Double Z-scheme in SnO_(2)/SnS_(2)/Cu_(2)SnS_(3)heterojunction for photocatalytic reduction of CO_(2)to ethanol

Photocatalytic reduction of CO_(2)to chemical fuels enables a sustainable way of reducing carbon emissions but faces a high reduction potential due to the high stability of CO_(2)molecules.Here,we prepared a SnO_(2)/SnS_(2)/Cu_(2)SnS_(3)double Z-scheme heterojunction photocatalyst,in which SnO_(2),SnS_(2),and Cu_(2)SnS_(3)absorb ultraviolet,visible,and near-infrared light,respectively.Based on the comprehensive analysis of in-situ X-ray photoelectron spectroscopy and photo(chemical)characterizations,we find that the photogenerated electrons would transfer from SnO_(2)to SnS_(2)to Cu_(2)SnS_(3).The optimized SnO_(2)/SnS_(2)/Cu_(2)SnS_(3)–0.3 double Z-scheme heterojunction could achieve 28.44μmol g^(–1)h^(–1)ethanol yield and 92%selectivity,which is roughly 3 folds higher than SnO_(2)/SnS_(2)single Z-scheme heterojunction.By using in-situ diffuse reflectance infrared Fourier-transform spectroscopy,we observe that ethanol is produced through a∗COCOH pathway,in which Cu_(2)SnS_(3)would decrease the activation energy barrier from^(∗)COOH to^(∗)CO.

Synergistic effect of oxygen species and vacancy for enhanced electrochemical CO_(2) conversion to formate on indium oxide

Indium-based oxides are promising electrocatalysts for producing formate via CO_(2) reduction reaction,in which*OCHO is considered the key intermediate.Here,we identified that the*COOH pathway could be preferential to produce formate on In_(2)O_(3)of In/In_(2)O_(3) heterojunction due to the synergistic effect of oxygen species and vacancy.Specifically,*CO_(2) and *COOH were observed on In_(2)O_(3) and related to formate production by in situ Raman spectroscopy.The theoretical calculations further demonstrated that the energy barrier of the*COOH formation on In_(2)O_(3) was decreased in the presence of oxygen vacancy,similar to or lower than that of the*OCHO formation on the In surface.As a result,a formate selectivity of over 90%was obtained on prepared In/In_(2)O_(3) heterojunction with 343±7mAcm^(-2) partial current density.Furthermore,when using a Si-based photovoltaic as an energy supplier,10.11%solar-to-fuel energy efficiency was achieved.

Porous fixed-bed photoreactor for boosting C-C coupling in photocatalytic CO_(2)reduction

Solar-driven CO_(2)conversion to chemical fuels in an aqueous solution is restricted not only by photocatalysts but also by mass transfer.Here,a regulatable three-phase interface on a porous fixed-bed is constructed for efficient C-C coupling in photocatalytic CO_(2)reduction.The photocatalytic results show that∼90%selectivity towards C^(2+)products is obtained by a Cu/Cd_(0.5)Zn_(0.5)S photocatalyst,with a yield of 6.54μmol/h(an irradiation area of 0.785 cm^(2)),while only 0.94μmol/h(an irradiation area of 19.625 cm^(2))is achieved with a commonly used suspension photocatalytic reactor.We find that under the same CO_(2)feed rate,the local CO_(2)concentration in this porous fixed-bed photoreactor is obviously higher than in the suspension photoreactor.The larger local CO_(2)coverage derived from a higher CO_(2)supply and aggregation enhances the C-C coupling,thereby generating more C^(2+).Even an observable three-phase interface on the porous fixed-bed can be regulated by adjusting the CO_(2)supply,for which the optimal gas inlet rate is 5-10 sccm.

Photochemical Systems for Solar‑to‑Fuel Production

The photochemical system,which utilizes only solar energy and H_(2)O/CO_(2) to produce hydrogen/carbon-based fuels,is considered a promising approach to reduce CO_(2) emissions and achieve the goal of carbon neutrality.To date,numerous photochemical systems have been developed to obtain a viable solar-to-fuel production system with sufficient energy efficiency.However,more effort is still needed to meet the requirements of industrial implementation.In this review,we systematically discuss a typical photochemical system for solar-to-fuel production,from classical theories and fundamental mechanisms to raw material selection,reaction condition optimization,and unit device/system advancement,from the viewpoint of ordered energy conversion.State-of-the-art photochemical systems,including photocatalytic,photovoltaic-electrochemical,photoelectrochemical,solar thermochemical,and other emerging systems,are summarized.We highlight the existing bottlenecks and discuss the developing trend of this technology.Finally,optimization strategies and new opportunities are proposed to enhance photochemical systems with higher energy efficiency.