Three Highly Stable Cobalt MOFs Based on "Y"-Shaped Carboxylic Acid: Synthesis and Absorption of Anionic Dyes.

Three Co(II) metal-organic frameworks (MOFs) were synthesized employing a rational design approach. On the basis of the different structures of three complexes, we tested their absorption properties toward two anionic dyes. The absorption results indicate that not only uncoordinated functional groups in the structure play an important role in adsorbing capacity but also physical forces can affect absorbing ability. Water stability testing shows that three crystals display high stability in aqueous solutions with different pH values. To our delight, the framework integrity of three complexes can be well-retained even after absorbing dyes.

FeNi-LDH COATED WITH ORANGE-PEEL CARBON AEROGEL FOR OXYGEN EVOLUTION REACTION.

In this work, the waste orange-peel was used as carbon source, and the orange-peel derived carbon material can be obtained through simple pyrolysis. Then, we designed the structure of orange-peel carbon aerogel grown on iron-nickel layered double hydroxides in situ to achieve the effect of carbon coating (FeNi-LDH/CA). The oxygen evolution reaction catalytic performance of FeNi-LDH/CA is excellent, far exceeding that of commercial RuO2. In 1 M KOH, the overpotential of FeNi-LDH/CA is only 250 mV (10 mA cm-2), obviously better than that of commercial RuO2 (295 mV). FeNi-LDH/CA shows good cycling stability, and after long-term i-t testing, the performance only decays by 3% after running at 100 mA cm-2 for 100 h. When used as an anode, the voltage of water-splitting is only 1.48 V at 10 mA cm-2. The rechargeable liquid zinc-air battery based on Pt/C-FeNi-LDH/CA catalyst has higher open-circuit voltage (1.543 V) and galvanostatic discharge capacity at 1.23 V (830 min, 10 mA cm-2). Moreover, the zinc-air battery based on Pt/C-FeNi-LDH/CA has a small charge-discharge voltage gap (0.65 V) at 10 mA cm-2, after 200 consecutive cycles (66 h), the charge-discharge voltage gap only increased by about 30 mV, indicating good cycling stability.

Orange-peel derived carbon-loaded low content ruthenium nanoparticles as ultra-high performance alkaline water HER electrocatalysts.

Carbon materials have a very wide range of applications in the field of electrocatalysis, both as catalyst bodies and as excellent supports for catalysts. In this work, we obtained a graphitic-like orange-peel derived carbon (OPC) material through pre-carbonization and KOH activation strategies using discarded orange-peel as a raw material. OPC has good graphitization characteristics and a few-layer structure, making it very suitable as a support for nanoparticle catalysts. In order to compare the performance of OPC, we used commercial graphene as the benchmark, made two carbon materials uniformly loaded with ruthenium nanoparticles under the same conditions, and obtained two HER catalysts (Ru/OPC and Ru/rGO). The results indicate that Ru/OPC has excellent HER catalytic performance under alkaline conditions, not only superior to Ru/rGO, but also surpassing commercial Pt/C. In 1 M KOH; the overpotential of Ru/OPC is only 3 mV at -10 mA cm-2, greatly exceeding those of Ru/rGO (100 mV) and Pt/C (31 mV). Under high current density (j), the performance of Ru/OPC is even better; the overpotential is 79 mV and 136 mV at -100 mA cm-2 and -200 mA cm-2, respectively. More importantly, Ru/OPC also has a very high TOF and long-term stability, with a TOF of up to 10.62 H2 s-1 at an overpotential of 100 mV and almost no attenuation after 72 h of operation at -50 mA cm-2. Ru/OPC also exhibits good catalytic performance under acidic conditions, significantly superior to that of Ru/rGO. For Ru/OPC, the overpotential is 86 mV, 167 mV and 214 mV at -10 mA cm-2, -100 mA cm-2 and -200 mA cm-2, respectively. Under the same conditions, the overpotential of Ru/rGO is 143 mV, 253 mV and 306 mV at -10 mA cm-2, -100 mA cm-2 and -200 mA cm-2, respectively.

Ru@N/S/TiO2/rGO: a high performance HER electrocatalyst prepared by dye-sensitization.

