The modulating effect of N coordination on single-atom catalysts researched by Pt-Nx-C model through both experimental study and DFT simulation

doi:10.1016/j.jmst.2021.01.093

Abstract

Abstract:

N-doped carbon-based single-atom catalysts (NC-SACs) are widely researched in various electrochemical reactions due to high metal atom utilization and catalytic activity. The catalytic activity of NC-SACs originates from the coordinating structure between single metal site (M) and the doped nitrogen (N) in carbon matrix by forming M-Nx-C structure (1≤ x≤ 4). The M-N4-C structure is widely considered to be the most stable and effective catalytic site. However, there is no in-depth research for the “x” modulation in Pt-Nx-C structure and the corresponding catalytic properties. Herein, atomically dispersed Pt on N-doped carbon (Pt-NC) with Pt-Nx-C structure (1≤ x≤ 4), as a research model, is fabricated by a ZIF-8 template and applied to catalytic oxygen reduction. Different carbonization temperatures are used to control N loss, and then modulate the N coordination of Pt-Nx-C structure. The Pt-NC has the predictable low half-wave potential (E1/2) of 0.72 V vs RHE compared to the Pt/C 20% of 0.81V due to low Pt content. Remarkably, the Pt-NC shows a high onset potential (1.10 V vs RHE, determined for j = -0.1 mA cm2) and a high current density of 5.2 mA cm-2, more positive and higher than that of Pt/C 20% (0.96 V) and 4.9 mA cm-2, respectively. As the structural characterization and DFT simulation confirmed, the reducing Pt-N coordination number induces low valence of Pt atoms and low free energy of oxygen reduction, which is responsible for the improved catalytic activity. Furthermore, the Pt-NC shows high mass activity (172 times higher than that of Pt/C 20%), better stability and methanol crossover resistance.

Key words: Modulating effect, N coordination, Single-atom catalysts, Pt-N_x-C model, DFT simulation

Mengmeng Fan, Jiewu Cui, Junjie Zhang, Jingjie Wu, Shuangming Chen, Li Song, Zixing Wang, Ao Wang, Robert Vajtai, Yucheng Wu, Pulickel M. Ajayan, Jianchun Jiang, Dongping Sun. The modulating effect of N coordination on single-atom catalysts researched by Pt-N_x-C model through both experimental study and DFT simulation[J]. J. Mater. Sci. Technol., 2021, 91: 160-167.

Figures/Tables 7

Fig. 1. (a) Schematic illustration for fabricating Pt-NC. SEM images of Pt2+/ZIF-8-1.5% without calcination (b) and Pt-NC-1.5% calcined at 1100°C for 1 h (c), bar 200 nm. (d) N2 adsorption desorption isotherms of NC, Pt-NC calcined at 1100°C for 1 h (Inset is the pore diameter distribution curves). (e, f) Aberration-corrected HAADF-STEM images of Pt-NC-1.5% calcined at 1100°C for 1 h, bar 100 nm and 10 nm. (g) EDS spectra selecting different sites at HAADF-STEM images. (h, i) High-resolution HADDF-STEM image and corresponding enlarged view of Pt-NC-1.5% (calcined at 1100°C for 1 h) with abundant bright dots, bar 100 nm and 2 nm.

Fig. 2. (a) XPS survey scans for the NC, Pt-NC-1.5% and Pt-NC-2.0%. (b) The high-resolution N 1s spectra of NC, Pt-NC-1.5%. (c) The high-resolution N 1s of Pt-NC-1.5% samples under different calcination temperatures at 800-1100°C. (d) The contents of N configurations in the Pt-NC-1.5% samples at various temperatures. (e) The high-resolution Pt 4f of the Pt-NC-1.5%, -2.0%. (f) The Raman spectra of the Pt-NC-1.5% samples at different calcination temperatures.

Table 1 The content of N species (at.%) in the Pt-NC-1.5% samples at various calcination temperatures.

