Electronic structure greatly determines the band structures and the charge carrier transport properties of semiconducting photocatalysts and consequently their photocatalytic activities. Here, by simply calcining the mixture of graphitic carbon nitride (g-C3 N4 ) and sodium borohydride in an inert atmosphere, boron dopants and nitrogen defects are simultaneously introduced into g-C3 N4 . The resultant boron-doped and nitrogen-deficient g-C3 N4 exhibits excellent activity for photocatalytic oxygen evolution, with highest oxygen evolution rate reaching 561.2 µmol h-1 g-1 , much higher than previously reported g-C3 N4 . It is well evidenced that with conduction and valence band positions substantially and continuously tuned by the simultaneous introduction of boron dopants and nitrogen defects into g-C3 N4 , the band structures are exceptionally modulated for both effective optical absorption in visible light and much increased driving force for water oxidation. Moreover, the engineered electronic structure creates abundant unsaturated sites and induces strong interlayer C-N interaction, leading to efficient electron excitation and accelerated charge transport. In the present work, a facile approach is successfully demonstrated to engineer the electronic structures and the band structures of g-C3 N4 with simultaneous introduction of dopants and defects for high-performance photocatalytic oxygen evolution, which can provide informative principles for the design of efficient photocatalysis systems for solar energy conversion.

Synergy of Dopants and Defects in Graphitic Carbon Nitride with Exceptionally Modulated Band Structures for Efficient Photocatalytic Oxygen Evolution.

Due to the growing demand for energy and impending environmental issues, fuel cells have attracted significant attention as an alternative to conventional energy technologies. As cost is the main inhibitor of this technology, low cost catalysts with high activity and stable catalytic performance are the key to large scale application of fuel cells. The development and recent advancements of Pt and Pt-based electrocatalysts are discussed in this review. Discussion is mainly focused on the structure and composition of Pt and Pt-based electrocatalysts, which significantly affect the catalytic activities and durability of fuel cell catalysts. The electrocatalysts including Pt single metal, Pt-based alloys (including noble alloys, non-noble alloys, metal oxide alloys, and non-metal alloys), and structure-controlled alloys (nanopolyhedra, nanodendrites, and hollow and core–shell structures) were discussed. The activity, stability, and efficiency of Pt and Pt-based catalysts for both the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) as well as the correlation between the catalytic performance, structure optimization, and composition modulation of catalysts are also discussed.

Current progress of Pt and Pt-based electrocatalysts used for fuel cells

CO2 electroreduction reaction (CO2RR) to fuels and feedstocks is an attractive route to close the anthropogenic carbon cycle and store renewable energy. The generation of more reduced chemicals, especially multicarbon oxygenate and hydrocarbon products (C2+) with higher energy density is highly desirable for industrial applications. However, selective conversion of CO2 to C2+ suffers from high overpotential, low reaction rate and low selectivity, and the process is extremely sensitive to the catalyst structure and electrolyte. Here we discuss strategies to achieve high C2+ selectivity through rational design of the catalyst and electrolyte. Current state-of-the-art catalysts, including Cu and Cu-bimetallic catalysts as well as alternative materials are considered. The importance of taking into consideration the dynamic evolution of the catalyst structure and composition are highlighted, focusing on findings extracted from in situ and operando characterizations. Additional theoretical insight into the reaction mechanisms underlying the improved C2+ selectivity of specific catalyst geometries/compositions in synergy with a well-chosen electrolyte are also provided.

Rational Catalyst and Electrolyte Design for Co2 Electroreduction Towards Multicarbon Products

The study of hydrogen evolution reaction and oxygen evolution reaction electrocatalysts for water electrolysis is a developing field in which noble metal-based materials are commonly used. However, the associated high cost and low abundance of noble metals limit their practical application. Non-noble metal catalysts, aside from being inexpensive, highly abundant and environmental friendly, can possess high electrical conductivity, good structural tunability and comparable electrocatalytic performances to state-of-the-art noble metals, particularly in alkaline media, making them desirable candidates to reduce or replace noble metals as promising electrocatalysts for water electrolysis. This article will review and provide an overview of the fundamental knowledge related to water electrolysis with a focus on the development and progress of non-noble metal-based electrocatalysts in alkaline, polymer exchange membrane and solid oxide electrolysis. A critical analysis of the various catalysts currently available is also provided with discussions on current challenges and future perspectives. In addition, to facilitate future research and development, several possible research directions to overcome these challenges are provided in this article.

