Cobalt species as active sites for photocatalytic reduction of CO₂ to valuable products such as methanol have received increasing attention, however, it remains a huge challenge to achieve the high activity. Herein, a pyrolysis-induced-vaporization strategy was successfully employed to fabricate Co/g-C₃N₄ single-atom catalysts (Co/g-C₃N₄ SACs) with surface Co atom loading up to 24.6 wt%. Systematic investigation of Co/g-C₃N₄ SACs formation process disclosed that concentrated-H₂SO₄ exfoliation of g-C₃N₄ nanosheets (g-C₃N₄ NSs) as the substrate followed by a two-step calcination process is essential to achieve ultrahigh metal loading. It was found that the ultrahigh-density of Co single-atom sites were anchored on the g-C₃N₄ substrate surface and coordinated with two nitrogen and one carbon atoms (Co-N₂C). These single dispersed Co-N₂C sites on the g-C₃N₄ surface were found to act not only as electron gathering centers but also as the sites of CO₂ adsorption and activation, subsequently, boosting the photocatalytic methanol generation during light irradiation. As a result, the methanol formation rate at 4 h (941.9 μmol g⁻¹) over Co/g-C₃N₄-0.2 SAC with 24.6 wt% surface Co loading was 13.4 and 2.2 times higher than those of g-C₃N₄ (17.7 μmol g⁻¹) and aggregated CoO_x/g-C₃N₄-0.2 (423.9 μmol g⁻¹), respectively. Simultaneously, H₂ (18.9 μmol g⁻¹ h⁻¹), CO (2.9 μmol g⁻¹ h⁻¹), CH₄ (3.4 μmol g⁻¹ h⁻¹), C₂H₄ (1.1 μmol g⁻¹ h⁻¹), C₃H₆ (1.4 μmol g⁻¹ h⁻¹), and CH₃OCH₃ (3.3 μmol g⁻¹ h⁻¹) products were detected over Co/g-C₃N₄-0.2 SAC. Besides, the photocatalytic activity of the Co/g-C₃N₄-0.2 SAC for the reduction of CO₂ to methanol was stable within 12-cycle experiments (~48 h). This work paves a strategy to boost the photoreduction CO₂ activity via loading ultrahigh surface density single atomically dispersed cobalt active sites.

钴物种作为光催化将 CO ₂还原为有价值的产物（如甲醇）的活性位点受到越来越多的关注，然而，实现高活性仍然是一个巨大的挑战。在此，成功地采用热解诱导蒸发策略来制造表面 Co​​ 原子负载高达 24.6 wt% 的Co/gC ₃ N ₄单原子催化剂（Co/gC ₃ N ₄ SAC）。的Co / GC的系统的调查_3点Ñ ₄的SAC形成工艺公开了浓缩的-H ₂ SO ₄ GC的剥离_3个Ñ ₄纳米片（GC ₃ Ñ₄ NSs）作为基材，然后进行两步煅烧工艺对于实现超高金属负载至关重要。发现超高密度的Co单原子位点锚定在gC ₃ N ₄衬底表面并与两个氮和一个碳原子（Co-N ₂ C）配位。发现gC ₃ N ₄表面上的这些单个分散的 Co-N ₂ C 位点不仅充当电子聚集中心，还充当 CO ₂吸附和活化位点，随后在光照射期间促进光催化甲醇的生成。因此，Co/gC上 4 小时的甲醇形成速率 (941.9 μmol g ^-1 )具有 24.6 wt% 表面 Co​​ 负载的₃ N ₄ -0.2 SAC 是 gC ₃ N ₄ (17.7 μmol g ^-1 ) 和聚集 CoO _x /gC ₃ N ₄ -0.2 (423.9 μmol g ^-1 ) 的13.4 和 2.2 倍）， 分别。同时，H ₂ (18.9 μmol g ^-1 h ^-1 )、CO (2.9 μmol g ^-1 h ^-1 )、CH ₄ (3.4 μmol g ^-1 h ^-1 )、C ₂ H ₄ (1.1 μmol g ^-1 h ^-1 ), C ₃H ₆ (1.4 μmol g ^-1 h ^-1 )和CH ₃ OCH ₃ (3.3 μmol g ^-1 h ^-1 )产物通过Co/gC ₃ N ₄ -0.2 SAC检测。此外，Co/gC ₃ N ₄ -0.2 SAC 将 CO ₂还原为甲醇的光催化活性在 12 个循环实验（~48 小时）内是稳定的。这项工作为通过加载超高表面密度单原子分散钴活性位点来提高光还原 CO ₂活性铺平了道路。