Highly efficient photocatalytic reduction of CO2 to CO using cobalt oxide-coated spherical mesoporous silica particles as catalysts.

New spherical hybrid materials as-synthesized by Cobalt oxide nanoparticles immobilized in situ on the outside surfaces of mesoporous silica particles exhibited highly efficient visible-light-driven catalytic performance towards CO2-to-CO conversion. An average generation rate of CO of up to 25 626 µmol h-1 g-1 with a selectivity of 83.0% was achieved.

An Unexpected Iron (II)-Based Homogeneous Catalytic System for Highly Efficient CO2-to-CO Conversion under Visible-Light Irradiation.

We present two as-synthesized Fe(II)-based molecular catalysts with 1,10-phenanthroline (phen) ligands; Fe(phen)3Cl2 (1) and [Fe(phen)2(CH3CH2OH)Cl]Cl (2), and their robust catalytic properties for the conversion of CO2 to CO in DMF/TEOA (DMF = N,N'-dimethylformamide; TEOA = triethanolamine) solution containing Ru(bpy)32+ and BIH (1,3-dimethyl-2-phenyl-2,3- dihydro-1H-benzo-[d]-imidazole). High turnover numbers (TONs) of 19,376 were achieved with turnover frequencies (TOFs) of 3.07 s-1 for complex 1 (1.5 × 10-7 M). A quantum efficiency of 0.38% was observed after 5 h irradiated by 450 nm monochromatic light. The generation rate of CO2 and H2 were tuned by optimizing the experimental conditions, resulting in a high CO selectivity of 90%. The remarkable contribution of the photosensitizer to the total TONCO was found being 19.2% (as shown by tests under similar conditions without catalysts) when BIH was employed as a sacrificial electron donor. The product selectivity in complex 2 reached 95%, and the corresponding TONCO and TOFCO were 33,167 and 4.61 s-1 in the same concentration with complex 1 used as catalyst; respectively. This work provides guidance for future designs of simple, highly efficient and selective molecular catalytic systems that facilitate carbon-neutral solar-to-fuel conversion processes.

An Exceptionally Efficient Co-Co2 P@N, P-Codoped Carbon Hybrid Catalyst for Visible Light-Driven CO2 -to-CO Conversion.

Artificial photosynthesis has attracted wide attention, particularly the development of efficient solar light-driven methods to reduce CO2 to form energy-rich carbon-based products. Because CO2 reduction is an uphill process with a large energy barrier, suitable catalysts are necessary to achieve this transformation. In addition, CO2 adsorption on a catalyst and proton transfer to CO2 are two important factors for the conversion reaction, and catalysts with high surface area and more active sites are required to improve the efficiency of CO2 reduction. Here, a visible light-driven system for CO2 -to-CO conversion is reported, which consists of a heterogeneous hybrid catalyst of Co and Co2 P nanoparticles embedded in carbon nanolayers codoped with N and P (Co-Co2 P@NPC) and a homogeneous RuII -based complex photosensitizer. The average generation rate of CO of the system was up to 35 000 µmol h-1 g-1 with selectivity of 79.1 % in 3 h. Linear CO production at an exceptionally high rate of 63 000 µmol h-1 g-1 was observed in the first hour of reaction. Inspired by this highly active catalyst, Co@NC and Co2 P@NPC materials were also synthesized and their structure, morphology, and catalytic properties for CO2 photoreduction were explored. The results showed that the nanoparticle size, partially adsorbed H2 O molecules on the catalyst surface, and the hybrid nature of the systems influenced their photocatalytic CO2 reduction performance.

Highly Efficient Photocatalytic System Constructed from CoP/Carbon Nanotubes or Graphene for Visible-Light-Driven CO2 Reduction.

Visible-light-driven conversion of CO2 to CO and high-value-added carbon products is a promising strategy for mitigating CO2 emissions and reserving solar energy in chemical form. We report an efficient system for CO2 transformation to CO catalyzed by bare CoP, hybrid CoP/carbon nanotubes (CNTs), and CoP/reduced graphene oxide (rGO) in mixed aqueous solutions containing a Ru-based photosensitizer, under visible-light irradiation. The in situ prepared hybrid catalysts CoP/CNT and CoP/rGO show excellent catalytic activities in CO2 reduction to CO, with a catalytic rates of up to 39 510 and 47 330 µmol h-1 g-1 in the first 2 h of reaction, respectively; a high CO selectivity of 73.1 % for the former was achieved in parallel competing reactions in the photoreduction of CO2 and H2 O. A combination of experimental and computational studies clearly shows that strong interactions between CoP and carbon-supported materials and partially adsorbed H2 O molecules on the catalyst surface significantly improve CO-generating rates.

Highly efficient hydrolysis of ammonia borane by anion (-OH, F-, Cl-)-tuned interactions between reactant molecules and CoP nanoparticles.

The CoP nanoparticle catalyst had excellent catalytic activity and a short catalytic induction period in the presence of anions, and high sustainability in ammonia borane hydrolysis, with an initial turnover frequency of 72.2 mol(H2) mol(CoP)-1 min-1 at ambient temperature. This value is unprecedented for noble-metal-free catalytic systems.