‘Kapok fiber-PPy aerogels were prepared by using polypyrrole modification of the Ca2+ crosslinked kapok fiber aerogels. The kapok fiber-PPy aerogels show excellent light absorption, high porosity and mechanical strength’. As a solar steam generator a high energy conversion efficiency of 82.4% was obtained under 1 sun illumination.

No abstract

No abstract

No abstract

Solar-driven interfacial evaporation integrating inexhaustible solar energy and abundant seawater to address the scarcity of freshwater is a green and sustainable solution, but its industrial application remains challenging. Herein, a solar-utilizing device with a light-reflection layer was first proposed and fabricated for the improvement of light absorption as an efficient solar-driven interfacial salt-resistance evaporator, which consists of reduced graphene oxide-modified melamine sponge (rGOMS) (light-absorption layer) and aluminum foil (light-reflection layer). The strategy endows the assembled evaporator with high broadband light absorption (6.5% higher than that of the evaporator without a reflective layer), superior thermal insulation (0.0148 W m–1 K–1 in dry state), and continuous water transportation. Furthermore, the melamine sponge-based evaporator with a three-dimensional network structure (porosity of 99%) exhibits stable salt-resistance performance even in 20 wt % brine. As a result, the as-prepared evaporator (rGOMS-Re) has the merits of facile fabrication, durability, high cost-efficiency, and a stable photothermal evaporation efficiency of 87.5% under 1 kW m–2 illumination (12.2% higher than that of the evaporator without a reflective layer) and has promise to be an ideal candidate for scalable practical application. The strategy to improve light absorption opens a new and simple route for obtaining photothermal materials with light loss.

No abstract

Motivated by recent progress on field-induced phase transitions in quasi-one-dimensional quantum antiferromagnets, we study the phase diagram of S = 1/2 antiferromagnetic Heisenberg chains with Ising anisotropic interchain couplings under a longitudinal magnetic field via large-scale quantum Monte Carlo simulations. The interchain interactions is shown to enhance longitudinal spin correlations to stabilize an incommensurate longitudinal spin density wave order at low temperatures. With increasing field the ground state changes to a canted antiferromagnetic order until the magnetization fully saturates above a quantum critical point controlled by the (3 + 2)D XY universality. Increasing temperature in the quantum critical regime the system experiences a fascinating dimension crossover to a universal Tomonaga-Luttinger liquid. The calculated NMR relaxation rate 1/T1 indicates this Luttinger liquid behavior survives a broad field and temperature regime. Our results determine the global phase diagram and quantitative features of quantum criticality of a general model for quasi-onedimensional spin chain compounds, and thus lay down a concrete ground to the study on these materials. Introduction.In low-dimensional correlated electron systems strong quantum fluctuations give rise to quantum phase transitions (QPTs) [1] and a number of exotic quantum phenomena, such as unconventional superconductivity [2, 3], non-Fermi liquid behavior [4,5], and quantum spin liquids [6]. In the past decade, tremendous progresses have been made in understanding the nature of QPTs and associated emerging phenomena in quasi-one-dimensional (Q1D) antiferromagnets. These include the E 8 symmetry [7-9], manybody string excitations [10,11] and novel quantun criticality [12,13] in transverse field Ising chains, and Bose-Einstein condensation (BEC) and glassy phases in coupled antiferromagnetic (AFM) chains [14,15]. As a paradigmatic model for 1D quantum antiferromagnets, the S = 1/2 Heisenberg chain is well described by a Tomonaga-Luttinger liquid (TLL), where both the longitudinal and transverse spin correlation functions follow algebraic decay.[16] Under a magnetic field, the staggered transverse correlations are always dominant over the longitudinal ones, and a canted AFM order with staggered transverse correlations (denoted as the TAF order) is stabilized when interchain couplings become relevant. In systems with an Ising anisotropy, besides the TAF phase which arises from a spinflop mechanism [17], the peculiar quantum fluctuations in the Ising anisotropic XXZ chain give rise to incommensurate modulation of the longitudinal spin correlations [18] and can stabilize an incommensurate longitudinal spin density wave (LSDW) order [19]. This LSDW state has been recently observed in several Q1D antiferromagnets [20-22, 24, 25].Recent inelastic neutron scattering (INS) measurements reveal quantum critical TLL behavior of a coupled S = 1/2 chain compound YbAlO 3 with nearly isotropic (Heisenberg) intrachain exchange couplings [26]. A surprising obse...

The development of non-noble metal electrocatalysts with high-performance and low cost are promising to replace expensive Pt or Pt-based alloy electrocatalysts for the oxygen reduction reaction (ORR). Herein, we demonstrate the fabrication of N-rich metal-free electrocatalysts based on hard carbon nanotubes derived from carbonization of nanotube-like porphyrin-based conjugated microporous polymers (denoted as TPP-CMP) for ORR. Taking advantage of their high specific surface, excellent porosity, and importantly, exposed N–C active site originating from the N-doping carbon nanotubes with unique hollow cylindrical geometry, the as-synthesized TPP-CMP exhibits excellent catalytic activity for ORR in alkaline medium. It shows a half-wave potential of 0.83 V, an onset potential of 0.95 V (vs RHE), a high diffusion limiting current density of 4.6 mA cm–2, which is comparable to the commercial Pt/C catalyst. More importantly, the TPP-CMP manifests higher methanol immunity and long-term stability than that of commercial Pt/C (20 wt %) catalyst for ORR in an alkaline medium. Furthermore, TPP-CMP exhibits a favorable a 4-electron reduction of oxygen (n ≈ 3.95) and lower H2O2 yield. These results make the TPP-CMP promising candidate as efficient electrocatalysts for ORR. In view of the designable flexibility and synthetic diversity of porous organic polymers (POPs), the findings obtained from this study may also open new possibilities for the future tailored design of POPs for creation of high-performance, metal-free ORR electrocatalyst only by a simple calcination process.