Speaker
Description
The electrocatalytic reduction of nitrate (NO3RR) presents a promising approach for decentralized clean ammonia (NH3) production, while simultaneously mitigating environmental pollution caused by toxic and carcinogenic nitrate-laden wastewater.[1] Copper-based materials are attractive NO3RR catalysts due to their affordability and high NH3 selectivity.[2] However, the mismatch in adsorption between N-intermediates and active hydrogen (H) makes pure Cu catalysts achieve high selectivity only at higher overpotentials.[3] In this study, we show that doping Cu with Pd significantly enhances NH3 selectivity at lower overpotentials. Combining different in situ/operando characterization techniques and electrochemical analytical methods, we revealed that Pd doping increases electrochemical active surface area, accelerates the reduction of oxidized Cu to metallic Cu, and provides more accessible H. Furthermore, through the strategy of pulsed electrolysis, ammonia was obtained as the main product over a wide range of applied potential, starting at just 0.25 V vs. RHE (reversible hydrogen electrode). Notably, 10 consecutive catalyst recycling experiments exhibited negligible decay in Faradaic efficiency (>90%) and yield rate of ammonia. Such active and stable performance is attributed to the reversible transition between Cu(II) and Cu(0) during pulsed electrolysis, which facilitates the continuous regeneration of active species. This work not only achieves efficient and stable NH3 synthesis at low overpotentials, but also provides insights into the dynamic features and underlying mechanisms responsible for the improved performance.
