Search

Some dendritic structures with well-dispersed active sites exposed can often act as electrocatalysts. In this paper, we have developed a kind of composite electrocatalyst Ni:Fe = 7.5:2.5/CF (copper foil) with dendritic FeNi 3 phase prepared by electrodeposition for OER (oxygen evolution reaction). The synthetic material with more crystal surface area and more metal active sites exposed exhibits an excellent electrocatalytic activity. The Ni:Fe = 7.5:2.5/CF electrode sample can drive the OER reaction with the overpotential(ƞ) of 330 mV at 15 mA cm−2 and 490 mV at 50 mA cm−2 respectively. And there is no significant overpotential increase for the Ni:Fe = 7.5:2.5/CF sample at the end of 50000s. The composite synergistic effect between the high active FeNi 3 phase, dendritic morphology and copper foil substrate are the main reason for its excellent electrocatalytic activity. • Electrochemical deposition is one relatively simple synthesis process for electrocatalysts. • The Ni:Fe = 7.5:2.5/CF composite can use the overpotential(ƞ) of 330 mV to drive 15 mA cm−2. • There is no significant overpotential increase for the Ni:Fe = 7.5:2.5/CF at the end of 50000s. • This is mainly attributed to the structure of containing the FeNi 3 dendrite phase. [ABSTRACT FROM AUTHOR]

Transition metal phosphides are emerging as promising electrode materials for energy storage devices because of their higher activity than the oxides counterparts. However, they usually converse to metal hydroxides fast and the P element is depleted during cycles. Here, we report a collaborative optimization strategy by a simple one-step CVD method to address this issue. A synergistic effect between the phosphorization and carbonization significantly enhancing the electrochemical performance of the cobalt oxides is found. The carbonization increases the P content in the sample and the produced carbon layer serving as a protection shell slows the loss of P elements during repeated charging and discharging process. While the phosphorization induces the formation of abundant pores in the carbon layer which is favorable for the electrolyte ions entering into inner active material. Accordingly, the obtained CoO-P/C sample shows high specific capacitance (5 F cm−2 at 10 mA cm−2), excellent rate capability and cyclic stability with 88.6% retention after 5000 cycles at 30 mA cm−2, much better than the samples only treated with P or C modification. In addition, the asymmetric supercapacitor assembled by CoO-P/C and carbon cloth (CC) delivered an energy density of 0.24 mWh cm−2 at a power density of 9.16 mW cm−2, and extraordinary cyclic performance by preserving 181.48% of the initial specific capacitance after 20,000 cycles at 30 mA cm−2. This work provides a simple P/C collaborative optimization strategy to improve the electrochemical performance of metal oxides electrodes. [Display omitted] • P/C collaborative optimization enhances electrochemical performance of CoO. • Carbonization increases P doping content and slows loss of P element during cycles. • Phosphorization induces the formation of pores in the carbon protection shell. • The CoO-P/C electrode presents 5 F cm−2 at 10 mA cm−2. • The assembled device delivers 0.24 mWh cm−2 at 9.16 mW cm−2. [ABSTRACT FROM AUTHOR]

Low electrical conductivity and insufficient active sites of Co-based binary metal oxides or sulfides hamper their practical specific capacitance especially at high current densities. In the current work, we provide a novel synergistic optimization strategy including P doping and constant-current-charge activation (CA) to greatly improve the specific capacitance of sulfur and oxygen-containing Mo-Co binary compounds (Mo-Co-(S,O)) electrode. The synergistic effect of the P doping and activation not only increases the electrical conductivity but also improves the electroactive sites. As a result, the optimized Mo-Co-(S,O)/P-CA electrode shows exceptional specific capacitance (∼9.64 F cm−2/2931 F g−1 at 12.5 mA cm−2), approximately 20 times the pristine Mo-Co-(S,O). Moreover, an asymmetric supercapacitor prepared with Mo-Co-(S,O)/P-CA cathode and conductive carbon cloth achieves a high energy density of 0.61 mWh cm−2 at a power density of 4.25 mW cm−2, and outstanding cyclic performance with 121.6% of capacitance retention after 12,000 cycles. [Display omitted] • Mo-Co-(S,O)/P-CA electrode is used as supercapacitor cathode. • P doping and CA treatment increases the electrical conductivity and improve the electroactive sites of Mo-Co-(S,O). • P doping and CA treatment to greatly improve the specific capacitance of Mo-Co-(S,O). • Mo-Co-(S,O)/P-CA//CC ASC delivers a high energy density and excellent cyclic performance. • A novel and effective approach to boost the specific capacitance of electrode materials. [ABSTRACT FROM AUTHOR]