Hydrogen production from water-splitting is one of the most promising hydrogen production methods, and the preparation of the hydrogen evolution reaction (HER) catalyst is very important. Although Pt-based materials have the best catalytic activity for HER, their high price and scarcity greatly limit their large-scale industrial application prospects. Herein, a new method to prepare HER catalyst is described, where dyes used in dye-sensitized solar cells (DSSCs) were used as precursors. A high performance HER catalyst (Ru@N/S/TiO2/rGO, Ru nanoparticles (NPs) supported on N/S-doped TiO2/rGO hybrids) was prepared, and the stereoscopic molecular structure of the porphyrin dye, JR1, not only provides a prerequisite for the preparation of the hyperdispersed Ru NPs, but also successfully realizes N/S co-doping. The Ru@N/S/TiO2/rGO shows an excellent catalytic performance for the HER, which is almost the same as that with Pt/C. In 0.5 M H2SO4, the overpotential is 60 mV at 10 mA cm-2, and the Tafel slope is only 51 mV dec-1. In 1 M KOH, the overpotential is only 5 mV at 10 mA cm-2, and the Tafel slope is only 45 mV dec-1, and this performance is much better than most of the HER catalysts that have been reported. When Ru@N/S/TiO2/rGO is utilized as a catalyst in an alkaline water electrolyzer, a bias of only 1.52 V is able to complement overall water-splitting at 10 mA cm-2 (1.78 V, 100 mA cm-2). The molecular structure and coordination metal species of the dyes are easy to adjust, and the the stereoscopic structure is very helpful for inhibiting the aggregation of the metal NPs, and the strong anchoring effect with TiO2 or other carbon materials is also very helpful to achieve heteroatom doping. In addition, the process of dye-sensitization is simple and repeatable, and is a novel and efficient method to prepare the electrocatalyst.

Self-Assembly by Coordination with Organic Antenna Chromophores for Dye-Sensitized Solar Cells.

The development of new sensitizers and new sensitization methods is one of the important means to enhance the conversion efficiency of dye-sensitized solar cells (DSSCs); the ultimate goal is to broaden the spectral response of dyes, reduce electron recombination, and suppress dye aggregation. In this study, we have developed a series of new self-assembled dyes and applied them in DSSCs. We prepared two organic antenna chromophores S1 and S2 and coordinated them with two acceptors A1 and A2 via zinc to construct A-Zn-S series self-assembled dyes. This method is very simple and feasible and can avoid the complex synthesis steps of traditional dyes; the results show that the light-harvesting ability of devices can be improved and charge recombination can be reduced by adjusting the structures of the antenna chromophores and acceptors. The device with A2-Zn-S1 gave a power conversion efficiency of 4.25%, which was higher than those with A1-Zn-S1 (3.88%), A1-Zn-S2 (3.21%), and A2-Zn-S2 (3.52%); the main reason for this is that the different coordination combinations between the antenna chromophore and the acceptor show great differences in Voc and Jsc. The device based on A2-Zn-S1 showed a high Voc of 632 mV and a high Jsc of 9.54 mA cm-2; one reason for this is that S1 has better spectral responsiveness and another reason is that A2 has better steric resistance that effectively reduces charge recombination. Besides, IR spectra indicate that these self-assembled dyes anchored on a TiO2 surface by bicarboxyl anchoring groups are also very beneficial for improving the performance of dyes.

A supramolecular assembly of metal-free organic dye with zinc porphyrin chromophore for dye-sensitized solar cells.

Two porphyrin chromophores, P1 and P2, were prepared and used as antenna units to coordinate with a metal-free organic dye, JH1, containing pyridine groups. This supramolecular self-assembly strategy can not only effectively improve the light-harvesting ability of the devices but also effectively reduces electron recombination by preventing I3- of the electrolyte from penetrating into the TiO2 surface. The DSSC based on JH1 showed a PCE of 2.46%, with a Voc of 615 mV, Jsc of 6.54 mA cm-2, and FF of 61.18%. After supramolecular self-assembly, the Jsc and Voc of the device were greatly improved. Specifically for the device based on JH1 + P2, the PCE reached 4.39%, which is about 78% greater than the PCE of the device based on JH1; this is mainly due to the Jsc increase of 2.85 mA cm-2 and the Voc increase of 93 mV. Compared to co-sensitization, supramolecular self-assembly does not require tedious optimization steps; thus, this may be a promising and convenient way to improve the overall performance of DSSCs.