivate large-area perovskite films often co-precipitate during perovskite crystallization and aggregate at interfaces, contributing to defects and to spatial inhomogeneity. We develop design criteria for additives to prevent their evaporative precipitation and enable uniform passivation of defects. We explored liquid crystals with melting point below the perovskite processing temperature, functionalization for defect passivation and hydrophobicity to improve device stability. We find that thermotropic liquid crystals such as 3,4,5-trifluoro-4′-(trans-4-propylcyclohexyl)biphenyl enable large-area perovskite films that are uniform, low in defects and stable against environmental stress factors. We demonstrate modules with a …

Ethylene oxide (EO) is one of the most crucial materials in plastic industries. The traditional catalytic process requires high temperature and pressure to produce EO. A chlorine-assisted system has been reported to produce EO, but it required noble metal catalysts, which significantly increased the cost. In this work, a MOF-derived Co3O4/nitrogen-doped carbon composite (Co3O4/NC) prepared through a two-step calcination method exhibited remarkable chlorine evolution reaction (ClER) activity as compared with a commercial RuO2 catalyst, which can be attributed to the higher specific surface area and lower resistance of its porous structure and nitrogen-doped carbon. Furthermore, the Co3O4/NC maintained a stable potential and a high faradaic efficiency throughout the 10-hour electrolysis test.

Catalytic hydrogenolysis of polyolefins into valuable liquid, oil, or wax-like hydrocarbon chains for second-life applications is typically accompanied by the hydrogen-wasting co-formation of low value volatiles, notably methane, that increase greenhouse gas emissions. Catalytic sites confined at the bottom of mesoporous wells, under conditions in which the pore exerts the greatest influence over the mechanism, are capable of producing less gases than unconfined sites. A new architecture was designed to emphasize this pore effect, with the active platinum nanoparticles embedded between linear, hexagonal mesoporous silica and gyroidal cubic MCM-48 silica (mSiO2/Pt/MCM-48). This catalyst deconstructs polyolefins selectively into ∼C20–C40 paraffins and cleaves C–C bonds at a rate (TOF = 4.2 ± 0.3 s–1) exceeding that of materials lacking these combined features while generating negligible volatile side …

Thermal management is becoming the main bottleneck of electronic devices, especially in situations where only passive strategies are available, such as base stations and smartphones. In this article, we develop passive, sorption-based evaporative cooling based on a salt-embedded composite sorbent and further apply the method to a state-of-the-art 5G base station. Both the experimental and simulation results demonstrate that the proof of concept on a finned heat sink could achieve an exceptional equivalent cooling power of 602 W/m2, which accounts for about 22% of the total heat dissipation capacity and could bring a maximum of 20°C temperature reduction compared with the original device. An additional experiment on a well-developed practical base station demonstrates that the proposed cooling strategy could still bring about a 5°C–8°C temperature reduction. Sorption-based evaporative cooling could …

Pretreatment conditions dramatically alter the active surface of catalytic materials, influencing their performance. In a recent study, Monai et al. investigated the structural evolution of nickel nanoparticles (Ni NPs) supported on the reducible oxide TiO2 during the CO2 hydrogenation reaction. Operando electron microscopy showed the formation of TiOx bilayers during reductive pretreatments at 400°C, while thicker TiOx overlayers were generated during more aggressive pretreatment at 600°C. Under CO2 hydrogenation conditions, the TiOx bilayers receded, but small TiOx domains remained on the Ni/TiO2 materials that underwent pretreatment at 600°C. The partially intact TiOx overlayer led to an extensive interface between Ni and TiOx, improving catalytic activity and selectivity toward C2+ products that are particularly desired in CO2 utilization schemes.

Balancing kinetics, a crucial priority in catalysis, is frequently achieved by sacrificing activity of elementary steps to suppress side reactions and enhance catalyst stability. Dry reforming of methane (DRM), a process operated at high temperature, usually involves fast C-H activation but sluggish carbon removal, resulting in coke deposition and catalyst deactivation. Studies focused solely on catalyst innovation are insufficient in addressing coke formation efficiently. Herein, we develop coke-free catalysts that balance kinetics of elementary steps for overall thermodynamics optimization. Beginning from a highly active cobalt aluminum oxide (CoAl2O4) catalyst that is susceptible to severe coke formation, we substitute aluminum (Al) with gallium (Ga), reporting a CoAl0.5Ga1.5O4-R catalyst that performs DRM stably over 1000 hours without observable coke deposition. We find that Ga enhances DRM stability by …

