Understanding of the structural evolution of catalysts and identification of active species during CO_(2) conversion

Converting CO_(2) into value-added chemicals and fuels through various catalytic methods to lower the atmospheric CO_(2) concentration has been developed to be a crucial means to alleviate the energy shortage and ameliorate the ever-fragile environment status. However, the complexity of the CO_(2) conversion reaction and the strong reduction conditions lead to the inevitable structural evolution, making it difficult for the prior design of suitable catalytic materials. Herein, to guide the rational design of efficient catalysts,we will be centered on the thermal, electro, and photo-induced structural evolution and active species identification during the CO_(2) conversion, including the in situ/operando characterization techniques monitoring the activation, steady, and deactivation stage of the catalysts as well as the inherent restructuring mechanism towards active species. Besides, the future challenges and opportunities on the merits of combining the structural evolution with the adsorbed intermediates recognized by ultra-fast spectroscopic techniques, simultaneously, the combination of theoretical simulation and the results of in situ experiments will also be addressed. This review can not only guide the identification of real active species, but also provide an approach to design the specific active species towards CO_(2) conversion, rather than only focusing on activity, for the purpose of practical industrial application.

Integrating photocatalytic reduction of CO2 with selective oxidation of tetrahydroisoquinoline over InP–In2O3 Z-scheme p-n junction

The development of a facile strategy to construct stable hierarchal porous heterogeneous photocatalysts remains a great challenge for efficient CO2 reduction.Additionally,hole-trapping sacrificial agents(e.g.,triethanolamine,triethylamine,and methanol)are mostly necessary,which produce useless chemicals,and thus cause costs/environmental concerns.Therefore,utilizing oxidation ability of holes to develop an alternative photooxidation reaction to produce value-added chemicals,especially coupled with CO2 photoreduction,is highly desirable.Here,an in situ partial phosphating method of In2O3 is reported for synthesizing In P–In2O3 p-n junction.A highly selective photooxidation of tetrahydroisoquinoline(THIQ)into value-added dihydroisoquinoline(DHIQ)is to replace the hole driven oxidation of typical sacrificial agents.Meanwhile,the photoelectrons of In P–In2O3 p-n junction can induce the efficient photoreduction of CO2 to CO with high selectivity and stability.The evolution rates of DHIQ and CO are 2 and 3.8 times higher than those of the corresponding In2O3 n-type precursor,respectively.In situ irradiated X-ray photoelectron spectroscopy and electron spin resonance are utilized to confirm that the direct Z-scheme mechanism of In P–In2O3 p-n junction accelerate the efficient separation of photocarriers.

Mechanistic insight into the controlled synthesis of metal phosphide catalysts from annealing of metal oxides with sodium hypophosphite

Understanding and manipulating synthetic progress for precisely controlling the components and defects of nanomaterials is an important and challenging task in materials synthesis and nanocatalysis.Metal phosphides(MPs)have been explored as cheap advanced materials in various catalytic fields.MP materials are usually synthesized through gas-solid phosphorization reaction in a trial-to-error manner,but their formation mechanism and the origin of controlled synthesis remain unclear.Here,we combine in situ thermogravimetrc analysis-mass spectrometry(TG-MS)and quasi-in situ X-ray powder diffraction(XRD)analysis to probe the transformation mechanism from metal oxides(MOs)to MPs during the phosphorization process mediated by hypophosphite.Temperature,time,and the amount of hypophosphite are revealed as the driven forces while oxophilicity and crystallinity as the impeded forces,simultaneously control the component and defect level of a series of MP(M=Ni,Co,W,Mo,and Nb).The as-obtained WO2.9/WP is proved to be an efficient Z-scheme photocatalyst for oxidative coupling of methane with the total C2+production and C2H4 selectivity in C2+products reaching 10.75 pmolg-1 and 98.25%.Our work provides a fundamental understanding of the phosphorization treatment and thereby guides a viable synthetic route to the controlled synthesis of MOx-δ,MP,MOx-δ/MP,and MP/M heterostructured materials.