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Hydrogen energy is a promising energy carrier for powering electric vehicles lying in its dense energy and zero pollution. However, the problems of hydrogen production and control have yet to be resolved. Here we present a novel hydrogen production using zinc plate connected to carbon @ nickel electrode in the alkaline solution, where the device works through zinc oxidation at the anode and hydrogen evolution reaction at the cathode. The results demonstrate that the amount of hydrogen production with carbon @ nickel electrode can be improved 5 times higher than that of nickel electrode, and carbon @ nickel electrode can block zinc oxide adsorption upon nickel surface to keep hydrogen production stable. Moreover, hydrogen production is flexibly controlled by means of switching on/off connection between zinc electrode and carbon @ nickel electrode, facilitating to promote hydrogen application. Lastly, the mechanism of hydrogen evolution reaction is analyzed based on electrochemical characterization and density functional theory calculation, displaying that carbon @ nickel electrode can improve electron transfer ability for hydrogen evolution reaction. • Hydrogen production and control is achieved by Zn and C @ Ni contact. • HER rate is enhanced by carbon in coordination with nickel. • The catalytic and mechanistic properties of C @ Ni electrode is analyzed. [ABSTRACT FROM AUTHOR]

Aqueous alkaline Al-air fuel cells receive more attention in the current green energy market. However, interfacial parasitic corrosion of Al anode is a major challenge. For addressing the above problem and improve the energy conversion efficiency of Al anode, we present a dual-protective interface consisting of an inner Zn layer and an outer glutamic acid film. The results show that the 0.35 M glutamic acid can maximize the inhibition of hydrogen evolution corrosion for Al anode by physical adsorption, resulting in reduction of the number and activity of H 2 O molecules on the metal anode surface. Moreover, the groups of –NH 2 and adjacent C O in glutamic acid molecule are regarded as electrophilic attack regions based on density functional theory, while –COOC– in the side chain tends to receive electrons from metal anode. The harmonious interaction between the above groups and the metal surface ensures the stable adsorption of the organic film. Finally, Al-air fuel cell with the dual-protective interface can output the high capacity of 2110.20 mAh g−1 at 20 mA cm−2, achieving anode efficiency of 70.80%. These findings are available for the corrosion inhibition of metal and the preparation of the high-efficiency Al anode. [Display omitted] • A dual-protective interface consisting of inner Zn layer and outer glutamic acid (Glu) film is presented. • Parasitic corrosion of Al anode is inhibited by a dual-protective interface. • Induction mechanism of Glu film on the metal anode is revealed via density functional theory. • Al-air fuel cell achieves a high capacity of 2110.20 mAh g−1 and anode efficiency of 70.80%. [ABSTRACT FROM AUTHOR]

Although Al-air batteries are expected to be the candidates for energy conversion systems in renewable energy market due to the higher energy density, richer reserves, and lighter mass of Al metal, the anode self-discharge is seen as a notorious issue that seriously sacrifices battery durability and stability. Herein, we propose zinc carboxylate inhibition of anode self-discharge for enhancing Al-air battery's lifetime, where the ionized Zn2+ induces a Zn guard on Al surface, and the hydrolysate RCOOH dominates an adsorption layer on the outer surface of Zn, ensuring a double protection for metal anode by means of advanced "one stone two birds" strategy. The results show that the typical zinc carboxylates improve the absolute anticorrosion efficiency of anode greatly, especially the maximum of 92.24% after zinc malate optimization. Furthermore, battery capacity and anode efficiency are as high as 2685.20 mAh g−1 and 90.11% at 20 mA cm−2 respectively. The cyclic discharge lifetime of system (0.12 g fuel) exceeds 19.01 h, which is 1.72 times longer than traditional optimization. Finally, the optimization mechanism is revealed based on Monte Carlo simulation and density functional theory calculation, which the double C O groups in the hydrolysate of zinc malate dominates the harmonious interaction between RCOOH adsorption layer and active metals, exhibiting a high-energy efficiency and long-lifetime Al-air battery power system. [Display omitted] • Advanced optimization strategy is proposed to extend Al-air battery system's lifetime. • Zinc carboxylate enables anode anticorrosion of Al-air battery via a two-step reaction. • Capacity of Al-air battery is as high as 2685.20 mAh g−1 at 20 mA cm−2. • Anode efficiency of Al-air battery achieves 90.11% at 20 mA cm−2. • Cyclic discharge lifetime of Al-air battery is 1.72 times longer than traditional optimization. [ABSTRACT FROM AUTHOR]

[Display omitted] • ZnCl 2 optimization of electrolyte is presented to reduce the anodic self-corrosion. • The optimization mechanism of Lewis acid groups on Al anode surface is revealed. • The anode efficiency of Al-air battery can reach 77.95% at 20 mA/cm2. • The specific capacity of Al-air battery is up to 2322.91 mAh/g at 20 mA/cm2. Al-air batteries are regarded as the potential energy conversion systems due to the ultra-high theoretical specific capacity of 2980 mAh/g and specific energy of 8100 mWh/g for Al anodes. However, the anodic self-corrosion has severely limited the energy efficiency, which induces a great challenge to the commercial penetration of Al-air batteries. Here, we present an alkaline electrolyte optimization with a single inorganic Zn-compound, where a strong Lewis acid ZnCl 2 has the best modification effect for Al-air battery compared with ZnO and ZnCO 3. The results demonstrate that the inhibition efficiency of Al anode is up to 83.03% under the adsorption of strong Lewis acid groups on the Zn protective film. The high specific capacity of 2322.91 mAh/g and specific energy of 2457.02 mWh/g for Al-air battery are obtained at the galvanostatic condition of 20 mA/cm2, and the anode efficiency is enhanced to 77.95% after ZnCl 2 optimization. Moreover, the optimization mechanism is revealed, which provides a technical basis for the application of the enhanced-performance Al-air batteries in the fields of energy conversion and power supply. [ABSTRACT FROM AUTHOR]