A cable-type flexible Zn-air battery with a spiral zinc anode, gel polymer electrolyte (GPE), and air cathode coated on a nonprecious metal catalyst is designed in order to extend its application area toward wearable electronic devices.

Developing low-cost electrocatalysts to replace precious Ir-based materials is key for oxygen evolution reaction (OER). Here, we report atomically dispersed nickel coordinated with nitrogen and sulfur species in porous carbon nanosheets as an electrocatalyst exhibiting excellent activity and durability for OER with a low overpotential of 1.51 V at 10 mA cm −2 and a small Tafel slope of 45 mV dec −1 in alkaline media. Such electrocatalyst represents the best among all reported transition metal- and/or heteroatom-doped carbon electrocatalysts and is even superior to benchmark Ir/C. Theoretical and experimental results demonstrate that the well-dispersed molecular S|NiN x species act as active sites for catalyzing OER. The atomic structure of S|NiN x centers in the carbon matrix is clearly disclosed by aberration-corrected scanning transmission electron microscopy and synchrotron radiation X-ray absorption spectroscopy together with computational simulations. An integrated photoanode of nanocarbon on a Fe 2 O 3 nanosheet array enables highly active solar-driven oxygen production.

The world-wide interest in reducing the dependency on fossil fuels demands the development of energy storage systems with high power density from abundant materials, which would enable wide-spread industrial deployment of grid-scale renewable energy systems, as well as the progressive advancement of high-powered electric vehicles (EVs). Perovskite oxide ceramics attracted significant attention as a strong candidate for bi-functional electrocatalyst for metal-air batteries. There has been consistent investigation on the viability of bi-functional electrocatalysts, because energy storage systems cannot operate rechargeably without the proper bi-functional electrocatalyst. Among various electrocatalysts for both oxygen evolution and reduction, making nanoparticles from these materials for practical applications is a great challenge. The newly introduced pervovskite electrocatalyst of ~50 nm size preferentially reduced oxygen to water (< 5 % peroxide yield), exhibited more than 20 times higher gravimetric activity (A/g) than IrO2 in an OER half-cell test, and surpassed the charge/discharge performance of Pt/C (20 wt%) in a zinc-air full cell test. This study describes substantially the systematic engineering of perovskite ceramics into such a bifunctional nanosized electrocatalyst with high stability and activity, which was also explained in detail from the aspect of defect chemistry. Highly efficient bifunctional oxygen electrocatalysts are indispensable to the development of highly efficient regenerative fuel cells and rechargeable metal-air batteries, which could power future electric vehicles. Although perovskite oxides are known to have high intrinsic activity, large particle sizes rendered from traditional synthesis routes limit their practical use due to low mass activity. We report the synthesis of nano-sized perovskite particles with a nominal composition of L ax(Ba0.5Sr0.5)1-xCo0.8Fe0.2O3-d (BSCF), where lanthanum concentration and calcination temperature were controlled to influence oxide defect chemistry and particle growth. This approach produced a bifunctional perovskite electrocatalyst of ~50 nm size with supreme activity and stability for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The electrocatalyst preferentially reduced oxygen to water (<5 % peroxide yield), exhibited more than 20 times higher gravimetric activity (A/g) than IrO2 in an OER half-cell test (0.1 M KOH), and surpassed the charge/discharge performance of Pt/C (20 wt%) in a zinc-air full cell test (6 M KOH).Our work provides a general strategy for designing perovskite oxides as inexpensive, stable and highly active bifunctional electrocatalysts for future electrochemical energy storage and conversion devices.The world-wide interest in reducing the dependency on fossil fuels demands the development of energy storage systems with high power density from abundant materials, which would enable widespread industrial deployment of grid-scale renewable energy systems, as well as the progressive advancement of...

A facile H O oxidation treatment to tune the properties of metal disulfides for oxygen evolution reaction (OER) activity enhancement is introduced. With this method, the degree of oxidation can be readily controlled and the effect of surface S residues in the resulted metal (oxy)hydroxides for the OER is revealed for the first time. The developed NiFe (oxy)hydroxide catalyst with residual S demonstrates an extraordinarily low OER overpotential of 190 mV at the current density of 10 mA cm after coupling with carbon nanotubes, and outstanding performance in Zn-air battery tests. Theoretical calculation suggests that the surface S residues can significantly reduce the adsorption free energy difference between O* and OH* intermediates on the Fe sites, which should account for the high OER activity of NiFe (oxy)hydroxide catalysts. This work provides significant insight regarding the effect of surface heteroatom residues in OER electrocatalysis and offers a new strategy to design high-performance and cost-efficient OER catalysts.

One of the key challenges that hinders broad commercialization of proton exchange membrane fuel cells is the high cost and inadequate performance of the catalysts for oxygen reduction reaction (ORR)....