Fig. 4. Photocatalytic CO₂ hydrogenation using Ni₃N nanosheets.

a Production rate of CO in light at various intensities and dark at different temperatures, b control experiments at 2.5 W cm⁻². No external heating was used; c Production rate and catalyst bed surface temperature during successive light ON and OFF conditions at 2.5 W cm⁻², d Mass spectra of ¹³CO, obtained using labeled ¹³CO₂ as feed; e Long-term stability study under the flow condition using light (at 2.5 W cm⁻²) without external heating. Reaction conditions: H₂ (4 mL min⁻¹), CO₂ (73 mL min⁻¹), xenon lamp (400–1100 nm). Error bars: calculated from data of at least three repeated experiments. NP-nanoparticles, NS-nanosheets. Detailed calculations are given in Supplementary Data 1.