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Recent Progresses in Electrocatalysts for Water Electrolysis

The conversion of carbon dioxide (CO2) into fuels and valuable chemicals using solar energy is a promising method for reducing CO2 emissions and solving energy supply issues. However, the development of inexpensive, efficient and metal-free materials for photocatalytic CO2 reduction is challenging. Herein, we report a facile supramolecular self-assembly strategy for the preparation of porous nitrogen-rich graphitic carbon nitride (g-C3N4) nanotubes with Lewis basicity and a large surface area, which are beneficial for the adsorption of CO2 and, consequently, the enhancement of the photocatalytic CO2 reduction activity. The metal-free porous nitrogen-rich g-C3N4 nanotubes catalyst exhibits a superior visible-light-induced CO2-to-CO conversion rate of 103.6 μmol g−1 h−1, which is 17 and 15 times higher than those of bulk g-C3N4 (6.1 μmol g−1 h−1) and P25-TiO2 (7.1 μmol g−1 h−1), respectively, and exceeds the performance of most metal-free photocatalysts. This work provides new insights into the synthesis of functional groups-modified g-C3N4 with a unique structure for effective photocatalytic CO2 reduction.

Porous nitrogen-rich g-C3N4 nanotubes for efficient photocatalytic CO2 reduction

It is still a great challenge to achieve high selectivity of CH4 in CO2 electroreduction reactions (CO2 RR) because of the similar reduction potentials of possible products and the sluggish kinetics for CO2 activation. Stabilizing key reaction intermediates by single type of active sites supported on porous conductive material is crucial to achieve high selectivity for single product such as CH4 . Here, Cu2 O(111) quantum dots with an average size of 3.5 nm are in situ synthesized on a porous conductive copper-based metal-organic framework (CuHHTP), exhibiting high selectivity of 73 % towards CH4 with partial current density of 10.8 mA cm-2 at -1.4 V vs. RHE (reversible hydrogen electrode) in CO2 RR. Operando infrared spectroscopy and DFT calculations reveal that the key intermediates (such as *CH2 O and *OCH3 ) involved in the pathway of CH4 formation are stabilized by the single active Cu2 O(111) and hydrogen bonding, thus generating CH4 instead of CO.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/anie.202085262

Highly Selective CO 2 Electroreduction to CH 4 by In Situ Generated Cu 2 O Single-Type Sites on a Conductive MOF: Stabilizing Key Intermediates with Hydrogen Bonding

Carbon-based catalysts have demonstrated great potential for the aerobic oxidative dehydrogenation reaction (ODH) However, its widespread application is retarded by the unavoidable deactivation owing to the appearance of coking or combustion under ODH conditions The synthesis and characterization of porous structure of BCN nanosheets as well as their application as a novel catalyst for ODH is reported Such BCN nanosheets consist of hybridized, randomly distributed domains of h-BN and C phases, where C, B, and N were confirmed to covalent bond in the graphene-like layers Our studies reveal that BCN exhibits both high activity and selectivity in oxidative dehydrogenation of ethylbenzene to styrene, as well as excellent oxidation resistance The discovery of such a simple chemical process to synthesize highly active BCN allows the possibility of carbocatalysis to be explored

Carbon-Doped BN Nanosheets for the Oxidative Dehydrogenation of Ethylbenzene.

Efficient co-catalysts are crucial for photocatalytic water oxidation towards conversion of solar energy into chemical energy. Herein, we develop a sustainable and effective water oxidation system using graphitic carbon nitride (g-C3N4) and cubic cobalt manganese spinel (c-CoMn2O4) as light transducer and water oxidation co-catalyst, respectively. The surface modified g-C3N4 with c-CoMn2O4 not only accelerates the interface transfer rate of charge carriers but also reduces the excessive energy barrier for O O formation, leading to an enhanced photocatalytic activity of water oxidation. Benefiting from the well surface engineering of g-C3N4, the g-C3N4-CoMn2O4 (CN-CM) composites exhibit an enhanced performance of photocatalytic water oxidation. The oxygen evolution rate (OER) of CN-CM is 4 times higher than that of pristine g-C3N4. It is a highly active in oxidation of water, with an apparent quantum yield (AQY) of ca. 1% at 380 nm with AgNO3 as sacrificial agent. This improvement is mainly due to the mixed-valence Co and Mn cations contained in c-CoMn2O4 spinel.

Cobalt manganese spinel as an effective cocatalyst for photocatalytic water oxidation

Fabrication of highly active carbon-supported atomically isolated metal catalysts with maximized atomic efficiency is significant but remains a big challenge because the adjacent metal species are ...

Zai-Lai Xie

Papers

Highly Selective CO 2 Electroreduction to CH 4 by In Situ Generated Cu 2 O Single-Type Sites on a Conductive MOF: Stabilizing Key Intermediates with Hydrogen Bonding

Carbon-Doped BN Nanosheets for the Oxidative Dehydrogenation of Ethylbenzene.

Cobalt manganese spinel as an effective cocatalyst for photocatalytic water oxidation

Spatial Sites Separation Strategy to Fabricate Atomically Isolated Nickel Catalysts for Efficient CO2 Electroreduction