Novel design of single transition metal atoms anchored on C6N6 nanosheet for electrochemical and photochemical N2 reduction to Ammonia

Abstract

The development of environmentally benign, cost-effective, efficient electrocatalyst for N2 reduction into NH3 formation under ambient condition is the most challenging task. On the other hand, photocatalysis plays a vital role to convert solar energy into valuable chemicals. As a polymeric semiconductor, triazine based porous C6N6 sheet can behave as next generation photocatalyst due to its appealing band structure, mechanical as well as thermodynamical stability. In nature the only biological enzyme is nitrogenase which can undergo N2 fixation with its Fe-Mo active center. Inspired by this, with the assistance of Density Functional Theory, the electrocatalytic as well as photocatalytic activity are investigated for a series of total 13 transition metal (including Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ru, Rh, Pd) embedded on C6N6 sheet towards NRR. Through high-throughput first-principle calculations, Mo@C6N6 sheet for NRR is screened out, which shows high catalytic activity and selectivity towards NRR. We found that NRR is favorable in Distal Pathway with a limiting potential value of 0.53 V which is quite well. Moreover, our predicted catalyst Mo@C6N6 sheet is capable to harvest solar light which is clear from the satisfactory absorption zone, suitable band edge positions and enough electron-hole separation. So, precisely it can be stated that, this system can be used as promising electrocatalyst as well as efficient photocatalyst for NRR. Next, the bond-length and charge variation of all the intermediates participated in each elementary step are further examined to obtain deep insights of high catalytic activity. The formation energy, lower binding energy and AIMD simulation at various temperature (300, 500 and 800 K) indicate its thermodynamic stability and it strengthens the ease of experimental synthesis. These findings provide a beneficial platform for exploring new electrocatalyst and photocatalyst for NRR under ambient conditions.