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Alcohol electrooxidation reaction (AOR) is of sluggish kinetics, which as the anodic reaction of direct alcohol fuel cells determines largely the discharging performance of the device. Solar energy as an endless energy source is introduced to promote the AOR kinetics. Herein, the recent progress on photo‐promoted AOR and the application in fuel cells is reviewed, including 1) design of the AOR photoelectrocatalysts, 2) photoelectrocatalysis mechanism, and 3) fabrication of photo‐promoted direct alcohol fuel cells (PDAFCs). Finally, a perspective on the challenges of PDAFCs and new directions in this exciting and still emerging research area are given. [ABSTRACT FROM AUTHOR]

Zinc-oxygen batteries are promising candidates for electrical vehicles and electric grid energy storage due to their low cost, high safety levels, and low environmental impact. The oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) represent the most significant processes in zinc-oxygen batteries. The development of nonprecious metal catalysts for OER with satisfactory performances and low cost (especially prepared by a straightforward synthesis route), still poses a significant challenge. Herein, we report an exceptionally facile and easily scalable method to produce NiFe layered double hydroxide (LDH) coated nickel foam by immersing nickel foams into aqueous solutions containing NiCl2 and FeCl2 and keeping them standing for a certain period of time. Without any other complicated technique or organic reagent, microflower-shaped NiFe LDHs can be obtained. The resulting electrode shows excellent OER performance with a low overpotential of 210 mV at a 10 mA cm−2 constant current polarization and stable operation for more than 100 charge-discharge cycles in zinc-oxygen batteries. [ABSTRACT FROM AUTHOR]

Abstract: A series of Ni modified MnO x /C composites were synthesized by introducing NaBH4 to MnO2/C aqueous suspension containing Ni(NO3)2. The physical properties and the activity of the composites toward the oxygen reduction reaction (ORR) were investigated via transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and the electrochemical techniques. The results show that the higher activity of the composites toward the ORR is correlated with the higher content of MnOOH species transformed from Mn(II) on the surface of the composite. The main nickel species in the composites is Ni(OH)2, while Ni(OH)2 shows little activity toward the ORR. However, introducing Ni(OH)2 with proper amount into the MnO x /C improves the distribution of the active material MnO x , which contributes to a surface with more MnOOH. The optimal composite is of the Ni/Mn atomic ratio of 1:2 and the MnO x loading of 28 wt.%. The maximum power density of the zinc–air battery with the optimized Ni modified MnO x /C as the cathode catalyst reaches up to 122 mW cm−2, much higher than the one with the MnO x /C as the air cathode catalyst (89 mW cm−2), and slightly higher than those with the Pd/C and Pt/C as the cathode catalysts. [Copyright &y& Elsevier]

Abstract: Carbon-supported bimetallic PdAg catalysts with Pd/Ag atomic ratios varying from 4/1 to 1/2 were prepared by an impregnation–reduction method. The impregnated black mixture was treated in H2/N2 atmosphere at a temperature varying from 180 to 500°C. The obtained Pd x Ag y /C catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), cyclic voltammetry (CV) and chronoamperometry (CA). XRD results show that the lattice constant of Pd is dilated, suggesting the formation of PdAg alloy. The lattice constant of Pd for the Pd x Ag y /C-500 (reduced at 500°C by H2) increases linearly and the average metal particle size decreases slightly from 6.8 to 5.1nm with increasing Ag fractions from 20% to 67% in the PdAg composition. For Pd x Ag y /C catalysts with a certain specific Pd/Ag atomic ratio, e.g., Pd2Ag1/C, the dilated lattice constant of Pd is independent of the reducing temperature, indicating the alloy degree for the Pd2Ag1/C-t catalysts is comparable. The average metal particle size for the Pd2Ag1/C-t catalysts increases from 3.4 to 5.2nm with H2 reduction temperature increasing from 180 to 500°C. The potentiodynamic measurements on ethanol electrooxidation reaction (EOR) show that the catalytic activities for the Pd x Ag y /C-t catalysts toward the EOR are improved by alloying Pd with Ag. At typical potential of a working fuel cell, e.g., −0.4V vs. Hg/HgO, the EOR current density presents a volcano shape as a function of the Ag fractions in PdAg with the maximum occurs at the Pd/Ag atomic ratios between 2/1 and 3/1. The CA tests show that the Pd x Ag y /C-500 catalysts perform high stability than that of Pd/C-500. The improved EOR activity for the Pd x Ag y /C-t catalysts, compared with whether Pd/C or Ag/C catalyst, may possibly be attributed to the formation of PdAg alloy and the fitted particle size. [Copyright &y& Elsevier]

