具有直接Z型光催化机制的非金属BC4N/aza-CMP异质双层的光催化固氮性能

Direct Z-scheme photocatalytic nitrogen reduction to ammonia with water in metal-free BC4N/aza-CMP heterobilayer

我们设计了一种不含金属的二维双层异质结构BC_(4)N/aza-CMP,该体系可在水溶液中将N2分子通过光催化作用还原为氨.通过密度泛函理论和非绝热分子动力学方法,我们发现该异质结构中的光生载流子遵循直接Z型迁移机制.这将有效分离光生电荷并使氮还原反应和氧发生反应分别在BC_(4)N层和aza-CMP层上进行,实现反应位点的空间分离.值得一提的是,BC_(4)N上的B原子可以有效吸附N2分子并激活N≡N键,这将降低氮还原反应的过电势并促进随后的质子化进程,且该异质双层具有适宜的带隙和带边位置,能够有效吸收太阳光并提供充足的驱动力来触发氧化还原反应,实现无任何牺牲剂辅助的光催化氨合成.本工作将为直接Z型固氮光催化剂的设计提供重要借鉴,并促进太阳能驱动的氨合成的发展.

Photocatalytic ammonia(NH_(3))synthesis from air and water without external energy input or sacrificial agents is an attractive approach for nitrogen fixation.How-ever,finding a suitable photocatalyst with strong optical ab-sorption,efficient photogenerated carrier separation,and adequate driving force(potentials of photoinduced carriers)to trigger the nitrogen reduction reactions(NRRs)and oxygen evolution reactions(OERs)simultaneously is challenging.Herein,we propose a direct Z-scheme photocatalytic system based on a two-dimensional metal-free BC_(4)N/aza-CMP het-erobilayer.The results of density functional theory and time-dependent ab initio nonadiabatic molecular dynamics reveal that the photoexcited carriers in the BC_(4)N/aza-CMP hetero-bilayer follow a Z-scheme migration route,leading to the ef-ficient charge carrier separation and spatially separated reaction sites for NRR(BC_(4)N layer)and OER(aza-CMP layer).Moreover,the appropriate band gaps and energy levels of the BC_(4)N/aza-CMP heterobilayer enable efficient solar energy capture and provide sufficient driving force(1.01 V for NRR and 2.11 V for OER)to initiate the redox reactions.Ad-ditionally,the activation of the N≡N bond by B atoms in the BC_(4)N layer promotes the sequential hydrogenation of N atoms and reduces the overpotential of NRR.Consequently,the NRR and OER can proceed spontaneously,driven by photo-generated carriers with no need for sacrificial agents.The predicted maximum value of solar-to-chemical efficiency is 7.59%.This work will be an important reference for the ra-tional design of direct Z-scheme photocatalysts for NRR and promote the development of solar-driven NH_(3) synthesis.