Insights into photocatalytic CO2 reduction on C3N4: Strategy of simultaneous B, K co-doping and enhancement by N vacancies

C3N4 is a promising non-metal photocatalyst for CO2 conversion to value-added products, while it shows unsatisfactory performance due to the low CO2 adsorption ability and poor utilization of the photo-excited charge carriers. The deficiency of electron donation sites and unoptimized electronic structure are the primary reasons behind. To address the challenges, herein, we propose a new synthesis strategy of rational co-doping of B, K elements in line with controllable introduction of Nv into C3N4 within one step during synthesis. The synergistic effects of the modification factors resulted in an enhanced C3N4 catalyst with an electron-rich surface and tailored electronic structure, which significantly facilitated the CO2 adsorption and activation in sequence. Moreover, the drawback of single element doping is largely avoided due to the synergistic effects provided by this rational multiple modification strategy. A 5-h photocatalytic production of 5.93 μmol g−1 CH4 and 3.16 μmol g−1 CO respectively were achieved using CO2 and H2O as feedstocks without the presence of any organic hole scavenger, which are 161% and 527% of CH4 and CO produced by pristine C3N4.