氮化硅是一种良好的载体,具有较高的水热稳定性和机械稳定性,其表面的氨基基团能够较好地锚定金属,显著提高金属分散度。但是,商品氮化硅比表面积较低,对金属分散作用仍然有限。因此,以自制的高比表面积氮化硅(Si_(3)N_(4))为载体,通过...氮化硅是一种良好的载体,具有较高的水热稳定性和机械稳定性,其表面的氨基基团能够较好地锚定金属,显著提高金属分散度。但是,商品氮化硅比表面积较低,对金属分散作用仍然有限。因此,以自制的高比表面积氮化硅(Si_(3)N_(4))为载体,通过浸渍法制备了不同Ru负载量(质量分数分别为0.5%、1.0%和2.0%)的催化剂(分别为0.5%Ru/Si_(3)N_(4)、1.0%Ru/Si_(3)N_(4)和2.0%Ru/Si_(3)N_(4)),并以商品氮化硅(Si_(3)N_(4)-C)为载体制备了2.0%Ru/Si_(3)N_(4)-C催化剂作为对照组。表征了催化剂的理化性质,测试了其在300℃、0.1 MPa下的CO_(2)加氢反应活性。结果显示,与Si_(3)N_(4)-C相比,Si_(3)N_(4)的比表面积较高(502 m^(2)/g),Si_(3)N_(4)作为载体显著提高了金属分散度,降低了金属粒径,催化剂暴露出更多的活性位点。0.5%Ru/Si_(3)N_(4)的金属粒径较小,展现出强的H_(2)吸附能力,H难以解吸,抑制了中间物种CO加氢生成CH_(4)。随着Ru负载量增加,金属粒径增大,催化剂的CH_(4)选择性更好。Ru/Si_(3)N_(4)系列催化剂中,2.0%Ru/Si_(3)N_(4)的CH_(4)选择性较高(98.8%)。空速为10000 m L/(g·h)时,0.5%Ru/Si_(3)N_(4)的CO选择性为88.2%。与2.0%Ru/Si_(3)N_(4)相比,2.0%Ru/Si_(3)N_(4)-C的金属粒径更大,活性位点较少,活性更低。2.0%Ru/Si_(3)N_(4)和2.0%Ru/Si_(3)N_(4)-C的CO_(2)转化率分别为53.1%和9.2%。Si_(3)N_(4)有效提高了金属分散度,提高了催化剂的CO_(2)加氢反应活性;通过调控Ru负载量控制催化剂金属粒径,可实现对产物CO或CH_(4)选择性的调控。展开更多
Herein,the catalysts of ultrathin g-C_(3)N_(4)surface-modified hollow spherical Bi2MoO6(g-C_(3)N_(4)/Bi2MoO6,abbreviated as CN/BMO)were fabricated by the co-solvothermal method.The variable valence Mo^(5+)/Mo^(6+)ioni...Herein,the catalysts of ultrathin g-C_(3)N_(4)surface-modified hollow spherical Bi2MoO6(g-C_(3)N_(4)/Bi2MoO6,abbreviated as CN/BMO)were fabricated by the co-solvothermal method.The variable valence Mo^(5+)/Mo^(6+)ionic bridge in CN/BMO catalysts can boost the rapid transfer of photogenerated electrons from Bi2MoO6to g-C_(3)N_(4).And the synergy effect of g-C_(3)N_(4)and Bi2MoO6components remarkably enhance CO_(2)adsorption capability.CN/BMO-2 catalyst has the best performances for visible light-driven CO_(2)reduction compared with single Bi2MoO6and g-C_(3)N_(4),i.e.,its amount and selectivity of CO product are 139.50μmol g-1and 96.88%for 9 h,respectively.Based on the results of characterizations and density functional theory calculation,the photocatalytic mechanism for CO_(2)reduction is proposed.The high-efficient separation efficiency of photogenerated electron-hole pairs,induced by variable valence Mo^(5+)/Mo^(6+)ionic bridge,can boost the rate-limiting steps(COOH*-to-CO*and CO*desorption)of selective visible light-driven CO_(2)conversion into CO.It inspires the establishment of efficient photocatalysts for CO_(2)conversion.展开更多
