Photochemical conversion of CO2 into high-value C2+ products is difficult to achieve due to the energetic and mechanistic challenges in forming multiple C-C bonds. Herein, an efficient photocatalyst for the conversion of CO2 into C3H8 is prepared by implanting Cu single atoms on Ti0.91O2 atomically-thin single layers. Cu single atoms promote the formation of neighbouring oxygen vacancies (VOs) in Ti0.91O2 matrix. These oxygen vacancies modulate the electronic coupling interaction between Cu atoms and adjacent Ti atoms to form a unique Cu-Ti-VO unit in Ti0.91O2 matrix. A high electron-based selectivity of 64.8% for C3H8 (product-based selectivity of 32.4%), and 86.2% for total C2+ hydrocarbons (product-based selectivity of 50.2%) are achieved. Theoretical calculations suggest that Cu-Ti-VO unit may stabilize the key *CHOCO and *CH2OCOCO intermediates and reduce their energy levels, tuning both C1-C1 and C1-C2 couplings into thermodynamically-favourable exothermal processes. Tandem catalysis mechanism and potential reaction pathway are tentatively proposed for C3H8 formation, involving an overall (20e− – 20H+) reduction and coupling of three CO2 molecules at room temperature.

Hexagonal boron nitride (h-BN), an emerging two-dimensional material, has attracted great attention in various fields. However, due to its large band gap (ca. 6 eV), h-BN has not yet been exploited as a photocatalyst. Here, we demonstrate a porous h-BN sheets with rich hydroxyl (-OH) and secondary amino (-NH) groups, which can effectively decrease the band gap of h-BN. Porous h-BN sheets were synthesized via combustion of boron acid and urea at high temperature under nitrogen atmosphere. The as-obtained porous h-BN has a narrower band gap and a higher photocatalytic activity on hydrogen evolution than commercial h-BN. To further understand this photocatalytic performance, we investigated the groups, structure, and related optical and electrochemical properties for both porous and commercial h-BN. This work holds promise for h-BN to be used in the photocatalysis field.

Different conformations, including planar, corrugated, as well as the deficient structure of the two-dimensional materials, play a relevant role in determining their catalytic reaction performances. Here, we systematically investigated the stabilities, electronic properties, and nitrogen activities capacity of various vacancy-modified g-C3N4 considering two different conformations (planar and corrugated) to explore the effects of nitrogen vacancy (NV) and conformations on the photocatalytic performance of g-C3N4 by means of density functional theory computations. Our results found that not only can the nitrogen vacancy (NV) promote separation efficiency of the photoinduced carriers in g-C3N4 but also the distortion conformation can activate more n → π* transitions of NV g-C3N4, resulting in a red shift of optical absorption spectra. More importantly, our results reveal that the corrugation configuration structure, compared to planar conformation, is much more favorable to photocatalytic nitrogen fixation reaction from the aspects of nitrogen absorption capacity and free-energy change, in which corrugation model with N2C vacancy has the smallest onset potential (1.32 V) for the most difficult step through the alternating pathway.

Supported catalysts have exhibited excellent performance in various reactions. However, the rational design of supported catalysts with high activity and certain selectivity remains a great challenge because of the complicated interfacial effects. Using recently emerged two-dimensional materials supported dual-atom catalysts (DACs@2D) as a prototype, we propose a simple and universal descriptor based on inherent atomic properties (electronegativity, electron type, and number), which can well evaluate the complicated interfacial effects on the electrochemical reduction reactions (i.e., CO 2 , O 2 , and N 2 reduction reactions). Based on this descriptor, activity and selectivity trends in CO 2 reduction reaction are successfully elucidated, in good agreement with available experimental data. Moreover, several potential catalysts with superior activity and selectivity for target products are predicted, such as CuCr/g-C 3 N 4 for CH 4 and CuSn/N-BN for HCOOH. More importantly, this descriptor can also be extended to evaluate the activity of DACs@2D for O 2 and N 2 reduction reactions, with very small errors between the prediction and reported experimental/computational results. This work provides feasible principles for the rational design of advanced electrocatalysts and the construction of universal descriptors based on inherent atomic properties.

Electrocatalytic nitrogen fixation using single-atom catalysts (SACs) offers a promising strategy for the sustainable production of NH3. On the basis of density functional theory, we systematically explored the potential for N2 electroreduction of single-atom catalysts (SACs) covering V, Nb, and Ta transition metal (TM) centers supported by graphene and g-C3N4 substrates. The single Nb-atom embedded on g-C3N4 nanosheet possesses outstanding nitrogen reduction reaction (NRR) catalytic activity and exhibits better performance than graphene with a considerably smaller maximum ΔG value (0.05 eV). The single Nb atom on g-C3N4 with more negative valence provides structural advantages for hosting empty d-orbitals for strong N2 and N2H adsorption, as well as more single d-electrons to further promote back-donation to activate the NN triple bond. This work may be helpful in developing more effective TM-based SACs for N2 reduction through varying substrate effect toward the same single-atom catalysts.