Metal-organic interface engineering for boosting the electroactivity of Pt nanodendrites for hydrogen production

Recently, the surface chemical functionalization and morphology control of precious metal nanostructures have been recognized as two efficient strategies for improving their electroactivity and/or selectivity. In this work, 1, 10-phenanthroline monohydrate(PM) functionalized Pt nanodendrites(Pt-NDs) on carbon cloth(CC)(denoted as PM@Pt-NDs/CC) and polyethylenimine(PEI) functionalized Pt-NDs on CC(denoted as PEI@Pt-NDs/CC) are successfully achieved by immersing Pt-NDs/CC into PM and PEI aqueous solutions, respectively. PEI functionalization of Pt-NDs/CC improves its electroactivity for hydrogen evolution reaction(HER) due to local proton enrichment whereas PM functionalization of Pt-NDs/CC improves its electroactivity for formic acid oxidation reaction(FAOR) by facilitating dehydrogenation pathway. With such high activity, a two-electrode electrolyzer is assembled using PM@Pt-NDs/CC as the anodic electrocatalyst and PEI@Pt-NDs/CC as the cathodic electrocatalyst for electrochemical reforming of formic acid, which only requires 0.45 V voltage to achieve the current density of 10 mA cm^(-1) for highpurity hydrogen production, much lower than conventional water electrolysis(1.59 V). The work presents an example of interfacial engineering enhancing electrocatalytic activity and indicates that electrochemical reforming of formic acid is an energy-saving electrochemical method for high-purity hydrogen production.

Organic ammonium halides enhance the performance of Pb-Sn perovskite solar cells

With the efforts of scientists around the world,the power conversion efficiency(PCE)of perovskite solar cells(PSCs)has reached 25.7%.To further improve the efficiency and break through the Shockley-Queisser(S-Q)limit,it is promising to construct all-perovskite tandem solar cells via combining wide-bandgap and narrow-bandgap perovskites[1−5].As the key light-harvesting material for the bottom cell in all-per-ovskite tandem devices,the narrow-bandgap Pb-Sn mixed per-ovskites have attracted increasing interest in recent years[6−8].However,the Pb-Sn mixed perovskites suffer from uncontrol-lable crystallization,easy oxidation of Sn2+and high defect density,which significantly limit PCE improvement[9,10].Organ-ic ammonium halides can improve the efficiency and stabil-ity of Pb-Sn mixed PSCs.

Au core-PtAu alloy shell nanowires for formic acid electrolysis

Inefficient electrocatalysts and high-power consumption are two thorny problems for electrochemical hydrogen(H2)production from acidic water electrolysis.Herein we report the one-pot precise synthesis of ultrafine Au core-Pt Au alloy shell nanowires(Au@PtxAu UFNWs).Among them,Au@Pt_(0.077) Au UFNWs exhibit the best performance for formic acid oxidation reaction(FAOR)and hydrogen evolution reaction(HER),which only require applied potentials of 0.29 V and-22.6 m V to achieve a current density of 10 m A cm^(-2),respectively.The corresponding formic acid electrolyzer realizes the electrochemical H2 production at a voltage of only 0.51 V with 10 m A cm^(-2) current density.Density functional theory(DFT)calculations reveal that the Au-riched Pt Au alloy structure can facilitates the direct oxidation pathway of FAOR and consequently elevates the FAOR activity of Au@Pt_(0.077) Au UFNWs.This work provides meaningful insights into the electrochemical H_(2) production from both the construction of advanced bifunctional electrocatalysts and the replacement of OER.

Highly Efficient Dye-sensitized Solar Cells by Co-sensitization of Organic Dyes and Co-adsorbent Chenodeoxycholic Acid

Approach to highly efficient dye-sensitized solar cells(DSSCs)by co-sensitization of organic dyes,AZ6+AZ5 with co-adsorbent chenodeoxycholic acid(CDCA)is presented.The power conversion efficiencies(PCEs)of 8.55%and 8.31%are obtained from DSSCs co-sensitized by AZ6(0.3 mmol/L)+AZ5(0.1 mmol/L)with CDCA concentration of 5 and 20 mmol/L in one step cocktail,respectively.The latter shows high stability in a period of 653 h under ambient conditions.

Defects in perovskite crystals

Perovskite solar cell(PSC) is now a shining star in photovoltaics field[1].Benefiting from excellent optoelectronic properties of perovskite materials,the certified power conversion efficiency(PCE)of PSCs has reached 26.0%[2],showing great potential for commercialization.In essence,the efficiency of solar cells is determined by the radiative and nonradiative recombination of photogenerated charge carriers.The unfavorable nonradiative recombination mainly assisted by the trap states leads to severe charge carrier loss and thus unsatisfactory efficiency.

N-doped carbon nanocages： Bifunctional electrocatalysts for the oxygen reduction and evolution reactions

Highly effident metal-free, carbon-based, bi-functional electrocatalysts for the oxygen evolution reaction （OER） and oxygen reduction reaction （ORR） have attracted increased attention for use in electrochemical energy conversion systems, owing to their low cost and high activity. In this work, N-doped carbon nanocages （N-CCs） with a porous self-supported architecture and high specific surface area are synthesized by a facile interfacial assembly synthetic route. The materials are comprehensively characterized by scanning electron microscop36 transmission electron microscopy, nitrogen adsorption-desorption experiments, X-ray diffraction, and X-ray photoelectron spectroscopy. Cyclic voltammetry , chronoamperometry, and linear sweep voltammetry demonstrate that the as-prepared N-CC could serve as an effective metal-free electrocatalyst with excellent catalytic activity, long-term operation durability, and excellent methanol tolerance for the ORR in alkaline media. In the presence of 3 mM methanol, the half wave potential of the N-CCs for the ORR is 190 mV; this is more positive than that of the commercial Pt/C electrocatalyst. Meanwhile, the N-CCs also show an OER activity comparable to that of the commercial Ru/C electrocatalyst, revealing their bifunctional property.

Spinel MnCo2O4 nanoparticles cross-linked with two-dimensional porous carbon nanosheets as a high-efficiency oxygen reduction electrocatalyst

Catalysts for the oxygen reduction reaction （ORR） play an important role in fuel cells. Alternative non-precious metal catalysts with comparable ORR activity to Pt-based catalysts are highly desirable for the development of fuel cells. In this work, we report for the first time a spinel MnC0204/C ORR catalyst consisting of uniform MnC0204 nanoparticles cross-linked with two-dimensional （2D） porous carbon nanosheets （abbreviated as porous MnC0204/C nanosheets）, in which glucose is used as the carbon source and NaC1 as the template. The obtained porous MnCo204/C nanosheets present the combined properties of an interconnected porous architecture and a large surface area （175.3 m2-g-1）, as well as good electrical conductivity （1.15 x 102 S.cm-1）. Thus, the as-prepared MnC0204/C nanosheets efficiently facilitate electrolyte diffusion and offer an expedite transport path for reactants and electrons during the ORR. As a result, the as-prepared porous MnC0204/C nanosheet catalyst exhibits enhanced ORR activity with a higher onset potential and current density than those of its counterparts, including pure MnC0204, carbon nanosheets, and Vulcan XC-72R carbon. More importantly, the porous MnC0204/C nanosheets exhibit a com- parable electrocatalytic activity but superior stability and tolerance toward methanol crossover effects than a high-performance Pt/C catalyst in alkaline medium. The synthetic strategy outlined here can be extended to other non- precious metal catalysts for application in electrochemical energy conversion.