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It is significant to develop low-cost and highly efficient electrocatalysts for the hydrogen evolution reaction (HER) via electrochemical water splitting. Herein, we constructed P-doped NiCo2S4 nanowire arrays on carbon fiber paper (NiCo2S4−xPx/CFP) as a HER electrocatalyst in both acidic and alkaline media. Benefitting from P doping into NiCo2S4, the as-prepared NiCo2S4−xPx/CFP exhibits low HER overpotentials of 80 and 132 mV in acidic and alkaline media at a cathodic current density of 10 mA cm−2, respectively, which are far superior to counterparts of NiCo2S4 nanowire arrays on the carbon fiber paper (NiCo2S4/CFP). Meanwhile, the NiCo2S4−xPx/CFP presents excellent HER stability of 20 hours in acidic and alkaline media. From the results of density functional theory calculations, P doping can not only optimize the hydrogen adsorption energetics on each kind of atomic site of catalysts, but also strengthen the H2O molecule binding ability on the catalyst surface for the alkaline HER and favor kinetics of hydrogen adsorption and H2 formation on the catalyst surface for the acidic HER, eventually improving overall HER performances. The investigation of the HER mechanism modulated by P doping in our work offers novel inspiration to develop highly efficient ternary metal sulfides for the HER. [ABSTRACT FROM AUTHOR]

Cocatalysts are usually applied in the photocatalytic water splitting process to accelerate the kinetics of the hydrogen evolution reaction (HER). Specifically, the transition metal nitride (Mo2N) featuring a unique local surface plasmon resonance (LSPR) effect has exhibited great potential to function as a HER cocatalyst. However, the low metallicity of Mo2N hampers its ability to improve charge separation. To address this issue, transition metal atom doping (Co and Cu) engineering was used to modulate the electronic structure of Mo2N nanosheets to achieve a higher electrical conductivity and a lower hydrogen adsorption free energy (‖ΔGH*‖), thereby favoring the HER kinetics. Density functional theory (DFT) calculations and experimental results showed that Co-doping and Cu-doping mainly take place at Mo sites in the crystal structure of Mo2N to form stable structures of Co doped Mo2N (Co–Mo2N) and Cu doped Mo2N (Cu–Mo2N). Compared with pristine Mo2N, both Cu–Mo2N and Co–Mo2N demonstrated a much improved cocatalytic effect over g-C3N4 in promoting charge separation, accelerating HER kinetics and enhancing light absorption. The Co–Mo2N with the highest conductivity and lowest ‖ΔGH*‖ illustrated the best cocatalytic effect, and the H2 production performance (367.8 μmol g−1 h−1) of Co–Mo2N/g-C3N4 achieved was 10 and 5 times higher than those of Mo2N/g-C3N4 and Cu–Mo2N/g-C3N4. This paper provides significant guidance in the design and development of efficient cocatalysts for the HER application. [ABSTRACT FROM AUTHOR]

Porphyrins have been widely used in designing photocatalyst systems. However, finding an effective strategy to improve the intrinsic photocatalytic activity of porphyrin molecules remains a challenge. Here, two new porphyrins, meso-tetra(5-carboxyfuryl)porphyrin (H2TCFP) and meso-tetra(5-carboxythienyl)porphyrin (H2TCTP), were successfully synthesized and compared with meso-tetra(m-carboxyphenyl)porphyrin (H2TmCPP), to clarify the influence of the organic unit bridging the carboxyl acid group with the porphine ring on the photocatalytic activity of porphyrin for H2 evolution from water splitting. The H2 evolution rates of 10.8 mmol g−1 h−1 observed for H2TCFP and 9.7 mmol g−1 h−1 for H2TCTP are both larger than 8.0 mmol g−1 h−1 observed for H2TmCTP under optimal conditions. The best photocatalytic activity observed for H2TCFP was investigated through experiments and density functional theory (DFT) calculations and was interpreted in terms of the combined effect of several key factors of the entire photocatalytic process, including the high absorptivity of UV light, high separation efficiency of photogenerated carriers, and low Gibbs energy required for associated water splitting. Meanwhile, the concentration-dependent performance of photocatalytic activity was analyzed and attributed to the aggregation and light-bleaching effect exerted on porphyrins. [ABSTRACT FROM AUTHOR]

