Electrochemical fixation of N2 to ammonia is a promising strategy to store renewable energy and mitigate greenhouse gas emissions. However, it usually suffers from extremely low ammonia yield and Faradaic efficiency because of the lack of efficient electrocatalysts and the competing hydrogen evolution reaction. Herein, we report that the semiconducting bismuth can be a promising catalyst for ambient electrocatalytic N2 reduction reaction (NRR). A two-dimensional mosaic bismuth nanosheet (Bi NS) was fabricated via an in situ electrochemical reduction process and exhibited favorable average ammonia yield and Faradaic efficiency as high as 2.54 ± 0.16 μgNH3 cm–2 h–1 (∼13.23 μg mgcat. –1 h–1) and 10.46 ± 1.45% at −0.8 V versus reversible hydrogen electrode in 0.1 M Na2SO4. The high NRR electrocatalytic activity of the Bi NS could be attributed to the sufficient exposure of edge sites coupled with effective p-orbital electron delocalization in the mosaic bismuth nanosheets. In addition, the semiconducting feature, which limits surface electron accessibility, could effectively enhance the Faradaic efficiency. This work highlights the potential importance of less reactive main group elements with tunable p-electron density, semiconducting property, and ingenious nanostructure for further exploration of N2 reduction reaction electrocatalysts.

The electrochemical reduction of O2 via a two‐electron reaction pathway to H2O2 provides a possibility for replacing the current anthraquinone process, enabling sustainable and decentralized H2O2 production. Here, a nitrogen‐rich few‐layered graphene (N‐FLG) with a tunable nitrogen configuration is developed for electrochemical H2O2 generation. A positive correlation between the content of pyrrolic‐N and the H2O2 selectivity is experimentally observed. The critical role of pyrrolic‐N is elucidated by the variable intermediate adsorption profiles as well as the dependent negative shifts of the pyrrolic‐N peak on X‐ray adsorption near edge structure spectra. By virtue of the optimized N doping configuration and the unique porous structure, the as‐fabricated N‐FLG electrocatalyst exhibits high selectivity toward electrochemical H2O2 synthesis as well as superior long‐term stability. To achieve high‐value products on both the anode and cathode with optimized energy efficiency, a practical device coupling electrochemical H2O2 generation and furfural oxidation is assembled, simultaneously enabling a high yield rate of H2O2 at the cathode (9.66 mol h−1 gcat−1) and 2‐furoic acid at the anode (2.076 mol m−2 h−1) under a small cell voltage of 1.8 V.

Photocatalytic CO2 reduction is an effective means to generate renewable energy. It involves redox reactions, reduction of CO2 and oxidation of water, that leads to the production of solar fuel. Significant research effort has therefore been made to develop inexpensive and practically sustainable semiconductor‐based photocatalysts. The exploration of atomic‐level active sites on the surface of semiconductors can result in an improved understanding of the mechanism of CO2 photoreduction. This can be applied to the design and synthesis of efficient photocatalysts. In this review, atomic‐level reactive sites are classified into four types: vacancies, single atoms, surface functional groups, and frustrated Lewis pairs (FLPs). These different photocatalytic reactive sites are shown to have varied affinity to reactants, intermediates, and products. This changes pathways for CO2 reduction and significantly impacts catalytic activity and selectivity. The design of a photocatalyst from an atomic‐level perspective can therefore be used to maximize atomic utilization efficiency and lead to a high selectivity. The prospects for fabrication of effective photocatalysts based on an in‐depth understanding are highlighted.

The electrochemical nitrogen reduction reaction (NRR) is a promising alternative to the energy‐intensive Haber–Bosch process for ammonia synthesis. Among the possible electrocatalysts, bismuth‐based materials have shown unique NRR properties due to their electronic structures and poor hydrogen evolution activity. However, identification of the active sites and reaction mechanism is still difficult due to structural and chemical changes under reaction potentials. Herein, in situ Raman spectroscopy, complemented by electron microscopy, is employed to investigate the structural and chemical transformation of the Bi species during the NRR. Nanorod‐like bismuth‐based metal–organic frameworks are reduced in situ and fragment into densely contacted Bi0 nanoparticles under the applied potentials. The fragmented Bi0 nanoparticles exhibit excellent NRR performance in both neutral and acidic electrolytes, with an ammonia yield of 3.25 ± 0 .08 µg cm−2 h−1 at −0.7 V versus reversible hydrogen electrode and a Faradaic efficiency of 12.11 ± 0.84% at −0.6 V in 0.10 m Na2SO4. Online differential electrochemical mass spectrometry detects the production of NH3 and N2H2 during NRR, suggesting a possible pathway through two‐step reduction and decomposition. This work highlights the importance of monitoring and optimizing the electronic and geometric structures of the electrocatalysts under NRR conditions.

