TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preparation (Claimed): The method of preparing the electrocatalyst involves 1) depositing first metal compound on substrate to form first metal compound-substrate composite by dispersing the substrate into solution containing first metal salt to form dispersion, adding first reagent (preferably hydrogen peroxide) to the dispersion, refluxing dispersion at about 60-100 degrees C for 3-6 hours; 2) depositing active component on first metal compound-substrate composite to form active-first metal compound-substrate composite by dispersing the first metal compound-substrate composite into solvent to form a suspension, adding platinum containing compound to the suspension, refluxing at about 90-140 degrees C for 1.5-4.5 hours; and 3) coating a second metal compound to encase the active-first metal compound-substrate composite to form the electrocatalyst by dispersing active-first metal compound-substrate composite in manganese salt containing solution to form second suspension, adding second reagent (preferably citric acid) into second suspension, and refluxing the second suspension at about 60-100 degrees C for about 2.5-5 hours. Preferred Catalyst: The substrate includes carbon nanotubes and the first metal compound includes a ruthenium containing compound, where the carbon nanotubes and the ruthenium are in a mass ratio of 1:0.02 to 0.15 (preferably 1:0.04 to 0.12). The active component includes platinum, where the ruthenium and platinum are in a mass ratio of 1:0.5 to 2 (preferably 1:1 to 1.5). The second metal compound includes a manganese containing compound, where the ruthenium and the manganese are in a mass ratio of 1:0.5 to 3 (preferably 1:1 to 2.5). Preferred Components: The substrate includes carbon material made of carbon nanotubes. The active component includes noble metal such as platinum, where platinum is in the form of particle. The first metal salt includes ruthenium trichloride or ruthenium oxide. The second metal compound includes manganese dioxide.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - The solvent includes ethylene glycol. EXAMPLE - Carbon nanotubes (CNTs) were dispersed in aqueous ruthenium trichloride solution by sonication, in which the mass ratio of CNTs to ruthenium was 1:0.02 and sonication time was 0.5 hour. Hydrogen peroxide (30 vol.%) was dropwise added with the dropping speed of 9 mL/hour and the ratio of the volume of hydrogen peroxide (30 vol.%) to the ruthenium mass was 1 mL:1 mg. The suspension was refluxed at 60 degrees C. After filtration, washing and drying at 90 degrees C, ruthenium dioxide supported CNTs (RuO2/CNTs composites) were obtained. The resulting RuO2/CNTs were dispersed into ethylene glycol with the addition of chloroplatinic acid, in which the mass ratio of ruthenium to platinum to ethylene glycol was 1:0.5:200. The pH value of the suspension was adjusted to 6.5 and then the suspension was heated to reflux at 90 degrees C for 1.5 hours to obtain platinum nanoparticles supported RuO2/CNTs (Pt/RuO2/CNTs composites). The Pt/RuO2/CNTs was dispersed in deionized water by sonication with addition of potassium permanganate solution. Citric acid solution was dropwise added into the suspension with the mass ratio of ruthenium to manganese to citric acid of 1:0.5:1. The suspension was heated to reflux at 60 degrees C for 2.5 hours. After filtration, washing and drying at 60 degrees C, manganese dioxide covered Pt/RuO2/CNTs (MnO2/Pt/RuO2/CNTs composites) was obtained.