MoSe2 as one graphene-like 2D transition metal selenide has attracted great attention. However, its application for the hydrogen evolution reaction (HER) is still restricted by the poor electrical conductivity and structural restacking. In this work, an excellent electrocatalyst for hydrogen production is developed based on the in situ synthesis of V-doped MoSe2 confined on carbon black nanoparticles (denoted as V-MoSe2/CB) via a sol–gel process. The characterization results show that the carbon black nanoparticles can protect the V-MoSe2 nanosheets from agglomeration, resulting in ultra-thin thickness and short vertical lattice arrays. Meanwhile, density functional theory (DFT) calculations indicate that vanadium doping can optimize the electronic structure of MoSe2. Accordingly, compared to the pure MoSe2, V-MoSe2 and MoSe2/CB electrocatalysts, V-MoSe2/CB exhibits improved electrocatalytic activity with a small overpotential of 166 mV at −10 mA cm−2 and a small Tafel slope of 65 mV dec−1. This work paves a new way for improving the HER performance through synergistic morphology, structure and electronic regulation. [ABSTRACT FROM AUTHOR]

The design of low-cost and high-performance bifunctional catalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is of great significance for overall water splitting. Herein, RuNi single atom alloy (SAA) decorated on reduced graphene oxide (RuNi@rGO) was synthesized by a facile strategy for use as a bifunctional HER/OER catalyst. The as-obtained RuNi@rGO catalyst exhibits outstanding electrocatalytic activities with an ultralow overpotential for the HER (15 mV) and the OER (240 mV) at a current density of 10 mA cm−2. Density functional theory (DFT) calculations demonstrate that the introduction of Ru single atoms can evidently change the electron distribution and coordination environment around Ni, and reduce the intermediate's adsorption free energy of RuNi@rGO, thus facilitating the HER/OER catalytic rate. Moreover, when used as the cathode and anode of a two-electrode system, the RuNi@rGO-based water splitting device exhibits a low potential of 1.52 V at a current density of 10 mA cm−2, as well as a high faradaic efficiency almost up to 100%, making RuNi@rGO bifunctional electrocatalysts attractive for energy storage and conversion. [ABSTRACT FROM AUTHOR]

The electrocatalytic CO2 reduction reaction (CO2RR) offers a fascinating approach to converting CO2 into valuable chemical feedstocks. Up to now, the development of highly efficient electrocatalysts has been a significant bottleneck in this field. In this study, employing density functional theory (DFT) calculations, we design a range of stable two-dimensional (2D) metalloporphyrin organic frameworks (TM-PMOFs, TM = Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, and Ag, respectively) built by copper clusters and metalloporphyrin (TM-TCPP), whose CO2RR performance is studied in detail. Among them, the 2D cobaltporphyrin-based organic framework (Co-PMOF) is identified to be the best CO2RR electrocatalyst on account of its low limiting potential (−0.53 V), whose enhanced electrocatalytic performance can be attributed to the presence of numerous active sites on both sides of its 2D framework, as well as the synergistic effect between copper clusters and cobaltporphyrins in facilitating CO2 reduction. These findings provide valuable insights and encourage further experimental research on metallic 2D PMOF materials for CO2 electrochemical reduction. [ABSTRACT FROM AUTHOR]

