Wenguang Tu

Nickel Nanoparticles Encapsulated in Few-Layer Nitrogen-Doped Graphene Derived from Metal–Organic Frameworks as Efficient Bifunctional Electrocatalysts for Overall Water Splitting

Nickel nanoparticles encapsulated in few-layer nitrogen-doped graphene (Ni@NC) are synthesized by using a Ni-based metal-organic framework as the precursor for high-temperature annealing treatment. The resulting Ni@NC materials exhibit highly efficient and ultrastable electrocatalytic activity toward the hydrogen evolution reaction and the oxygen evolution reaction as well as overall water splitting in alkaline environment.

Metal-free photocatalysts for various applications in energy conversion and environmental purification

During the past few decades, photocatalysis as a green and sustainable technology has received increasing attention owing to its potential to solve energy and environmental problems. For the purpose of obtaining highly efficient and low-cost photocatalysts, various metal-free photocatalytic materials have been designed and developed in recent years for energy conversion and environmental purification because of their unique properties and characteristics. This critical review presents the recent crucial applications and progress in metal-free photocatalysis, including photocatalytic water reduction for H2 evolution, photocatalytic CO2 reduction, photoremoval of NOx, photodegradation of pollutants and so on. The review also ends with some study highlights and suggestions for future research topics. We hope this review can facilitate deep-level investigation on the subject and provide new opportunities to develop metal-free photocatalytic materials with other important applications in the future.

A Highly Efficient Oxygen Evolution Catalyst Consisting of Interconnected Nickel–Iron‐Layered Double Hydroxide and Carbon Nanodomains

In this work, a one-pot solution method for direct synthesis of interconnected ultrafine amorphous NiFe-layered double hydroxide (NiFe-LDH) (<5 nm) and nanocarbon using the molecular precursor of metal and carbon sources is presented for the first time. During the solvothermal synthesis of NiFe-LDH, the organic ligand decomposes and transforms to amorphous carbon with graphitic nanodomains by catalytic effect of Fe. The confined growth of both NiFe-LDH and carbon in one single sheet results in fully integrated amorphous NiFe-LDH/C nanohybrid, allowing the harness of the high intrinsic activity of NiFe-LDH due to (i) amorphous and distorted LDH structure, (ii) enhanced active surface area, and (iii) strong coupling between the active phase and carbon. As such, the resultant NiFe-LDH/C exhibits superior activity and stability. Different from postdeposition or electrostatic self-assembly process for the formation of LDH/C composite, this method offers one new opportunity to fabricate high-performance oxygen evolution reaction and possibly other catalysts.

Rational Design of Catalytic Centers in Crystalline Frameworks

Crystalline frameworks including primarily metal organic frameworks (MOF) and covalent organic frameworks (COF) have received much attention in the field of heterogeneous catalysts recently. Beyond providing large surface area and spatial confinement, these crystalline frameworks can be designed to either directly act as or influence the catalytic sites at molecular level. This approach offers a unique advantage to gain deeper insights of structure-activity correlations in solid materials, leading to new guiding principles for rational design of advanced solid catalysts for potential important applications related to energy and fine chemical synthesis. In this review, recent key progress achieved in designing MOF- and COF-based molecular solid catalysts and the mechanistic understanding of the catalytic centers and associated reaction pathways are summarized. The state-of-the-art rational design of MOF- and COF-based solid catalysts in this review is grouped into seven different areas: (i) metalated linkers, (ii) metalated moieties anchored on linkers, (iii) organic moieties anchored on linkers, (iv) encapsulated single sites in pores, and (v) metal-mode-based active sites in MOFs. Along with this, some attention is paid to theoretical studies about the reaction mechanisms. Finally, technical challenges and possible solutions in applying these catalysts for practical applications are also presented.

Anchoring Active Pt2+/Pt0 Hybrid Nanodots on g-C3N4 Nitrogen Vacancies for Photocatalytic H2 Evolution

A Pt2+ /Pt0 hybrid nanodot-modified graphitic carbon nitride (CN) photocatalyst (CNV-P) was fabricated for the first time using a chemical reduction method, during which nitrogen vacancies in g-C3 N4 assist to stabilize Pt2+ species. It is elucidated that the coexistence of metallic Pt0 and Pt2+ species in the Pt nanodots loaded on g-C3 N4 results in superior photocatalytic H2 evolution performance with very low Pt loadings. The turnover frequencies (TOFs) are 265.91 and 116.38 h-1 for CNV-P-0.1 (0.1 wt % Pt) and CNV-P-0.5 (0.5 wt % Pt), respectively, which are much higher than for other g-C3 N4 -based photocatalysts with Pt co-catalyst reported previously. The excellent photocatalytic H2 evolution performance is a result of i) metallic Pt0 facilitating the electron transport and separation and Pt2+ species preventing the undesirable H2 backward reaction, ii) the strong interfacial contact between Pt2+ /Pt0 hybrid nanodots and nitrogen vacancies of CNV facilitating the interfacial electron transfer, and iii) the highly dispersed Pt2+ /Pt0 hybrid nanodots exposing more active sites for photocatalytic H2 evolution. Our findings are useful for the design of highly active semiconductor-based photocatalysts with extremely low precious metal content to reduce the catalyst cost while achieving good activity.

Amino‐Assisted Anchoring of CsPbBr3 Perovskite Quantum Dots on Porous g‐C3N4 for Enhanced Photocatalytic CO2 Reduction

Halide perovskite quantum dots (QDs) have great potential in photocatalytic applications if their low charge transportation efficiency and chemical instability can be overcome. To circumvent these obstacles, we anchored CsPbBr3 QDs (CPB) on NHx -rich porous g-C3 N4 nanosheets (PCN) to construct the composite photocatalysts via N-Br chemical bonding. The 20 CPB-PCN (20 wt % of QDs) photocatalyst exhibits good stability and an outstanding yield of 149 μmol h-1  g-1 in acetonitrile/water for photocatalytic reduction of CO2 to CO under visible light irradiation, which is around 15 times higher than that of CsPbBr3 QDs. This study opens up new possibilities of using halide perovskite QDs for photocatalytic application.