Research of Hydrogen Preparation with Catalytic Steam-Carbon Reaction Driven by Photo-Thermochemistry Process

An experiment of hydrogen preparation from steam-carbon reaction catalyzed by K2CO3 was carried out at 700°C, which was driven by the solar reaction system simulated with Xenon lamp. It can be found that the rate of reaction with catalyst is 10 times more than that without catalyst. However, for the catalytic reaction, there is no obvious change for the rate of hydrogen generation with catalyst content range from 10% to 20%. Besides, the conversion efficiency of solar energy to chemical energy is more than 13.1% over that by photovoltaic-electrolysis route. An analysis to the mechanism of catalytic steam-carbon reaction with K2CO3 is given, and an explanation to the nonbalanced [H2]/[CO + 2CO2] is presented, which is a phenomenon usually observed in experiment. 1. Introduction Hydrogen is an important energy material to fuel cell and various chemicals such as methanol, dimethyl ether, and synthetic gasoline. The traditional way to obtain hydrogen is to decompose the methane and water, which consumes a lot of other powers such as electricity. Therefore, the technical improvements to make hydrogen generation a cost-effective reality have become challenging subjects. The sunlight is an inexhaustible and cost-free source of energy. The direct use of solar energy to obtain hydrogen is the most desirable way that has drawn wide attention from energy scientists all over the world [1–4]. There were three ways in the past decades to produce hydrogen by solar energy: photovoltaic-electrolysis (PVE), photo-electrochemistry (PEC), and photo-thermochemistry (PTC). PVE makes use of solar cell to drive electrolysis of water, which is a way to directly convert solar energy into chemical energy [5]. Since the water electrolysis has been a mature technology, PVE process is maturer than the other two solar-to-hydrogen processes currently. The PEC makes use of electrochemical reactions [6–8] driven by quantum effects of photoirradiation on semiconductor metal oxide (SMO) catalytic anode which is connected to an external circuit. On the base of optical excitation, the excited electrons on SMO are removed from the anode to cathode through external circuit. The four holes were left in the catalytic anode of SMO, where the water can be split as follows. At cathode the is reduced: where is the reduction potential. The production of hydrogen by PTC uses concentrated solar radiation as the energy source to drive cycle redox reaction at more than 1500？K [9–11], such as the pyrogenation of and the oxidation of？？ ？？by turn. The energy conversion efficiency (ECE) of solar-to-hydrogen