Selective Electroreduction of Nitrate into Ammonia on CuCoAl Layered Double Hydroxide for Sustainable Resourcification

One-step nitrate electroreduction (NO3RR) is a promising strategy to generate ammonia in a straightforward and environmentally friendly manner. However, most catalysts suffer from limited electrocatalytic activity as well as poor selectivity. In this work, a tunable trimetallic CuCoAl layered double hydroxide (LDH) catalyst was designed to generate ammonia exclusively and efficiently with an onset potential at 0.13 V vs. RHE. The synergy among Cu, Co, and Al bestowed a 99.5 % Faradaic efficiency (FE) for ammonia with a yield rate of 0.22 mol h-1 g-1, rivaling the performance of state-of-the-art non-precious metal NO3RR electrocatalysts. Control materials were employed to elucidate the roles of Cu, Co, and Al toward lowering the overpotential and suppressing the formation of nitrite byproduct. DFT calculations were performed to further investigate the adsorption strength of anionic adducts and electrolytes on LDH surface to unravel the effects of buffer conditions on NO3RR performance. The scalable nature of our earth-abundant catalysts is particularly attractive due to the intrinsic low costs of the raw materials. We envision that this precious-metal-free catalyst can be generally applicable to other resourcification processes to achieve a future sustainable society.