Electricity chemical energy conversion

The are two possibilities, the direct solar into electricity conversion (photovoltaic) and the solar into chemical energy conversion (solar fuels), e.g., the production of H2 by water splitting or the photocatalytic conversion of C02 into chemi-... 

These cells operate under illumination in combination with a bias, which serves to either drive electrolytic reactions for which the photon energy is insufficient or to increase the rate of chemical energy conversion by reducing electron-hole recombination in the semiconductor bulk. Most commonly an electrical bias is provided to drive the reactions [36-41]. 

These data underline the enormous dimension of photosynthesis and the biosphere for energy conversion. From these figures, it could appear that there is no need for any artificial chemical energy conversion as there is abundant natural energy conversion. Humankind only bums 4.5% of the annual photosynthesis fixation of carbon. If we convert this into annual electrical energy equivalents, we arrive for photosynthesis at about 250 TW and for total human consumption at about 15 TW. In this argument, we first have to add the electrical equivalent of our food energy that is and... 

The overall energy conversion efficiency for the complete process of mathanol chemical energy conversion dc electric energy will be similar (43%) for a system with an RAFC operating at 0.70 V and a DMFC operating at 0.55 V, provided the fuel efficiency in the DMFC is raised to 90% (the latter requirement could be possibly achieved by combination of anodic effects and membrane modification). 

PEC cells for solar-to-electrical energy conversion PEC cells for solar-to-chemical energy conversion Semiconductor dispersions for providing cleaner environments Concluding remarks References... 

In the 1970s, the idea of photoelectrochemical cells for light to electrical and/or chemical energy conversion attracted scientists in various fields as a novel energy conversion device. Photoetching has been widely used to modify the semiconductor surface and consequently improve the cell efficiency [1, 2]. This improvement is attributed to several effects, such as a decrease in reflection losses (3), an increase in effective electrode area, a removal of surface defects acting as recombination centers [4-7], and change in the chemical composition of surface [8, 9j. 

Fuel Cell Catalysts. Euel cells (qv) are electrochemical devices that convert the chemical energy of a fuel direcdy into electrical and thermal energy. The fuel cell, an environmentally clean method of power generation (qv), is more efficient than most other energy conversion systems. The main by-product is pure water. 

Cogeneration is an energy conversion process wherein heat from a fuel is simultaneously converted to useful thermal energy (e.g., process steam) and electric energy. The need for either form can be the primary incentive for cogeneration, but there must be opportunity for economic captive use or sale of the other. In a chemical plant the need for process and other heating steam is hkely to be the primaiy in a pubhc utility plant, electricity is the usual primary produc t. 

In some instances, however, pai t of the chemical energy bound in relatively high-enthalpy compounds can be converted directly to electricity as these reactants are converted to produc ts of lower enthalpy (galvanic action). A process in the opposite direc tion also is possible for some systems an elec tric current can be absorbed as the increased chemical energy of the higher-enthalpy compounds (electrolytic action). The devices in which electrochemical energy conversion processes occur are called cells. 

A fuel cell is equivalent to a generator it converts a fuel s chemical energy directly into electricity. The main difference between these energy conversion devices is that the fuel cell acccomplishes this directly, "without the two additional intermediate steps, heat release and mechanical motion. 

An electrochemical cell is a device by means of which the enthalpy (or heat content) of a spontaneous chemical reaction is converted into electrical energy conversely, an electrolytic cell is a device in which electrical energy is used to bring about a chemical change with a consequent increase in the enthalpy of the system. Both types of cells are characterised by the fact that during their operation charge transfer takes place at one electrode in a direction that leads to the oxidation of either the electrode or of a species in solution, whilst the converse process of reduction occurs at the other electrode. 

One of the most well-known electrochemical cells that is used for the conversion of chemical energy into electrical energy is the Daniell cell... 

Electrochemistry is the study of the interconversion of electrical and chemical energy. This conversion takes place in an electrochemical cell that may be a(n)—... 

Fuel Cells The Next Step in Chemical- to Electrical-Energy Conversion ... 

Fuel cells have attracted considerable interest because of their potential for efficient conversion of the energy (AG) from a chemical reaction to electrical energy (AE). This efficiency is achieved by directly converting chemical energy to electricity. Conventional systems burn fuel in an engine and convert the resulting mechanical output to electrical power. Potential applications include stationary multi-megawatt power plants, battery replacements for personal electronics, and even fuel-cell-powered unmanned autonomous vehicles (UAVs). 

Electron-transfer reactions occur all around us. Objects made of iron become coated with mst when they are exposed to moist air. Animals obtain energy from the reaction of carbohydrates with oxygen to form carbon dioxide and water. Turning on a flashlight generates a current of electricity from a chemical reaction in the batteries. In an aluminum refinery, huge quantities of electricity drive the conversion of aluminum oxide into aluminum metal. These different chemical processes share one common feature Each is an oxidation-reduction reaction, commonly called a redox reaction, in which electrons are transferred from one chemical species to another. 

The membrane-separated reductant and oxidant formed upon PET can be used for accomplishment of various catalytic redox reactions which provide conversion of the chemical energy of a (D. ..A ) pair into the chemical energy of a pair of more stable species such, e.g., as H2 and O2 molecules. This stored energy can be released when necessary in the form of high potential heat or electricity via combustion of H2 + 1/2 O2 mixture in a furnace or fuel cell. 

Davtyan, O. K., The Problem of Direct Conversion of the Chemical Energy of Fuels into Electrical Energy [in Russian], Rublishing House of the USSR Academy of Sciences, Moscow, 1947. 

The following two papers deal mainly with problems in energy conversion, in piarticular, the transformation of irradiation energy into electrical or chemical energy. The present status and future possible developments of photoelectrochemical energy conversion is presented. In a second paper electrochemical developments are connected to colloidal chemistry and the application of colloidal particles as catalysts for electron transfer reactions and as photocatalysts are discussed. 

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