文摘氮化硅是一种良好的载体,具有较高的水热稳定性和机械稳定性,其表面的氨基基团能够较好地锚定金属,显著提高金属分散度。但是,商品氮化硅比表面积较低,对金属分散作用仍然有限。因此,以自制的高比表面积氮化硅(Si_(3)N_(4))为载体,通过浸渍法制备了不同Ru负载量(质量分数分别为0.5%、1.0%和2.0%)的催化剂(分别为0.5%Ru/Si_(3)N_(4)、1.0%Ru/Si_(3)N_(4)和2.0%Ru/Si_(3)N_(4)),并以商品氮化硅(Si_(3)N_(4)-C)为载体制备了2.0%Ru/Si_(3)N_(4)-C催化剂作为对照组。表征了催化剂的理化性质,测试了其在300℃、0.1 MPa下的CO_(2)加氢反应活性。结果显示,与Si_(3)N_(4)-C相比,Si_(3)N_(4)的比表面积较高(502 m^(2)/g),Si_(3)N_(4)作为载体显著提高了金属分散度,降低了金属粒径,催化剂暴露出更多的活性位点。0.5%Ru/Si_(3)N_(4)的金属粒径较小,展现出强的H_(2)吸附能力,H难以解吸,抑制了中间物种CO加氢生成CH_(4)。随着Ru负载量增加,金属粒径增大,催化剂的CH_(4)选择性更好。Ru/Si_(3)N_(4)系列催化剂中,2.0%Ru/Si_(3)N_(4)的CH_(4)选择性较高(98.8%)。空速为10000 m L/(g·h)时,0.5%Ru/Si_(3)N_(4)的CO选择性为88.2%。与2.0%Ru/Si_(3)N_(4)相比,2.0%Ru/Si_(3)N_(4)-C的金属粒径更大,活性位点较少,活性更低。2.0%Ru/Si_(3)N_(4)和2.0%Ru/Si_(3)N_(4)-C的CO_(2)转化率分别为53.1%和9.2%。Si_(3)N_(4)有效提高了金属分散度,提高了催化剂的CO_(2)加氢反应活性;通过调控Ru负载量控制催化剂金属粒径,可实现对产物CO或CH_(4)选择性的调控。
基金supported by the National Natural Science Foundation of China(21972166)the Beijing Natural Science Foundation(2202045)the National Key Research and Development Program of China(2019YFC1907600)。
文摘Herein,the catalysts of ultrathin g-C_(3)N_(4)surface-modified hollow spherical Bi2MoO6(g-C_(3)N_(4)/Bi2MoO6,abbreviated as CN/BMO)were fabricated by the co-solvothermal method.The variable valence Mo^(5+)/Mo^(6+)ionic bridge in CN/BMO catalysts can boost the rapid transfer of photogenerated electrons from Bi2MoO6to g-C_(3)N_(4).And the synergy effect of g-C_(3)N_(4)and Bi2MoO6components remarkably enhance CO_(2)adsorption capability.CN/BMO-2 catalyst has the best performances for visible light-driven CO_(2)reduction compared with single Bi2MoO6and g-C_(3)N_(4),i.e.,its amount and selectivity of CO product are 139.50μmol g-1and 96.88%for 9 h,respectively.Based on the results of characterizations and density functional theory calculation,the photocatalytic mechanism for CO_(2)reduction is proposed.The high-efficient separation efficiency of photogenerated electron-hole pairs,induced by variable valence Mo^(5+)/Mo^(6+)ionic bridge,can boost the rate-limiting steps(COOH*-to-CO*and CO*desorption)of selective visible light-driven CO_(2)conversion into CO.It inspires the establishment of efficient photocatalysts for CO_(2)conversion.