Black phosphorene (BP) is a metal-free two-dimensional photocatalyst with potential for visible-light-driven photocatalytic H2 evolution. However, its inert basal plane toward the HER hinders its practical application. To overcome this problem, we design a novel nonprecious metal–nonmetal co-doping method of BP to activate its inert basal plane and improve photocatalytic HER performance. Through density functional theory (DFT) calculations, we systematically investigate the photocatalytic performance of nonprecious metal and nonmetal co-doped BPs. Our results show that V–N co-doped BP exhibits excellent thermodynamic stability, suitable band structure, improved carrier separation, superior adsorption and dissociation energies and enhanced visible-light absorption coefficient. Importantly, V–N co-doping successfully activates the inert basal plane of BP, allowing it to drive the HER under illumination (ΔGH = −0.12 eV). This study highlights the potential of nonprecious metal–nonmetal co-doping to enhance the photocatalytic activity of BP, providing invaluable insights for advancing the field of co-doped BP in photocatalysis. [ABSTRACT FROM AUTHOR]

Covalent triazine frameworks (CTFs) involving donor-π bridge-acceptor (D–π–A) motifs with the electron-withdrawing triazine unit as the acceptor have been regarded as one of the most promising materials for photocatalytic water splitting. The intrinsic features of π-bridges play a critical role in tailoring the polymer properties as well as the photocatalytic performance. Introducing suitable conjugated units as the π-bridge is expected to effectively tune the electronic structure of the resultant D–π–A CTFs and facilitate photo-generated charge separation. However, systematic studies on how different π-bridges would influence the photoelectronic properties of D–π–A type CTFs are still limited. Herein, three types of CTFs with well-defined D–π–A structures named Ben-CTF, BenT-CTF and BenP-CTF were synthesized to investigate the effects of different π-bridges (benzene, thiophene and pyridine units) on the performance of photocatalytic water splitting for hydrogen production. Comprehensive experiments and density functional theory (DFT) calculations revealed that BenP-CTF with the pyridine unit as the π-bridge exhibited superior charge migration ability and higher photocatalytic hydrogen evolution reaction (HER) rates compared to the other CTFs. This work may provide a reference for the rational design and controllable synthesis of CTF materials for efficient photocatalysis. [ABSTRACT FROM AUTHOR]

Focusing on renewable energy, we developed an efficient and robust catalyst for overall water splitting (OWS). Using density functional theory (DFT) as the guide, a combination electrode with bifunctional activities based on Co-based carbonate hydroxides (CCHs) and pyrenely-graphdiyne nanowalls (Pyr-GDY-NWs) with three-dimensional structures was designed, and then a series of experiments were attempted to prepare the combination electrode CCH@Pyr-GDY-NWs. From the data of theory and experiment, we found that the combination electrode CCH@Pyr-GDY-NWs exhibits an outstanding catalytic activity towards OWS. The design approach reported herein could open up a new avenue for the construction of three-dimensional Pyr-GDY-NW-based electrodes with high catalytic activity. [ABSTRACT FROM AUTHOR]

Single-atom catalysis is a new field that has developed rapidly in recent years and has greatly helped the development of catalytic science. We have processed a large amount of literature data through the Web of Science database. The bibliometric method was used to analyze the development trend and research hotspots over the past 10 years since the concept of single-atom catalysis was proposed in 2011. Results show that the field of single-atom catalysis is currently at a high-speed development stage. China is in a leading position in terms of comprehensive strength, with the largest number of publications and great influence. Most productive journals and institutions are ACS Catalysis and Chinese Acad. Sci. Single-atom catalysis has the most research results in the field of chemistry. In addition, the most commonly used keywords are "density functional theory", "oxygen reduction reaction", "electrocatalysis", "co oxidation", "graphene", "heterogeneous catalysis", "platinum", "hydrogen evolution reaction", which reflect the research direction of the current field. This article reviews the main research content of single-atom catalysts in order to facilitate researchers understanding the current situation in the field, and to also provide some guidance for future research. [ABSTRACT FROM AUTHOR]

