Fig. 8. (a) Schematic of the tentative photocatalytic mechanisms and reaction pathway of Cu–CCN for pCO₂RR. (b) Schematic illustration of Cu/CN hybrid for pCO₂RR. (c) Photocatalytic selective CO₂RR on Ni-TpBpy. (d) Proposed reaction mechanism for the photoconversion of CO₂ into CO on Ni-TpBpy (reproduced from ref. 192 with permission from American Chemical Society, copyright 2020; reproduced from ref. 165 with permission from American Chemical Society, copyright 2020; reproduced from ref. 194 with permission from American Chemical Society, copyright 2019).