In this paper, Ag-Functionalized graphene electrocatalyst was prepared by simultaneous reduction of Ag[(NH3)2]+ and graphene oxide (GO) under the protection of Poly Diallyldimethylammonium Chloride. The as-prepared catalyst was utilized to enhance the catalytic activity toward oxygen reduction reaction (ORR) in energy-saving electrolysis of Na2CO3. The morphology characterization indicates that Ag nanoparticles uniformly disperse on the surface of reduced graphene oxide (RGO), and their average size is only about 5.7 nm. The electrochemical tests show that the as-prepared catalyst exhibits high electrocatlytic activity for ORR in alkaline media. Furthermore, when the catalyst is used for the oxygen reduction cathode (ORC) in the galvanostatic electrolysis of Na2CO3, the cell voltage can be reduced by 1.05 V, as compared with the conventional hydrogen evolution cathode (HEC) electrolysis. Correspondingly, up to 41.5% electrical energy consumption is saved at the same current density of 100 mA cm–2.

•NiFe-LDHs nanosheets are prepared by a new facile and scalable preparation method.•The sample exhibits excellent catalytic activity and stability toward oxygen evolution reaction.•The sample containing 15% Fe exhibits a superior OER performance to 20% Ir/C.Recently, numerous researches have been conducted to develop non-precious metal catalysts for oxygen evolution reaction (OER), among which NiFe oxyhydroxides as the efficient catalysts have been intensively investigated. Herein, we demonstrate NiFe layered double hydroxides (NiFe-LDHs) nanosheets as highly active OER catalysts, which are synthesized by a facile, scalable and template free method. The ordered nanosheets structure of NiFe-LDHs with Fe contents from 0 to 25% was obtained at low temperature with precisely controlled the pH value by complexation-precipitation process. Compared with 20% commercial Ir/C, the obtained sample with 15% Fe exhibits superior catalytic performance in 1 mol L−1 KOH solution. Its overpotential and Tafel slope are, 216 mV and 37 mV dec−1, lower than that of 20% Ir/C (330 mV and 130 mV dec−1) respectively at a current density of 10 mA cm−2. Furthermore, it also exhibits superior stability and durability to 20% Ir/C in 15 h galvanostatic polarization experiments.

•The Ni(OH)2/C composite electrode provides ultrahigh charge-discharge speed of 50C.•The Ni(OH)2/C composite offers a larger discharge specific capacity of 345.2 mAh g−1.•The materials exhibits excellent cycle life during the 20000 cycles.Nickel hydroxide is widely used as cathode materials in metal hydride–Ni (MHNi) and Cd–Ni rechargeable batteries and the asymmetric supercapacitors due to its good electrochemical properties and affordable prices. The specific capacity and cycle life of Ni(OH)2 are greatly declined at high current density due to its P-type semiconductor structure and the mechanism of solid-phase proton diffusion. The paper thus proposes a new controllable complexing–precipitation method to prepare nano-Ni(OH)2 sheets on mesoporous carbon particles, denoted as nano-Ni(OH)2/C composite. Because of the “fusion effect” of the Ni(OH)2 and mesoporous carbon, a sample with 20% carbon can offer 345.2 mAh g−1 at ultrahigh current density of 30 A g−1 which are higher than that of its theoretical one-electron capacity (291 mAh g−1) of Ni(OH)2 during the first 20,000 cycles. Furthermore, the capacity still keeps up to 97% of the initial capacity, which exhibits a superior electrochemical property than the existing Ni(OH)2. The nano-Ni(OH)2/C composite (20% carbon) exhibits a superior electrochemical property than the reported existing Ni(OH)2 and Ni(OH)2/carbon composites in the literature.

Although N-doped graphene-based electrocatalysts have shown good performance for oxygen reduction reaction (ORR), they still suffer from the single-type active site in the as-prepared catalyst, limited accessible active surface area because of easy aggregation of graphene, and harsh condition for preparation process of graphene. Therefore, further developing a novel type of graphene-based electrocatalyst by a facile and environmentally benign method is highly anticipated. Herein, we first fabricate a sandwich-like graphene/carbon hybrid using graphene oxide (GO) and nontoxic starch. Then the graphene/carbon hybrid undergoes postprocessing with iron(III) chloride (FeCl3) and potassium sulfocyanide (KSCN) to acquire N-doped graphene/carbon nanosheets decorated by Fe and S. The resultant displays the features of interpenetrated three-dimensional hierarchical architecture composed of abundant sandwich-like graphene/carbon nanosheets and low graphene content in as-prepared sample. Remarkably, the obtained catalyst possesses favorable kinetic activity due to the unique structure and synergistic effect of N, S, and Fe on ORR, showing high onset potential, low Tafel slope, and nearly four-electron pathway. Meanwhile, the catalyst exhibits strong methanol tolerance and excellent long-term durability. In view of the multiple active sites, unique hierarchical structure, low graphene content, and outstanding electrochemical activity of the as-prepared sample, this work could broaden the thinking to develop more highly efficient graphene/carbon electrocatalysts for ORR in fuel cells.