The development of earth-rich, low-cost, and high-efficiency electrocatalysts toward alkaline hydrogen evolution reactions (HERs) in the water spitting process is extremely desirable yet a huge challenge. In this work, we report the synthesis of novel RuO2/MoS2 electrocatalysts with good conductivity and abundant active sites for efficient HER by uniformly dispersing RuO2 nanoparticles on MoS2 nanosheets. Benefitting from the intense electronic coupling effect endowed with interface modifications, the as-prepared RuO2/MoS2 electrocatalysts exhibited superior performance for HER in 1 M KOH with a very low overpotential of 36 mV at 10 mA cm−2 and a small Tafel slope value of 34.8 mV dec−1. Moreover, the introduction of RuO2 nanoparticles improved the durability of the RuO2/MoS2 electrocatalysts with negligible variation in a 20 h operation. More importantly, the density functional theory (DFT) calculations further revealed the mechanism of strong electronic interaction between RuO2 nanoparticles and MoS2 nanosheets, which contributes to accelerating the H2O dissociation kinetics and optimizing H adsorption Gibbs free energy. This work may provide a deeper understanding for designing efficient HER catalysts through interface modification strategies. [ABSTRACT FROM AUTHOR]

The development of substantial, environment-friendly and low-cost electrocatalysts for an efficient oxygen reduction reaction (ORR) is essentially important for the production and storage of green energy which has sparked the curiosity of researchers for scalable production of metal-free electrocatalysts from biowaste. We report an easy transformation of chestnut-derived biowaste into reduced graphene oxide (rGO) and pyridinic-N-dominated nitrogen-doped rGO (NCS-rGO). The synthesized catalyst exhibits better ORR activity with an onset and half-wave potential of 0.93 V and 0.86 V, respectively, along with a high diffusion-limiting current density of 5.05 mA cm−2. Under alkaline conditions, we found that NCS-rGO shows an unusually high electrocatalytic activity that is superior to that of the commercial 20% Pt/C catalyst. More notably, the NCS-rGO-based ORR electrocatalyst manifests higher methanol tolerance, without deterioration in catalytic activity even in the presence of significant amount of methanol, outperforming the current state-of-the-art Pt electrocatalyst. Density functional theory (DFT) studies illustrate that pyridinic N is a decisive part of NCS-rGO to achieve the best ORR performance. [ABSTRACT FROM AUTHOR]

Cocatalysts are usually applied in the photocatalytic water splitting process to accelerate the kinetics of the hydrogen evolution reaction (HER). Specifically, the transition metal nitride (Mo2N) featuring a unique local surface plasmon resonance (LSPR) effect has exhibited great potential to function as a HER cocatalyst. However, the low metallicity of Mo2N hampers its ability to improve charge separation. To address this issue, transition metal atom doping (Co and Cu) engineering was used to modulate the electronic structure of Mo2N nanosheets to achieve a higher electrical conductivity and a lower hydrogen adsorption free energy (‖ΔGH*‖), thereby favoring the HER kinetics. Density functional theory (DFT) calculations and experimental results showed that Co-doping and Cu-doping mainly take place at Mo sites in the crystal structure of Mo2N to form stable structures of Co doped Mo2N (Co–Mo2N) and Cu doped Mo2N (Cu–Mo2N). Compared with pristine Mo2N, both Cu–Mo2N and Co–Mo2N demonstrated a much improved cocatalytic effect over g-C3N4 in promoting charge separation, accelerating HER kinetics and enhancing light absorption. The Co–Mo2N with the highest conductivity and lowest ‖ΔGH*‖ illustrated the best cocatalytic effect, and the H2 production performance (367.8 μmol g−1 h−1) of Co–Mo2N/g-C3N4 achieved was 10 and 5 times higher than those of Mo2N/g-C3N4 and Cu–Mo2N/g-C3N4. This paper provides significant guidance in the design and development of efficient cocatalysts for the HER application. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS2)-based transition-metal chalcogenides are considered to be cost-efficient, environmentally-friendly, and stable materials in the application of electrocatalytic hydrogen production. However, the low density and poor reactivity of active sites within the basal plane of MoS2 hinder hydrogen evolution reaction (HER). Herein, we reported that N, P co-doped in the basal plane of MoS2 (N, P-MoS2) can convert the parts of 2H MoS2 to 1T MoS2 and enlarge interlayer spacing for an efficient HER. Subsequently, electrochemical tests revealed that N, P-MoS2 showed an overpotential of 179 mV at 10 mA cm−2, a corresponding Tafel slope of 143 mV dec−1, and remarkable long-term stability over 20 h. In addition, we combined these findings with theoretical results from density functional theory (DFT) simulations. The results confirmed that the synergistic effect of N and P activated the HER catalytic activity at the edge of N-MoS2. In short, the synergy improved the conductivity of N-MoS2 and promoted the rapid transfer of charge to achieve high-performance HER activity. The work provides new insight into the synergistic effect of N and P co-doped in the basal plane of MoS2, as well as a new pathway for the rational design of efficient HER electrocatalysts. [ABSTRACT FROM AUTHOR]

