Electrochemical synthesis of ammonia by nitrate reduction on indium incorporated in sulfur doped graphene

Nitrate contaminant in groundwater has become a global problem. As a nitrogen-containing source, catalyzing nitrate to ammonia by electrochemical conversion draws promising blueprint from the perspective of solving energy crisis and environment pollution. Here we report a sulfur doped graphene with indium confined for nitrate reduction. The catalyst exhibits an ammonia production of 220 mmol gcat-1h−1 and a Faradaic efficiency of about 75% at −0.5 V vs reversible hydrogen electrode (RHE). The experimental results combined with density functional theory (DFT) calculations demonstrate that the abundant active sites afforded by S doped graphene and hybrid electronic structure of In species in catalyst account for predominant nitrate reduction and suppression of hydrogen evolution reaction. This work can offer an electronic structure design strategy for other energy related applications.