Hierarchical nitrogen-doped porous graphene/carbon (NPGC) composites were fabricated by a simple and nontemplate method. The morphology characterizations demonstrate that reduced graphene oxide was successfully coated by the carbon derived from glucose, and a well-organized and interpenetrated hierarchical porous structure of NPGC was formed after pyrolysis at 950 °C. Notably, the prepared material, denoted as NPGC-950, has superlarge specific surface area (1510.83 m2 g–1) and relatively high content percentage of pyridinic and graphitic nitrogen. As an efficient metal-free electrocatalyst, NPGC-950 exhibits a high onset potential (0.91 V vs RHE) and a nearly four-electron pathway for oxygen reduction reaction in alkaline solution as well as stronger methanol tolerance and better long-term durability than commercial Pt/C. In view of these excellent features, the obtained hierarchical N-doped metal-free porous carbon material is a promising catalyst for oxygen reduction reaction and could be widely applied in industry.Keywords: graphene/carbon composites; hierarchical porous structure; metal-free; nitrogen doped; oxygen reduction reaction

This paper reports a new method of direct recovery of highly pure lead oxide (PbO) from waste lead pastes and lead grids of spent lead–acid batteries via catalytic conversion, desulfurization, and recrystallization processes in sequence. On the basis of the analytical results of lead (Pb) and lead dioxide (PbO2) contents in the scrap lead paste, a certain amount of waste lead grid was used as a reductant to transform the excess PbO2 into lead sulfate (PbSO4). This paper systematically studies the influence of the concentration of sulfuric acid (H2SO4) and catalyst and the reaction temperature on the catalytic process. The desulfurization of the obtained PbSO4 and the recrystallization of PbO in sodium hydroxide (NaOH) solutions of different concentrations are also investigated. Furthermore, electrochemical experimental results show that the prepared α-PbO with high purity provides slightly superior electrochemical performance to the existing lead oxide obtained by the Shimadzu ball-milling method during the first 350 charge–discharge cycles in the cycling test.

This paper reports an energy-saving electrolysis of Na2CO3 to generate NaHCO3 and NaOH for efficient production of alumina. Silver nanoparticles catalyzed oxygen reduction cathode (Ag NPs ORC) is employed to substitute conventional cathode (hydrogen evolution cathode: HEC). Scanning electron microscopy (SEM) image shows that silver nanoparticles ranging from 15 to 50 nm are evenly distributed on the surface of the carbon support. The constant current electrolysis indicates that the cell voltage of Ag NPs ORC electrolysis of Na2CO3 is as low as 1.52 V and correspondingly the electrical energy consumption is saved up to 39.8% as compared to HEC electrolysis at the same current density of 100 mA cm− 2.It reports an energy-saving electrolysis of Na2CO3 by using sliver nanoparticles catalyzed oxygen reduction cathode (ORC) to substitute hydrogen evolution cathode (HEC). The electrical energy consumption of ORC electrolysis is saved up to 39.8% as compared to that of conventional HEC electrolysis.Highlights► This paper reports an energy-saving electrolysis of Na2CO3 by using Ag NPs ORC. ► Silver nanoparticles ranging from 15 to 50 nm are evenly distributed on ORC. ► The cell voltage of ORC-electrolysis is as low as 1.52 V at 100 mA cm− 2. ► The electrical energy consumption is saved up to 39.8% as compared to that of HEC electrolysis.

This paper reports a new lead recovery method, in which high purity metallic Pb is directly produced by electrolyzing PbO obtained from waste lead acid batteries in alkaline solution. The sodium ionic exchange membrane is used to avoid HPbO2− being oxidized to PbO2 on the anode. The new system is not only low energy consuming, but also beneficial to improving the lead recovery efficiency. Furthermore, the new recovery process realizes the circulation of the waste electrolyte, avoiding emission of lead effluent. The effect of concentration of NaOH solution on the cell voltage of the electrolytic bath was studied. Experimental results indicate that the cell voltage of electrolytic bath is 1.23 V, the current efficiency is 99.9%, the lead recovery efficiency is 99.8% and the energy consumption reaches 317 kWh ton Pb− 1 at a current density of 20 mA cm− 2.Highlights► This paper reports a new lead recovery technology by eletrolyzing alkaline PbO solution. ► The appropriate concentration of NaOH in catholyte should be controlled at 15–20%, and that in anolyte at 30%. ► The energy consumption per ton lead is as low as 317 kWh at 20 mA cm− 2. ► The recovery rate of Pb can reach up to 99.8% in the electrolytic process.