Temperatue	Pyridinic N	Pt-N	Pyrollic/graphitic N	Zn-N
800°C	2.90	3.20	11.90	1.92
900°C	3.00	3.30	9.60	0.59
1000°C	0.71	0.84	4.65	/
1100°C	0.40	0.57	3.13	/

Fig. 3. (a) CV curves of NC, Pt-NC-1.5%, -2.0% and Pt/C (20%) in N2- or O2-saturated 0.1 M KOH with a sweep rate of 100 mV s-1. (b) RDE polarization curves of Pt-NC-1.5% samples under different calcination temperatures in O2-saturated 0.1 M KOH with a sweep rate of 10 mV s-1 and rotation rate of 1600 rpm. (c) LSV curves in O2-saturated 0.1 M KOH aqueous solution with a sweep rate of 10 mV s-1 and rotation rate of 1600 rpm. (d) LSV curves of Pt-NC-1.5% in O2 saturated 0.1 M KOH at various rotation rates (Inset is K-L plots from 0.1 to 0.4 V vs RHE). (e) H2O2% yield of the samples during the LSV test (solid line) and the corresponding calculated electron transfer number (dashed line) with 10 mV s-1 at 1600 rpm in 0.1 M KOH.

Fig. 4. (a) Tafel plots from LSV curves of Pt-NC-1.5%, Pt/C (20%). (b) Current density and mass activity at 0.70 V vs RHE of Pt-NC-1.5%, Pt-NC-2.0% and Pt/C (20%) for ORR. (c) Chronoamperometric curves for stability test with the Pt-NC-1.5% and Pt/C (20%) at 0.56 V for 8000 s in 0.1M KOH. (d) Methanol toxicity test with Pt-NC-1.5% and Pt/C (20%) at 0.56 V in 0.1 M KOH (1 M methanol was added into solution at 400 s).

Fig. 5. The simulated structures of (a) Pt-N1-C, (b) Pt-N2-C, (c) Pt-N3-C, (d) Pt-N4-C with different Pt-N coordination.

Fig. 6. The proposed reaction pathways for reducing O2 to H2O on Pt-N1-C catalyst in acidic environment and the free energy diagrams on different Pt-Nx-C catalysts (Inset).

