Hydrogen peroxide (H 2 O 2), first synthesized in 1818 through the acidification of barium peroxide (BaO 2) with nitric acid, is a clear and colorless liquid which is entirely miscible with water and variety of organic solvents such as carboxylic acid and esters. Anthraquinone process (an old production process of H 2 O 2), a batch process carried out in large facilities is an energy demanding process that requires large facilities, and involves oxidation of anthraquinone molecules and sequential hydrogenation. Moreover, the direct synthesis method enables production in a continuous mode as well as it permits small scale, decentralized production. Many drawbacks associated with these processes such as, energetic inefficiency and inherent disadvantages have motivated researchers, industry and academia to find out alternative for synthesis of H 2 O 2. Electrochemical route based on catalyst selectively reduce oxygen to hydrogen peroxide. O 2 is cathodically reduced to produce H 2 O 2 via 2-electron pathway or 4-electron pathway to get H 2 O. Electrolysis of water has an important place in storage and electrochemical energy conversion process where problem is to choose a sufficiently stable and active electrode for anodic oxygen evolution reaction. Most commonly used catalysts on the cathode are carbon based materials such as carbon black, carbon nanotubes, graphite, carbon sponge, and carbon fiber. In perspective of expanding demand of production and usage of hydrogen peroxide we review the past literature to summarize different production processes of H 2 O 2. In this review, we mainly focus on electrochemical production of hydrogen peroxide along with other alternatives, such as anthraquinone method for industrial H 2 O 2 production and direct synthesis process. We also review the catalytic activity, selectivity and stability for enhanced yield of H 2 O 2. From revision of last two decade's literature including experimental and theoretical data; we argue that successful implementation of electrochemical H 2 O 2 production can be realized on the basis of stable, active and selective catalyst.
With the development of industrialization and urbanization, metal and metalloid pollution is one of the most serious environmental problems in China. Current contamination status of metals and metalloid and their potential ecological risks along China's coasts were reviewed in the present paper by a comprehensive study on metal contents in marine waters and sediments in the past few decades. The priority metals/metalloid cadmium (Cd), mercury (Hg), chromium (Cr), lead (Pb), and arsenic (As), which were the target elements of the designated project "Comprehensive Prevention and Control of Heavy Metal Pollution" issued by the Chinese government in 2011, were selected considering their high toxicity, persistence, and prevalent existence in coastal environment. Commonly used environmental quality evaluation methods for single and combined metals were compared, and we accordingly suggest the comprehensive approach of joint utilization of the Enrichment Factor and Effect Range Median combined with Pollution Load Index and Mean Effect Range Median Quotient (EEPME); this battery of guidelines may provide consistent, internationally comparable, and accurate understanding of the environment pollution status of combined metals/metalloid and their potential ecological risk.
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