Photoelectrochemical reduction of nitrates with visible light by nanoporous Si photoelectrode

The reduction of nitrate into nitrite is a rate limit reaction step for the whole nitrate reduction reaction. Photoelectrochemical nitrate reduction using visible light active photoelectrode has the advantage of high activity and usage of renewable solar energy. Here we demonstrate that the nanoporous p-Si photoelectrode is a promising candidate for visible light photoelectrochemical nitrate reduction. The regular planar p-Si photoelectrode without co-catalysts exhibits low activity for photoelectrochemical nitrate reduction with a very low faraday efficiency. Interestingly, the nanoporous p-Si photoelectrodes fabricated from the planar Si exhibits high performance for photoelectrochemical nitrate reduction with both high photocurrent and high faraday efficiency for nitrate reduction. The effects of solution pH and nitrate concentration on photoelectrochemical nitration reduction by nanoporous Si photoelectrode were investigated and discussed. In all, the reaction of nitrate reduction into nitrite process can be efficiently promoted by nanoporous Si electrode under the illumination of visible light, exhibiting over 80% faraday efficiency.