Professor Hu Zheng, a member of Key Laboratory of Mesoscopic Chemistry of Ministry of Education, has made an important progress in the research of convenient construction, mechanism and performance of single site catalysts. The paper entitled the simple construction of single site catalysts by the synergy of micropore trapping and nitrogen anchoring was published in nature communications (2019, 10, 1657). The experimental work was mainly performed by Zhang Zhiqi, Ph.D., Chen Yugang, M.A., and Zhou Liqi, Ph.D. The corresponding authors are Professor Wu Qiang, Professor Hu Zheng from School of chemistry and chemical engineering, and Professor Wang Peng from School of Modern Engineering and Applied Sciences, Nanjing University.
Single site catalyst (often referred as single atom catalyst in the literature) is the limit of supported catalyst. Because of its maximum atom utilization, unique catalytic performance, uniform coordination environment and other characteristics, it has become the forefront of scientific research in recent years. Due to the high surface energy and easy agglomeration, the preparation if single site catalysts is usually complex. Therefore, it is of great significance to construct single site catalysts with high stability for the related basic or applied research.
Professor Hu’s research group, ‘Physical Chemistry for Energy NanoMaterials’, has made a series of important progresses in the research on the growth mechanism, material design, energy conversion/storage function and regulation mechanism of nano/mesoscopic structure for a long time. In recent years, they have developed a technical route for new carbon based nanocage materials with novel mesoscopic structure, high specific surface area, coexistence of micro, meso and macro pores, easy doping and regulating, which demonstrated a series of excellent energy conversion and storage capabilities [see: Acc. Chem. Res. 50(2017)435; Adv. mater. 24(2012)347, 24(2012)5593, 27(2015)3541, 29(2017)1604569, 29(2017)1700470，31(2019)1804799；ACS Catal. 5(2015)1857, 5(2015)6707, 8(2018)8477; Nano Energy 12(2015)657, 57(2019)34; Science Bulletin 62(2017)1365]。
In this study, they used the nitrogen doped carbon nanocage (hNCNC) as the support. The single atom sites were constructed by using the abundant micropores (~ 0.6nm) on the cage wall to easily capture metal coordination anions, and the nitrogen dopants to facilitate the anchoring of metal atoms. Through the simple impregnation, adsorption and drying (70 ℃) process, M1/hNCNC (M = Pt, Pd, Au, Ir, etc.) single atom precious metal catalysts were prepared. Pt loading of Pt1/hNCNC catalyst can be up to 5.68 wt%, showing extremely low hydrogen evolution overpotential, ultra-high mass activity and excellent stability in acid medium (Fig. 1). The formation mechanism of Pt single site catalyst and the origin of its excellent stability were revealed through theoretical and experimental studies. The synergistic effect of micropore capture and heteroatom anchoring revealed in this study provides a new idea and method for the construction of highly stable single atom catalyst, which is of great value for promoting the basic research and practical application of single site catalyst.
The research was supported by key projects of NSFC and National Key Research and Development Program from the Ministry of science and technology.
Figure 1. Morphology and hydrogen evolution performance of Pt single site catalyst. (a) Photos of HAADF-STEM; (b) EXAFS map; (c) hydrogen evolution activity; (d) stability.