References 66

[1]	C. Zhu, S. Fu, Q. Shi, D. Du, Y. Lin, Angew. Chem. Int. Ed. 56(2017) 13944-13960.
[2]	A. Wang, J. Li, T. Zhang, Nat. Rev. Chem. 2(2018) 65-81.
[3]	Y. Huang, X. Huang, M. Ma, C. Hu, F. Seidi, S. Yin, H. Xiao, J. Mater. Chem. C 9 (2021) 818-828.
[4]	Y. Huang, A. Buffa, H. Deng, S. Sarkar, Y. Ouyang, X. Jiao, Q. Hao, D. Mandler, J. Power Sources 439 (2019) 227046.
[5]	M. Fan, J. Cui, J. Wu, R. Vajtai, D. Sun, P.M. Ajayan, Small 16 (2020) 1906782.
[6]	B. Bayatsarmadi, Y. Zheng, A. Vasileff, S.Z. Qiao, Small 13 (2017) 1700191.
[7]	H. Han, Y. Noh, Y. Kim, S. Park, W. Yoon, D. Jang, S.M. Choi, Green Chem. 22(2020) 71-84.
[8]	H. Wu, Y. Cheng, B. Wang, Y. Wang, M. Wu, W. Li, B. Liu, S. Lu. J. Energy Chem. 57(2021) 198-205.
[9]	W. Li, Y. Zhao, Y. Liu, M. Sun, G.I.N. Waterhouse, B. Huang, K. Zhang, T. Zhang, S. Lu, Angew. Chem. Int. Ed. 60(2020) 3290-3298.
[10]	Z. Lin, G.H. Waller, Y. Liu, M. Liu, C.P. Wong, Nano Energy 2 (2013) 241-248.
[11]	H. Han, S. Park, D. Jang, S. Lee, W.B. Kim, Chem. Sus. Chem. 13(2020) 539-547.
[12]	H. Han, Y. Noh, Y. Kim, W.S. Jung, S. Park, W.B. Kim, Nanoscale 11 (2019) 2423-2433.
[13]	H. Song, Y. Li, L. Shang, Z. Tang, T. Zhang, S. Lu, Nano Energy 72 (2020) 104730.
[14]	Y. Liu, X. Li, Q. Zhang, W. Li, Y. Xie, H. Liu, L. Shang, Z. Liu, Z. Chen, L. Gu, Z. Tang, T. Zhang, S. Lu, Angew. Chem. Int. Ed. 59(2020) 1718-1726.
[15]	X. Li, W. Bi, M. Chen, Y. Sun, H. Ju, W. Yan, J. Zhu, X. Wu, W. Chu, C. Wu, Y. Xie. J. Am. Chem. Soc. 139(2017) 14889-14892.
[16]	S. Wei, A. Li, J.C. Liu, Z. Li, W. Chen, Y. Gong, Q. Zhang, W.C. Cheong, Y. Wang, L. Zheng, H. Xiao, C. Chen, D. Wang, Q. Peng, L. Gu, X. Han, J. Li, Y. Li, Nat. Nanotechnol. 13(2018) 856-861.
[17]	C. Zhang, S. Yang, J. Wu, M. Liu, S. Yazdi, M. Ren, J. Sha, J. Zhong, K. Nie, A.S. Jalilov, Z. Li, H. Li, B.I. Yakobson, Q. Wu, E. Ringe, H. Xu, P.M. Ajayan, J.M. Tour, Adv. Energy Mater. 8(2018) 1703487.
[18]	Y. Pan, Y. Chen, K. Wu, Z. Chen, S. Liu, X. Cao, W.C. Cheong, T. Meng, J. Luo, L. Zheng, C. Liu, D. Wang, Q. Peng, J. Li, Chen C, Nat. Commun. 10(2019) 4290.
[19]	J. Li, S. Chen, N. Yang, M. Deng, S. Ibraheem, J. Deng, J. Li, L. Li, Z. Wei, Angew. Chem. Int. Ed. 58(2019) 7035-7039.
[20]	E. Luo, H. Zhang, X. Wang, L. Gao, L. Gong, T. Zhao, Z. Jin, J. Ge, Z. Jiang, C. Liu, W. Xing, Angew. Chem. Int. Ed. 58(2019) 12469-12475.
[21]	S. Zhou, L. Shang, Y. Zhao, R. Shi, G.I.N. Waterhouse, Y.C. Huang, L. Zheng, T. Zhang, Adv. Mater. 31(2019) 1900509.
[22]	Y.N. Gong, L. Jiao, Y. Qian, C.Y. Pan, L. Zheng, X. Cai, B. Liu, S.H. Yu, H.L. Jiang, Angew. Chem. Int. Ed. 59(2020) 2705-2709.
[23]	F. Li, Y. Bu, G.F. Han, H.J. Noh, S.J. Kim, I. Ahmad, Y. Lu, P. Zhang, H.Y. Jeong, Z. Fu, Q. Zhong, J.B. Bae, Nat. Commun. 10(2019) 2623.