Heterostructured nanomaterials are of interest for many applications due to their unique properties, which depend on the identity of each individual component and the interface between them. However, the difficulty of controlling the synthesis of heterostructures and the interfaces between components limits their applications. Here we develop a colloidal synthetic method to prepare heterostructured intermetallic nanomaterials (iNMs) and engineer the interfaces between the individual components, based on the galvanic replacement mechanism and precisely controlled addition of precursors. Up to four distinct intermetallic phase-segregated segments could be combined in one nanoparticle. Nanometre-precision phase-segregated control along one dimension of iNMs was demonstrated by taking advantage of the layered growth pathway at the intermetallic–metal interfaces, leading to a maximum number of …

Industrial water splitting pairs cathodic hydrogen evolution with oxygen evolution at the anode, the latter generating low-value oxygen as the oxidative product. We reasoned that replacing the oxygen evolution reaction (OER) with anodic electrosynthesis of acetic acid from ethanol at industrial current densities could be a route to increase the economic efficiency of green hydrogen production. We partition the selective oxidation of ethanol to acetic acid into two mechanistically distinct transformations: first ethanol oxidation followed by the production of *OH. Density functional theory (DFT) studies show that the aldehyde-derived intermediate CH3CO* from ethanol oxidation and the *OH radical from water dissociation are both needed in the electroproduction of acetic acid. Operando Fourier transform infrared (FTIR) spectroscopy identifies the corresponding aldehyde intermediates on the anode surface. Based on …

Electrocatalytic oxidative dehydrogenation (EOD) of aldehydes enables ultra-low voltage, bipolar H2 production with co-generation of carboxylic acid. Herein, we reported a simple galvanic replacement method to prepare CuM (M = Pt, Pd, Au, and Ag) bimetallic catalysts to improve the EOD of furfural to reach industrially relevant current densities. The redox potential difference between Cu/Cu2+ and a noble metal M/My+ can incorporate the noble metal on the Cu surface and enlarge its surface area. Particularly, dispersing Pt in Cu (CuPt) achieved a record-high current density of 498 mA cm–2 for bipolar H2 production at a low cell voltage of 0.6 V and a Faradaic efficiency of >80% to H2. Future research is needed to deeply understand the synergistic effects of Cu–M toward EOD of furfural, and improve the Cu–M catalyst stability, thus offering great opportunities for future distributed manufacturing of green hydrogen …

Temperature control of electronic devices is becoming increasingly important. A better temperature control strategy could improve system performance without any change in the hardware-based thermal design. However, the development of temperature control algorithms is still challenging due to the multiple inner heat sources and thermal constraints, which causes a widespread use of the basic look-up table method on current devices. In this paper, the control performance of model predictive control (MPC) on a laptop is numerically evaluated based on the MATLAB/FLUENT co-simulation framework. In the MPC algorithm, a skin temperature reconstruction model is contained to online estimate the temperature of exterior surfaces based on the information of inner sensors, and a simplified temperature prediction model is utilized to predict the future temperature of both the exterior surfaces and inner sensors. The …

Boron monoxide (BO), prepared by the thermal condensation of tetrahydroxydiboron, was first reported in 1955; however, its structure could not be determined. With the recent attention on boron-based two-dimensional materials, such as borophene and hexagonal boron nitride, there is renewed interest in BO. A large number of stable BO structures have been computationally identified, but none are supported by experiments. The consensus is that the material likely forms a boroxine-based two-dimensional material. Herein, we apply advanced 11B NMR experiments to determine the relative orientations of B(B)O2 centers in BO. We find that the material is composed of D2h-symmetric O2B–BO2 units that organize to form larger B4O2 rings. Further, powder diffraction experiments additionally reveal that these units organize to form two-dimensional layers with a random stacking pattern. This observation is in …

In most portable electronic devices, besides the temperature of multiple heat sources, i.e. junction temperature, the temperature of the enclosure, i.e. skin temperature, should also be controlled to protect the user experience. Thus, generating the device-level compact thermal model for predicting the skin temperature will not only improve the efficiency of early-stage thermal design but also help to develop the model-based temperature control strategy. However, most of the existing modeling methods mainly focus on predicting the junction temperature. In this paper, the dynamic compact thermal models of two portable electronic devices, including a smartphone and laptop, are first generated based on the convolution method. Under the assumption of linear time-invariant (LTI) systems, the skin temperature of the two test devices could be fast calculated once the step response of each heat source is obtained. The …