Abstract: A graphitic mesoporous carbon (denoted as GMC) was synthesized using resorcinol and formaldehyde as carbon precursors and iron nitrate as a graphitization catalyst. The GMC was characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy (TEM), and nitrogen adsorption. The results show that the GMC has a mesoporous structure and a high surface area of 403 m2 g−1, and particularly, a well-defined graphitic framework. Using the GMC as the support, a PtRu/GMC was synthesized to act as an electrocatalyst for the methanol oxidation reaction (MOR). A counterpart with Vulcan® XC-72 (denoted as XC) as the support was prepared for comparison. TEM images show that PtRu nanoparticles are distributed uniformly on the carbon supports for both electrocatalysts. The electrochemical activity of the PtRu/GMC toward the MOR is slightly higher than that of the PtRu/XC in both half cell and single cell measurements. The 1500h stability test of a single cell suggests that the PtRu/GMC is excellent stable. [Copyright &y& Elsevier]

Abstract: To investigate the effect of carbon support adding sequence on Pt particle sizes and Pt utilizations during the polyol process of the electrocatalyst preparation, a series of Pt/C electrocatalysts (different Pt loadings, two kinds of carbon supports−Vulcan XC and Black Pearls 2000) were prepared, namely, Pt/C-a (first reduced Pt ions to form Pt nanoparticles, which subsequently deposited on carbon supports) and Pt/C-b (Pt precursors were first impregnated with carbon supports, then reduced to Pt nanoparticles). The physical properties of the electrocatalysts were characterized by X-ray diffraction, transmission electron microscopy and nitrogen adsorption. The catalytic activities of the electrocatalysts toward the oxygen reduction reaction and the methanol oxidation reaction were characterized by potentiodynamic measurements. The results show that the carbon support adding sequence has significant effects on the Pt particle sizes, especially for the carbon supports with large amount of micropores, as a result, leading to different catalytic activities. [Copyright &y& Elsevier]

Abstract: Carbon-supported bimetallic Pt m Pb1 (m =1, 2, 3) electrocatalysts with different Pt/Pb atomic ratios were synthesized by a polyol method. The X-ray diffraction results reveal that a PtPb alloy formed in the Pt m Pb1/C electrocatalysts. TEM images show that the PtPb nanoparticles distribute uniformly on the carbon support, and are about 4–5nm in size. The Pt m Pb1/C bimetallic catalysts show superior activities toward methanol electrooxidation reaction (MOR) than the Pt/C in alkaline media. Both CO stripping measurements and density functional theory studies reveal that CO adsorption decreased significantly on the Pt m Pb1/C bimetallic catalysts compared with on pure Pt, which may offer an explanation for the enhanced MOR activity of the Pt m Pb1/C bimetallic catalysts. [Copyright &y& Elsevier]

Abstract: A carbon supported PtNi/C electrocatalyst synthesized via a polyol process was characterized by XRD, TEM and voltammetry techniques. The XRD analysis showed a decreased lattice constant of Pt for the PtNi/C catalyst compared with the Pt/C, indicating partial PtNi alloy formed. The PtNi/C exhibited enhanced mass activity towards methanol oxidation reaction as well as decreased CO stripping currents in alkaline media compared with the Pt/C. Density functional theory studies revealed the electronic structure modification of Pt by Ni atoms and weakened CO adsorption energy on the Pt3Ni than on the Pt4 clusters, which may account for the increased MOR activity. [ABSTRACT FROM AUTHOR]

Abstract: We synthesized and characterized a highly active electrocatalyst for oxygen reduction reactions (ORRs) in alkaline media by coating carbon-supported silver nanoparticles with Pd (Pd@Ag/C) via a galvanic displacement method. The electrochemical measurements were carried out using an ultrathin film rotating disk electrode. Compared to the Pt/C electrocatalyst, the specific and mass activities of the Pd@Ag/C were enhanced by a factor of 3 and 2.5, respectively. The potentiostatic measurements showed that the Pd@Ag/C is less stable than the Pt/C at the potential of −0.1V vs. Hg/HgO/OH− in alkaline media. The Pd@Ag/C is insensitive to alcohol, and, as a cathode electrocatalyst of a direct alcohol fuel cell, can resist poisoning by the possible alcohol crossover from the anode. [Copyright &y& Elsevier]

Abstract At present, it is difficult for electrocatalytic electrode materials with high-Performance to be prepared at low cost and large area under mild conditions. Therefore, we adopt a facile electroless plating method to deposit the Fe Co P alloys on the nickel foam (NF) with different areas of 1 cm2, 4 cm2, 8 cm2 and 16 cm2. The Fe Co P/NF catalysts exhibit extraordinary catalytic activity for the oxygen evolution reaction (OER) in alkaline media and are comparable to the state-of-the-art IrO 2 in 1.0 M KOH, capable of yielding a current density of 10 mA cm−2 at an overpotential of only 250 mV. Furthermore, the Fe Co P/NF catalysts show efficient activity towards the hydrogen evolution reaction (HER) with an overpotential of 163 mV at j = 10 mA cm−2 as well. Remarkably, when used as both the anode and cathode, a low potential of 1.68 V (vs. RHE) is required to reach the current density of j = 10 mA cm−2, making the Fe Co P/NF alloys as an active bifunctional electrocatalyst for overall water splitting. The Fe Co P/NF alloy catalysts with high catalytic activity, facile preparation and low cost would provide a new pathway for the design and large-scale application of high-performance bifunctional catalysts for electrochemical water splitting. Highlights • The Fe Co P/NF electrocatalysts were prepared by electroless deposition technology. • This alloy is an bifunctional electrocatalyst for overall water splitting. • Preparation without restriction of matrices can extend to large areas. • The catalytic mechanism of overall water splitting is carefully studied. [ABSTRACT FROM AUTHOR]

