Hydrogen is one of the cleanest and most promising energy carriers as an alternative energy source.^{1, 2} The production of hydrogen from water via a hydrogen evolution reaction (HER) has been widely studied. Platinum is believed to have the highest electrocatalytic activity for HER in both acidic and alkaline solutions. But it is very expensive and rare. Thus, more advanced precious metal free electrocatalysts for HER are required to lower the cost of electrolyzers. ^{3, 4}

In this study, carbon-based non-precious metal catalysts (Me-N-C) were synthesized by impregnating aniline and different metal salts into a carbon matrix and pyrolyzing at 900℃ in N₂ atmosphere.^{5, 6} The structure of obtained composites were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy and X-ray diffraction. Their hydrogen evolution reaction (HER) activities were investigated in both 0.5 M H₂SO₄and 1 M KOH. For the first time, these non-precious metal electrocatalysts showed excellent activity for HER and good stability in both acidic and alkaline media. The Ni-C-N catalyst had the lowest onset potential while Co, Fe-C-N catalysts had smaller Tafel slopes than the former (Figure 1a).

Various active sites could contribute to the HER activity in Me-N-C catalysts (Figure 1b). Density functional theory (DFT) calculations were employed to understand the activity enhancement mechanisms and identify the active center. This work paved a new route in the design of cheap, robust and high efficient catalysts to replace Pt.

References

1. Zhou, W.; Zhou, J.; Zhou, Y.; Lu, J.; Zhou, K.; Yang, L.; Tang, Z.; Li, L.; Chen, S. Chemistry of Materials 2015, 27, (6), 2026-2032.
2. Fei, H.; Dong, J.; Arellano-Jiménez, M. J.; Ye, G.; Kim, N. D.; Samuel, E. L.; Peng, Z.; Zhu, Z.; Qin, F.; Bao, J. Nature communications 2015, 6.
3. Deng, J.; Ren, P.; Deng, D.; Yu, L.; Yang, F.; Bao, X. Energy & Environmental Science 2014, 7, (6), 1919-1923.
4. Zou, X.; Huang, X.; Goswami, A.; Silva, R.; Sathe, B. R.; Mikmeková, E.; Asefa, T. Angewandte Chemie 2014, 126, (17), 4461-4465.
5. Merzougui, B.; Hachimi, A.; Akinpelu, A.; Bukola, S.; Shao, M. Electrochimica Acta 2013, 107, 126-132.
6. Wu, G.; More, K. L.; Johnston, C. M.; Zelenay, P. Science 2011, 332, (6028), 443-447.