 Electro-catalytic recycling of waste nitrate to NH3 under ambiured conditions may be an appealing alternative to the Haber-Bosch process. Here the authors report a tandem catalyst system involving cooperative adsorption of reaction intermediate on different transition metal active sites for nitrate electro-reduction with high efficiency. This article was authored by Wenhui He, Jian Zhong, Stefan Decofer and others.