Carbon Dots Supported on CuNi Layered Double Hydroxides as Electrocatalysts for Nitrate Reduction
Hongtao Sun, Dongxu Zhang, Yanhong Liu, Xiulian Yin, Qitao Chen, Mingze Liu, Long Zhang, Hui Huang, Wei Zhang, Zhenhui Kang, Baodong MaoAbstract
The electrochemical nitrate reduction reaction (NO3RR) offers a green alternate for ammonia (NH3) synthesis, which is still hindered by the low Faradaic efficiency (FE) and undesired nitrite release, especially upon fluctuating operating conditions. Here, we demonstrate a carbon dot (CD)-coupled CuNi layered double hydroxide (CuNi LDH) interfacial 2D nanoreactor for efficient nitrate reduction with high selectivity and low nitrite (NO2−) release resilient to wide fluctuations owing to the specific stabilization and directional conversion of *NO2 within the confined interfacial catalytic microenvironment. The intimate coupling between CuNi LDH/CDs enables effective interfacial potential accumulation and charge redistribution, which induces a positive shift of nitrate activation to 0 V vs. RHE and selective stabilization of *NO2 that fundamentally avoids the immature release of NO2−. In situ spectroscopy and DFT calculations reveal the facilitated *NO3 to *NO2 conversion and the lowered barrier for *NH2OH to *NH2 (the rate-determining step). The optimized CuNi LDH/CDs in the flow cell maintain NH3 FEs above 90% and NO2− residue below 10 ppm over varying potentials, nitrate concentrations, and synthetic simulated industrial wastewater temperatures. This work provides a reliable catalytic system for practical NO3RR that is resilient to fluctuations and a revolutionizing strategic paradigm for catalyst design in complex environmental catalysis.