[24]	J. Li, H. Zhang, W. Samarakoon, W. Shan, D.A. Cullen, S. Karakalos, M. Chen, D. Gu, K.L. More, G. Wang, Z. Feng, Z. Wang, G. Wu, Angew. Chem. Int. Ed. 58(2019) 18971-18980.
[25]	T. Li, J. Liu, Y. Song, F. Wang, ACS Catal. 8(2018) 8450-8458.
[26]	D. Liu, X. Li, S. Chen, H. Yan, C. Wang, C. Wu, Y.A. Haleem, S. Duan, J. Lu, B. Ge, P.M. Ajayan, Y. Luo, J. Jiang, L. Song, Nat. Energy 4 (2019) 512-518.
[27]	X. Zhao, M. Yin, L. Ma, L. Liang, C. Liu, J. Liao, T. Lu, W. Xing, Energ Environ. Sci. 4(2011) 2736-2753.
[28]	X. Cui, S. Yang, X. Yan, J. Leng, S. Shuang, P.M. Ajayanl, Z. Zhang, Adv. Funct. Mater. 26(2016) 5708-5717.
[29]	S. Wang, S.P. Jiang, T.J. White, J. Guo, X. Wang, J. Phys. Chem. C 113 (2009) 18935-18945.
[30]	X. Hai, X. Zhao, N. Guo, C. Yao, C. Chen, W. Liu, Y. Du, H. Yan, J. Li, Z. Chen, X. Li, Z. Li, H. Xu, P. Lyu, J. Zhang, M. Lin, C. Su, S.J. Pennycook, C. Zhang, S. Xi, J. Lu, ACS Catal. 10(2020) 5862-5870.
[31]	X. Wang, Z. Chen, X. Zhao, T. Yao, W. Chen, R. You, C. Zhao, G. Wu, J. Wang, W. Huang, J. Yang, X. Hong, S. Wei, Y. Wu, Y. Li, Angew. Chem. Int. Ed. 57(2017) 1944-1948.
[32]	J. Jones, H. Xiong, A.T. DeLaRiva, E.J. Peterson, H. Pham, S.R. Challa, G. Qi, S. Oh, M.H. Wiebenga, X.I. Pereira Hernández, Y. Wang, A.K. Datye, Science 353 (2016) 150.
[33]	H. Zhang, S. Hwang, M. Wang, Z. Feng, S. Karakalos, L. Luo, Z. Qiao, X. Xie, C. Wang, D. Su, Y. Shao, G. Wu. J. Am. Chem. Soc. 139(2017) 14143-14149.
[34]	S.M. Unni, V.M. Dhavale, V.K. Pillai, S. Kurungot, J. Phys. Chem. C 114 (2010) 14654-14661.
[35]	R. Liu, D. Wu, X. Feng, K. Müllen, Angew. Chem. Int. Ed. 49(2010) 2565-2569.
[36]	S. Yang, X. Feng, X. Wang, K. Müllen, Angew. Chem. Int. Ed. 50(2011) 5339-5343.
[37]	C. Zhang, J. Sha, H. Fei, M. Liu, S. Yazdi, J. Zhang, Q. Zhong, X. Zou, N. Zhao, H. Yu, Z. Jiang, E. Ringe, B.I. Yakobson, J. Dong, D. Chen, J.M. Tour, ACS Nano 11 (2017) 6930-6941.
[38]	G. Kresse, J. Furthmüller, Phys. Rev. B 54 (1996) 11169-11186.
[39]	G. Kresse, D. Joubert, Phys. Rev. B 59 (1999) 1758-1775.
[40]	D. Deng, L. Yu, X. Pan, S. Wang, X. Chen, P. Hu, L. Sun, X. Bao, Chem. Commun. 47(2011) 10016-10018.
[41]	Y. Chen, S. Ji, W. Sun, W. Chen, J. Dong, J. Wen, J. Zhang, Z. Li, L. Zheng, C. Chen, Q. Peng, D. Wang, Y. Li. J. Am. Chem. Soc. 140(2018) 7407-7410.
[42]	Z. Liang, C. Qu, D. Xia, R. Zou, Q. Xu, Angew. Chem. Int. Ed. 57(2018) 9604-9633.
[43]	I. Kone, A. Xie, Y. Tang, Y. Chen, J. Liu, Y. Chen, Y. Sun, X. Yang, P. Wan, ACS Appl. Mater. Inter. 9(2017) 20963-20973.
[44]	L. Yang, X. Zeng, W. Wang, D. Cao, Adv. Funct. Mater. 28(2017) 1704537.
[45]	H. Zhang, H. Osgood, X. Xie, Y. Shao, G. Wu, Nano Energy 31 (2017) 331-350.
[46]	X. Wang, H. Zhang, H. Lin, S. Gupta, C. Wang, Z. Tao, H. Fu, T. Wang, J. Zheng, G. Wu, X. Li, Nano Energy 25 (2016) 110-119.