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The conversion of water into clean hydrogen fuel using renewable solar energy can potentially be used to address global energy and environmental issues. However, semiconductorbased photocatalytic H 2 evolution from pure water splitting has low efficiency and poor stability. Hole scavengers are therefore added to boost separation efficiency of photo-excited electron-hole pairs and improve stability by consuming the strongly oxidative photo-excited holes. The drawbacks of this approach are an increased cost and production of waste. Recently, researchers have reported the use of abundantly available hole scavengers, including biomass, biomass-derived intermediates, plastic wastes, and a range of alcohols for H 2 evolution, coupled with value-added chemicals production using semiconductor-based photocatalysts. It is timely, therefore, to comprehensively summarize the properties, performances, and mechanisms of these photocatalysts, and critically review recent advances, challenges and opportunities in this emerging area. Herein, this paper: 1) outlines fundamental reaction mechanisms of photocatalysts for H 2 evolution coupled with selective oxidation, C-H activation and CC coupling, together with non-selective oxidation, using holescavengers; 2) introduces equations to compute conversion/selectivity of selective oxidation; 3) summarizes and critically compares recently reported photocatalysts with particular emphasis on correlation between physicochemical characteristics and performances, together with photocatalytic mechanisms, and; 4) appraises current advances and challenges.

Single-atom photocatalysts have demonstrated an enormous potential in producing value-added chemicals and/or fuels using sustainable and clean solar light to replace fossil fuels causing global energy and environmental issues. These photocatalysts not only exhibit outstanding activities, selectivity, and stabilities due to their distinct electronic structures and unsaturated coordination centers but also tremendously reduce the consumption of catalytic metals owing to the atomic dispersion of catalytic species. Besides, the single-atom active sites facilitate the elucidation of reaction mechanisms and understanding of the structure-performance relationships. Presently, apart from the well-known reactions (H2 production, N2 fixation, and CO2 conversion), various novel reactions are successfully catalyzed by single-atom photocatalysts possessing high efficiency, selectivity, and stability. In this contribution, we summarize and discuss the design and fabrication of single-atom photocatalysts for three different kinds of emerging reactions (i.e., reduction reactions, oxidation reactions, as well as redox reactions) to generate desirable chemicals and/or fuels. The relationships between the composition/structure of single-atom photocatalysts and their activity/selectivity/stability are explained in detail. Additionally, the insightful reaction mechanisms of single-atom photocatalysts are also introduced. Finally, we propose the possible opportunities in this area for the design and fabrication of brand-new high-performance single-atom photocatalysts.

continually intensified and could be out of control. Therefore, it is urgent to greatly reduce the gigantic consumption of carbonbased fossil fuels, [1,2] which emit substantial greenhouse gases and tremendously aggravate global warming. Furthermore, it is of great significance to realize carbon neutrality in human society via replacing fossil fuels with low-carbon/carbon-free alternatives. Thus, the conversion of renewable solar energy [3][4][5] into clean and carbonfree hydrogen (H 2 ) fuel is highly attractive. Such a solar-to-H 2 (STH) conversion can be achieved utilizing photocatalytic H 2 evolution via water splitting, [6][7][8][9][10] which is regarded as an alluring, environmentally benign and low-cost strategy. Hence, a highly active, robust, and affordable photocatalyst is the most sought after. [11][12][13] The rational design and synthesis of such a photocatalyst require not only the emerging nanosized building blocks with desired features, but also efficient charge dissociation/ transfer boosted by the strong built-in electric field in a favorable junction system.In the past decades, 2D materials have demonstrated great capacity to achieve efficient and cost-effective photocatalysis for various reactions, due to their distinct physicochemical features. [14][15][16][17][18][19][20][21] Recently, an emerging 2D material, FePS 3 (FPS), [22][23][24][25][26][27] has displayed numerous attractive characteristics for catalysis: i) Ultrathin structure facilitating rapid bulkto-surface electron-hole transport; ii) high specific surface area accelerating efficient adsorption/desorption of reactant and product, and benefiting the anchoring of other nanobuilding blocks; iii) exposed under-coordinated edge atoms serving as active sites to advance the reactions; iv) thicknessdependent electronic band structure promoting the regulation of light absorption and redox abilities of charge carriers; v) p-type semiconductor nature favoring the construction of certain junction system with a strong built-in electric field. Albeit the above alluring advantages, [28][29][30] only a few works reported the application of FPS in photocatalysis. For instance, FPS quantum sheets show the photocatalytic H 2 -evolution rate of 290 µmol h −1 g −1 in 10% triethanolamine aqueous solution under xenon light illumination. [28] Porous FPS nanosheets exhibit the photocatalytic H 2 -evolution activity of 305.6 µmol h −1 g −1 in 10% triethylamine aqueous solution with xenon light irradiation. [29] Nevertheless, to the best of our The aggravating extreme climate changes and natural disasters stimulate the exploration of low-carbon/zero-carbon alternatives to traditional carbonbased fossil fuels. Solar-to-hydrogen (STH) transformation is considered as appealing route to convert renewable solar energy into carbon-free hydrogen. Restricted by the low efficiency and high cost of noble metal cocatalysts, high-performance and cost-effective photocatalysts are required to realize the realistic STH transformation. Herein, the 2D FePS 3 (FPS) nanoshee...