[Display omitted] • A unique Ni/Ru hetero-nano-twin catalyst with rich interfaces. • Electron re-distribution at interfaces of Ni/Ru twins balances H ad /OH ad adsorption. • Ni 1 Ru 1 twin shows superior activity for alkaline HOR/HER as compared to Pt/C. • Ni 1 Ru 1 twin is remarkably stable with a break-down potential up to 0.25 V RHE. • The crucial role of the intimate Ni/Ru nano-twin is demonstrated and discussed. Herein, unique Ni-Ru nano-twins (Ni 1 Ru 1 /C) are reported for the first time as a superior bifunctional catalyst for hydrogen oxidation/hydrogen evolution reaction (HOR/HER). Compared to Pt/C, the Ni 1 Ru 1 /C nano-twins display a remarkable HOR activity with a comparable mass activity of 0.12Amg−1 metal and superior HER activity, with an overpotential (դ) of only 16 mV for achieving a cathodic HER current of 10mAcm−2, together with a high turnover-frequency of 1.88 s−1 (@դ=30 mV). Additionally, the HOR limiting current of the Ni 1 Ru 1 /C nano-twins can be maintained up to a break-down potential of 0.25V RHE , demonstrating excellent electrochemical stability. Experimental and theoretical studies reveal that the electron re-distribution at the Ni/Ru interface of Ni-Ru nano-twins optimizes the binding energy of the adsorbed hydrogen (H ad) and the adsorbed hydroxyl (OH ad) intermediates, allowing the HOR/HER to proceed via a low energy barrier. This work provides a strategy to synthesize hetero-metal nano-twins as promising multi-functional catalysts and highlights the critical role of interfaces for heterostructured electrocatalysts. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the reversible and the irreversible loss in performance of direct methanol fuel cell (DMFC) single cells induced by freeze/thaw cycling are determined and discussed. The reversible loss in performance is attributed to the decreased activity of electrocatalysts due to the strong adsorption of the intermediates from methanol electro-oxidation at subzero temperatures, while the irreversible loss in performance is due to the damage of membrane electrode assembly (MEA) structure. It is found that the reversible degradation of performance is dominant when the cell operated at low current densities with O2; the irreversible degradation is more obvious when the cell discharged at high current densities or operated with air. A method, applying a reverse current on the single cell, is put forward to recover the reversible loss in performance. By this method, the voltage of the single cell operated with O2 at 100 mA cm−2 drops only about 16 mV after experiencing 100 freeze/thaw cycles between−10 and 60 °C. [Copyright &y& Elsevier]

Abstract: Well dispersed PtSn/C, PtRu/C and Pt/C electrocatalysts were synthesized by a modified polyol process and characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and inductively coupled plasma-atomic emission spectrometry techniques. XRD patterns show that Ru induces the contraction of Pt lattice parameter while Sn makes the Pt crystal lattice extended. Ethanol oxidation activities on the catalysts were studied via cyclic voltammetry (CV) and chronoamperometry (CA) methods at room temperature. It is found that the electrode potential plays an important role in the electrochemical behavior of ethanol oxidation on PtRu/C and PtSn/C catalysts. In the lower potential region, PtSn/C possesses higher performance for ethanol oxidation, while in the higher potential region PtRu/C is more active. The different promotion effects of PtSn/C and PtRu/C to ethanol oxidation can be explained by the structural effect and modified bi-functional mechanism in different potential region. Single cell test of a direct ethanol fuel cell (DEFC) was also carried out to elucidate the promotion effect of PtRu/C and PtSn/C catalysts on the ethanol oxidation at 90°C. [Copyright &y& Elsevier]

One of the main challenges for electrochemical water splitting is to develop low-cost and efficient oxygen evolution anode materials. In this work, the Co–P alloys as efficient electrocatalysts for oxygen evolution reaction in alkaline media have been successfully synthesized by using electroless plating under mild conditions. SEM, TEM and XRD characterization show that the amorphous Co–P/NF electrocatalysts have rough surface structures, exposing more active sites for oxygen evolution reaction. The electrochemical measurements confirm that Co–P alloys have excellent activity for oxygen evolution reaction, with an overpotential of 306 mV (at j = 10 mA cm−2), a lower Tafel slope of 51.1 mV dec−1 and long-term stability (>25 h) under alkaline conditions (1.0 M KOH). Image 101 • The Co–P/NF electrocatalysts are prepared by electroless deposition technology only need 10 min under mild conditions. • The change of Co–P/NF electrocatalysts after the stability test is carefully studied. • The OER activity can be maximumly promoted and maintained for Co–P/NF catalyst. • This work provides an important platform for further industrial production. [ABSTRACT FROM AUTHOR]