[47]	R. Ning, C. Ge, Q. Liu, J. Tian, A.M. Asiri, K.A. Alamry, C.M. Li, X. Sun, Carbon 78 (2014) 60-69.
[48]	H. Fei, J. Dong, M.J. Arellano-Jiménez, G. Ye, N. Dong Kim, E.L.G. Samuel, Z. Peng, Z. Zhu, F. Qin, J. Bao, M.J. Yacaman, P.M. Ajayan, D. Chen, J.M. Tour , Nat. Commun. 6(2015) 8668.
[49]	J. Liu, M. Jiao, L. Lu, H.M. Barkholtz, Y. Li, Y. Wang, L. Jiang, Z. Wu, D.J. Liu, L. Zhuang, C. Ma, J. Zeng, B. Zhang, D. Su, P. Song, W. Xing, W. Xu, Y. Wang, Z. Jiang, G. Sun, Nat. Commun. 8(2017) 15938.
[50]	T. Sun, L. Xu, D. Wang, Y. Li, Nano Res. 12(2019) 2067-2080.
[51]	M. Xiao, J. Zhu, G. Li, N. Li, S. Li, Z.P. Cano, L. Ma, P. Cui, P. Xu, G. Jiang, H. Jin, S. Wang, T. Wu, J. Lu, A. Yu, D. Su, Z. Chen, Angew. Chem. Int. Ed. 58(2019) 9640-9645.
[52]	F. Cao, L. Zhang, Y. You, L. Zheng, J. Ren, X. Qu, Angew. Chem. Int. Ed. 59(2020) 5108-5115.
[53]	Y. Chen, S. Ji, Y. Wang, J. Dong, W. Chen, Z. Li, R. Shen, L. Zheng, Z. Zhuang, D. Wang, Y. Li, Angew. Chem. Int. Ed. 56(2017) 6937-6941.
[54]	Y. Han, Z. Wang, R. Xu, W. Zhang, W. Chen, L. Zheng, J. Zhang, J. Luo, K. Wu, Y. Zhu, C. Chen, Q. Peng, Q. Liu, P. Hu, D. Wang, Y. Li, Angew. Chem. Int. Ed. 57(2018) 11262-11266.
[55]	D. Zhang, W. Chen, Z. Li, Y. Chen, L. Zheng, Y. Gong, Q. Li, R. Shen, Y. Han, W.C. Cheong, L. Gu, Y. Li, Chem. Commun. 54(2018) 4274-4277.
[56]	Z. Zhang, J. Xiao, X.J. Chen, S. Yu, L. Yu, R. Si, Y. Wang, S. Wang, X. Meng, Y. Wang, Z.Q. Tian, D. Deng, Angew. Chem. Int. Ed. 57(2018) 16339-16342.
[57]	Y. Chen, S. Ji, W. Sun, Y. Lei, Q. Wang, A. Li, W. Chen, G. Zhou, Z. Zhang, Y. Wang, L. Zheng, Q. Zhang, L. Gu, X. Han, D. Wang, Y. Li, Angew. Chem. Int. Ed. 59(2020) 1295-1301.
[58]	Y. Qu, B. Chen, Z. Li, X. Duan, L. Wang, Y. Lin, T. Yuan, F. Zhou, Y. Hu, Z. Yang, C. Zhao, J. Wang, C. Zhao, Y. Hu, G. Wu, Q. Zhang, Q. Xu, B. Liu, P. Gao, R. You, W. Huang, L. Zheng, L. Gu, Y. Wu, Y. Li. J. Am. Chem. Soc. 141(2019) 4505-4509.
[59]	K. Jiang, B. Liu, M. Luo, S. Ning, M. Peng, Y. Zhao, Y.R. Lu, T.S. Chan, F.M. F. de Groot, Y. Tan, Nat.Commun. 10(2019)1743.
[60]	M. Fan, Y. Huang, F. Yuan, Q. Hao, J. Yang, D. Sun, J. Power Sources 366 (2017) 143-150.
[61]	L. Hao, S. Zhang, R. Liu, J. Ning, G. Zhang, L. Zhi, Adv. Mater. 27(2015) 3190-3195.
[62]	Y. Huang, K. Tang, F. Yuan, W. Zhang, B. Li, F. Seidi, H. Xiao, D. Sun, Carbon 168 (2020) 12-21.
[63]	H. Yu, L. Shang, T. Bian, R. Shi, G.I.N. Waterhouse, Y. Zhao, C. Zhou, L.Z. Wu, C.H. Tung, T. Zhang, Adv. Mater. 28(2016) 5080-5086.
[64]	F. Pan, B. Li, W. Deng, Z. Du, Y. Gang, G. Wang, Y. Li, Appl. Catal. B 252 (2019) 240-249.
[65]	F. Pan, B. Li, X. Xiang, G. Wang, Y. Li, ACS Catal 9 (2019) 2124-2133.
[66]	S. Liu, M.G. White, P. Liu, J. Phys. Chem. C 120 (2016) 15288-15298.