Comment on “Unbiased solar H2 production with current density up to 23 mA cm−2 by Swiss-cheese black Si coupled with wastewater bioanode” by L. Lu, W. Vakki, J. A. Aguiar, C. Xiao, K. Hurst, M. Fairchild, X. Chen, F. Yang, J. Gu and Z. J. Ren, Energy Envi