The electrochemical carbon dioxide reduction reaction (CO2RR) is a transformative technology to reduce the carbon footprint of modern society. Single‐site catalysts have been demonstrated as promising catalysts for CO2RR, but general synthetic methods for catalysts with high surface area and tunable single‐site metal composition still need to be developed to unambiguously investigate the structure–activity relationship crossing various metal sites. Here, a generalized coordination–condensation strategy is reported to prepare single‐atom metal sites on ordered mesoporous carbon (OMC) with high surface areas (average 800 m2 g‐1). This method is applicable to a broad range of metal sites (Fe, Co, Ni, Cu, Pt, Pd, Ru, and Rh) with loadings up to 4 wt.%. In particular, the CO2RR to carbon monoxide (CO) Faradaic efficiency (FE) with Ni single‐site OMC catalyst reaches 95%. This high FE is maintained even …

Solid-state nuclear magnetic resonance can be enhanced using unpaired electron spins with a method known as dynamic nuclear polarization (DNP). Fundamentally, DNP involves ensembles of thousands of spins, a scale that is difficult to match computationally. This scale prevents us from gaining a complete understanding of the spin dynamics and applying simulations to design sample formulations. We recently developed an ab initio model capable of calculating DNP enhancements in systems of up to∼ 1000 nuclei; however, this scale is insufficient to accurately simulate the dependence of DNP enhancements on radical concentration or magic angle spinning (MAS) frequency. We build on this work by using ab initio simulations to train a hybrid model that makes use of a rate matrix to treat nuclear spin diffusion. We show that this model can reproduce the MAS rate and concentration dependence of DNP …

Developing non-precious metal catalysts to selectively reduce functionalized nitroarenes with high efficiency is urgently desirable for the production of value-added amines. Herein, we report a novel, efficient, anti-poisoning single-atom cobalt catalyst (Co-NAC) for the highly selective hydrogenation of the nitro to amino group for nitroarenes baring various functional groups, including vinyl, cyano, and halogen. Using a combination of structure characterization techniques, we have confirmed that the cobalt species are predominantly present in the form of four-coordinated Co single sites anchored on nitrogen-assembly carbon (NAC) as the ordered mesoporous support. Co-NAC catalysts enable the full conversion and > 99% selectivity with molecular H2 as a green reductant under mild conditions (80 °C, 2 MPa H2). As for the selective hydrogenation of 3-nitrostyrene, Co-NAC catalyst affords high catalytic productivity …

dc. description. abstract With the rapid growth of heterogeneous catalysis, designing and preparing catalysts to fulfill new catalytic reaction requirements becomes essential. Nanomaterials and single-atom catalysts attract significant attention due to their high atom utilization efficiency. Intermetallic nanomaterials, a subcategory of alloy with defined stoichiometry and ordered crystal structure, bring opportunity to heterogeneous catalysis because of their enhanced catalytic activity, selectivity, and stability. In this dissertation, a galvanic replacement-based colloidal synthesis method was developed to construct an intermetallic nanomaterial library consisting of intermetallic nanomaterials with both single component and structural complexity. The synthesized intermetallic nanomaterials were applied to electrocatalytic nitrate and furfural reduction reactions. In addition to developing a new synthesis approach, a general …

A hybrid catalyst with integrated single-atom Ni and nanoscale Cu catalytic components is reported to enhance the C–C coupling and ethylene (C2H4) production efficiency in the electrocatalytic CO2 reduction reaction (eCO2RR). The single-atom Ni anchored on high-surface-area ordered mesoporous carbon enables high-rate and selective conversion of CO2 to CO in a wide potential range, which complements the subsequent CO enrichment on Cu nanowires (NWs) for the C–C coupling to C2H4. In situ surface-enhanced infrared absorption spectroscopy (SEIRAS) confirms the substantially improved CO enrichment on Cu, once the incorporation of single-atom Ni occurs. Also, in situ X-ray absorption near-edge structure (XANES) demonstrates the structural stability of the hybrid catalyst during eCO2RR. By modulating hybrid compositions, the optimized catalyst shows 66% Faradaic efficiency (FE) in an alkaline …