碳层网络促进Sn/SnO_(2)纳米颗粒选择性CO_(2)还原

Selective CO_(2) Reduction to Formate on Heterostructured Sn/SnO_(2) Nanoparticles Promoted by Carbon Layer Networks

在各类CO_(2)还原电催化剂中,锡基材料获得了研究人员的广泛关注,但其总体催化性能仍然受催化剂电极的组成,形貌和结构的限制。在本研究中,我们利用Sn低熔点(m.p.232℃)的特性,在聚多巴胺碳化的同时实现Sn的熔化与再结晶,合成了由氮掺杂碳层网络分散的异质结构Sn/SnO_(2)纳米颗粒自支撑电极(Sn/SnO_(2)@NC)。氮掺杂碳层网络有利于电子的富集,可提高催化剂电极的导电性,防止超细纳米粒子的团聚,并保护其不在电解液中溶解。在CO_(2)饱和的0.5 mol·L^(-1) NaHCO_(3)水溶液中,所制备Sn/SnO_(2)@NC电极与没有碳层网络包覆的电极相比,其CO_(2)还原催化性能得到了很大的提高。该Sn/SnO_(2)@NC电极在-0.9 V(vs.RHE)的电解电压下,电流密度为17 mA·cm^(-2),甲酸盐产物的选择性为83%。通过偶联该CO_(2)还原催化电极与商品化RuO2催化剂作为水氧化阳极,可实现持续的CO_(2)/H_(2)O电解。此外,以Sn/SnO_(2)@NC为阴极,Zn箔为阳极,我们还构建了可充放电的水系Zn-CO_(2)电池。该电池的输出开路电压为1.35 V,峰值功率密度为0.9 mW·cm^(-2)。本研究为高性能CO_(2)还原催化剂的设计提供了新的思路,同时可充放电Zn-CO_(2)电池的构建为绿色能源转换和存储系统提供了新的方案。

Tin(Sn)-based materials have emerged as promising electrocatalysts for selective reduction of CO_(2) to formate,but their overall performances are still limited by electrode structures which govern the accessibility to active sites,the electron transfer kinetics,and the catalytic stability.In this study,the heterostructured Sn/SnO_(2) nanoparticles dispersed by N-doped carbon layer networks(Sn/SnO_(2)@NC)were synthesized by a melt-recrystallization method taking the low melting point of Sn(m.p.232℃).The N-doped carbon layer networks derived from polydopamine could attract more electrons on the electrocatalyst,serve as conductive agents and protect the ultrafine nanoparticles from agglomeration and dissolution.The Sn/SnO_(2)@NC electrode exhibited the greatly enhanced performance for CO_(2) reduction to formate in CO_(2)-saturated 0.5 mol·L^(-1) aqueous NaHCO_(3) solution,showing a selectivity of 83%at only-0.9 V vs.RHE with a sustained current density of 17 mA·cm^(-2) for extended periods.By coupling the catalytic electrode with a commercially available RuO2 catalyst as the anode,the long-term CO_(2)/H_(2)O splitting has been achieved.Furthermore,a rechargeable aqueous Zn-CO_(2) battery with Sn/SnO_(2)@NC as the cathode and Zn foil as the anode was constructed.It could output electric energy with an open circuit voltage of 1.35 V and a peak power density of 0.9 mW·cm^(-2).