Au nanoclusters anchored on TiO2 nanosheets for high-efficiency electroreduction of nitrate to ammonia

Electrocatalytic nitrate reduction reaction (NO3RR) offers a unique rationale for green NH3 synthesis, yet the lack of high-efficiency NO3RR catalysts remains a great challenge. In this work, we show that Au nanoclusters anchored on TiO2 nanosheets can efficiently catalyze the conversion of NO3RR-to-NH3 under ambient conditions, achieving a maximal Faradic efficiency of 91%, a peak yield rate of 1923 µg·h−1·mgcat.−1, and high durability over 10 consecutive cycles, all of which are comparable to the recently reported metrics (including transition metal and noble metal-based catalysts) and exceed those of pristine TiO2. Moreover, a galvanic Zn-nitrate battery using the catalyst as the cathode was proposed, which shows a power density of 3.62 mW·cm−2 and a yield rate of 452 µg·h−1·mgcat.−1. Theoretical simulations further indicate that the atomically dispersed Au clusters can promote the adsorption and activation of NO3− species, and reduce the NO3RR-to-NH3 barrier, thus leading to an accelerated cathodic reaction. This work highlights the importance of metal clusters for the NH3 electrosynthesis and nitrate removal.