Photocatalysis has been invariably considered as an unselective process (especially in water) for a fairly long period of time, and the investigation on selective photocatalysis has been largely neglected. In recent years, the field of selective photocatalysis is developing rapidly and now extended to several newer applications. This review focuses on the overall strategies which can improve the selectivity of photocatalysis encompassing a wide variety of photocatalysts, and modifications thereof, as well as the related vital processes of industrial significance such as reduction and oxidation of organics, inorganics, and CO transformation. Comprehensive and successful strategies for enhancing the selectivity in photocatalysis are abridged to reinvigorate and stimulate future investigations. In addition, nonsemiconductor type photocatalysts, such as Ti-Si molecular sieves and carbon quantum dots (CQDs), are also briefly appraised in view of their special role in special selective photocatalysis, namely epoxidation reactions, among others. In the end, a summary and outlook on the challenges and future directions in the research field are included in the comprehensive review.

Active and durable electrocatalysts for methanol oxidation reaction are of critical importance to the commercial viability of direct methanol fuel cell technology. Unfortunately, current methanol oxidation electrocatalysts fall far short of expectations and suffer from rapid activity degradation. Here we report platinum–nickel hydroxide–graphene ternary hybrids as a possible solution to this long-standing issue. The incorporation of highly defective nickel hydroxide nanostructures is believed to play the decisive role in promoting the dissociative adsorption of water molecules and subsequent oxidative removal of carbonaceous poison on neighbouring platinum sites. As a result, the ternary hybrids exhibit exceptional activity and durability towards efficient methanol oxidation reaction. Under periodic reactivations, the hybrids can endure at least 500,000 s with negligible activity loss, which is, to the best of our knowledge, two to three orders of magnitude longer than all available electrocatalysts.

With the rapid development of industry, heavy metal pollution has become a potential hazard to public health and the ecological system. Herein, molybdenum disulfide coated Mg/Al layered double hydroxide composites (LDHs@MoS2) were prepared via a simple hydrothermal method and applied for the adsorption of Cr­(VI) from a water solution. The removal capacity of Cr­(VI) on LDHs@MoS2 reached 76.3 mg/g at pH = 5.0, and the removal process relied on ionic strength and pH. The results confirmed that the uptake of Cr­(VI) on LDHs@MoS2 followed a spontaneous endothermic process. In contrast to the LDHs, LDHs@MoS2 showed excellent chemical stability, which was beneficial for practical applications. Specifically, the coexisting ions had little influence on the uptake of Cr­(VI). The interaction of Cr­(VI) with the LDHs@MoS2 composites was mainly controlled by electrostatic attraction and outer-sphere surface complexation. The findings can provide new insights into the uptake of heavy metal ions in a natural aquatic environment pollution cleanup.

The widespread heterojunction or p–n junction strategies fabricated between different semiconductors are generally used to promote the spatial charge separation in photocatalysis and solar cells, which originated from the principle that the junction composites possess totally different crystalline and energy structures. A vagarious and supreme challenge remained as to whether a junction could be formed between the identical composites with the same semiconductors and the crystalline phases. Herein, taking model semiconductor TiO2 as a prototype and proof-of-concept, a homophase junction was fabricated between the same crystalline phases of TiO2 with large and small nanoparticles. Photocatalytic H2 evolution and water splitting performances on three common TiO2 phases, brookite, anatase, and rutile, can be remarkably enhanced using such homophase junction strategy. The high photocatalytic activities are proposed to be attributed to the different surface band bending inducing the formation of a built-in electric field at the interface of large and small particles, which facilitates the spatial charge separation and inhibits the charge recombination. Our work provides a strategy for spatial charge separation in constructing highly efficient solar energy conversion systems, which is differentiated from the traditional junction strategies.

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The nature behind the promotional effect of phosphorus on the catalytic performance and hydrothermal stability of zeolite H-ZSM-5 has been studied using a combination of (27) Al and (31) P MAS NMR spectroscopy, soft X-ray absorption tomography and n-hexane catalytic cracking, complemented with NH3 temperature-programmed desorption and N2 physisorption. Phosphated H-ZSM-5 retains more acid sites and catalytic cracking activity after steam treatment than its non-phosphated counterpart, while the selectivity towards propylene is improved. It was established that the stabilization effect is twofold. First, the local framework silico-aluminophosphate (SAPO) interfaces, which form after phosphatation, are not affected by steam and hold aluminum atoms fixed in the zeolite lattice, preserving the pore structure of zeolite H-ZSM-5. Second, the four-coordinate framework aluminum can be forced into a reversible sixfold coordination by phosphate. These species remain stationary in the framework under hydrothermal conditions as well. Removal of physically coordinated phosphate after steam-treatment leads to an increase in the number of strong acid sites and increased catalytic activity. We propose that the improved selectivity towards propylene during catalytic cracking can be attributed to local SAPO interfaces located at channel intersections, where they act as impediments in the formation of bulky carbenium ions and therefore suppress the bimolecular cracking mechanism.

Understanding the structure–performance relationship for Fe-based Fischer–Tropsch synthesis (FTS) catalysts is crucial for the design of improved FTS catalysts. Herein, catalysts derived from four pure phases of iron (i.e., nanosized Fe2O3, χ-Fe5C2, θ-Fe3C, and Fe0) were obtained under controlled conditions. Combining various surface and bulk characterization techniques, we revealed that core–shell structures were formed for all catalysts irrespective of the catalyst precursors, while the compositions within the core and shell strongly depend on the intrinsic properties of the precursors employed. Most importantly, we report that the iron coordination environment mainly governs the performance during FTS. The iron time yield is found to correlate linearly with the average bulk iron oxidation state rather than the surface properties, and the CH4 yield is related to the coordination number of the Fe–C bond. This study thus provides general descriptors to interpret the structure–performance relationships of Fe-based FTS catalysts.

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