Chemically modified electrodes formed by π-stacking of metalloporphyrins provide a stable and efficient electrocatalytic system for the hydrogen evolution reaction at pH 7.0. Metalloporphyrins M-OEP (M = Co(II), Cu(II), Zn(II), Ru(II), Fe(III) and Ni(II), OEP = 2,3,7,8,12,13,17,18-Octaethyl-21H,23H-porphine) were deposited on glassy carbon electrodes that had been previously modified by using NaOH and 4aminopyridine, which served as a bridging molecule between the metalloporphyrins and the electrode surface. Different supramolecular architectures, as revealed by AFM and SEM, were obtained with bare and oxidized glassy carbon electrode surfaces. The most active systems were those obtained with Co(II) and Cu(II) porphyrins. Raman spectra showed the presence of the linking molecules and metalloporphyrins in the electrocatalytic metalloporphyrin films.
Several factors affect photocatalytic hydrogen productivity from the photoreforming of organic compounds, which makes it difficult to optimize operational conditions in photoreactors. To prioritize these factors, we focused on the quantification of the effect of five of them on hydrogen production. Photocatalytic experiments were performed on 67 mL batch photoreactors under UV‐LED lamps (λ=375 nm) using a suspension of TiO2–Au nanoparticles synthesized by a sol–gel approach. The analyzed factors were: (A) presence of Au as a cocatalyst, (B) type of alcohol as the electron donor, (C) intensity of UV light, (D) electron donor concentration, and (E) nanoparticle concentration. A main and interaction effects analysis is presented with reduced fixed effect models for three responses: total hydrogen generation, catalyst productivity, and electron donor productivity. The presence of Au as a cocatalyst (A), the intensity of UV light (C), and their interaction (AC) were the factors with the highest effect. The best configuration allowed us to reach a catalyst productivity of 2925 μmolnormalH2
g−1 h−1.
Although advances have been made in combustion efficiency in large-scale woodchip furnaces, less experimental results are available at the <20 kW range. Compact feed systems, as well as optimized grates and combustor chambers, continue to represent a challenge for the wider use of low-cost wood chips. This study describes the design and testing of a small-scale woodchip furnace that operates at a range of 9-18 kW. The efficiency test takes account of the feedstock Eucalyptus nitens, with three moisture contents and the combination of different air excess (λ) and primary/secondary air ratios. The results reveal a maximum of combustion efficiency of 85% for the low moisture content sample (16%) at λ=1,5 and 82% for samples with 29% and 40% moisture content, at λ= 2,0 and 2,1 respectively. The integrated heat exchanger proved to be highly efficient by reducing gas temperature by up to 69% prior to its exit.
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