We present here the influence of different surface terminations on the electronic, optical, and photocatalytic properties of trans and cis BaTaO2N using density functional theory calculations. For each surface, we consider two complementary terminations exposed with Ba and Ta atoms, respectively. The calculated surface energies suggest that (001) and (100) are more stable than other low-index surfaces. Work functions are distinct for various surface terminations, which can be attributed to the atomic displacements in different directions and degrees after relaxation. We propose that the transferring direction of the photogenerated carriers in BaTaO2N-based heterostructures could be controlled by obtaining the preferred surface termination. The simulated absorption spectra suggest that both trans and cis BaTaO2N exhibit optical anisotropy, which could result from the difference in relaxed crystal parameters along different directions. Dissociative water adsorption on both the (001) and (100) terminations is thermodynamically favorable. The hydrogen evolution reaction (HER) is easier to occur on the terminations exposed with Ta, O, and N simultaneously. The computed overpotentials of oxygen evolution reaction (OER) for trans-(001)-BaO, cis-(001)-TaON, cis-(001)-BaO, and cis-(100)-Ta2O3N are in good agreement with the experimental results. These findings provide important insights into the rational design of (001)- and (100)-oriented BaTaO2N samples for enhanced photocatalytic activity. [ABSTRACT FROM AUTHOR]

The approach of artificial photosynthesis involves the use of water and sunlight to achieve the photoreduction of CO2 into carbohydrates. Herein, the GaSe monolayer is investigated in terms of its structural, electronic and photocatalytic properties via first-principles calculations towards water splitting and artificial photosynthesis. The mechanical and dynamical stability of the GaSe monolayer was affirmed according to the Born–Huang mechanical stability conditions and phonon band structure, respectively. The GaSe monolayer has an indirect bandgap value of 2.92 eV, with band edges that straddle the water redox and CO2 reduction potentials. Consequently, the GaSe monolayer is a potential photocatalyst for water splitting and CO2 photoreduction over a wide pH range of 0–14. Moreover, a high electron and hole mobility was obtained, which is more significant compared to a 2D MoS2 monolayer. To improve its photocatalytic performance, the GaSe monolayer was investigated in-depth under biaxial tensile and compressive strain. Interestingly, the optimum strain values for water splitting and CO2 photoreductions are 5% and 4%, respectively, owing to their band edges in the vicinity of the redox potentials. Moreover, the GaSe monolayer under 3% tensile strain has a Gibb's free energy for hydrogen adsorption (ΔGH) value of close to 0 eV, making it a promising photocatalyst for hydrogen evolution reaction (HER) activity. Moreover, the strain-induced monolayers have absorption coefficients on the order of 105 cm−1, making the material a potential candidate for solar energy harvesting. Our study suggests that the effect of biaxial strain on these types of transition metal monochalcogenides can be explored experimentally to develop an excellent photocatalyst for use in photocatalytic water splitting and artificial photosynthesis applications. [ABSTRACT FROM AUTHOR]

Producing molecular hydrogen (H2) using water provides a sustainable approach for developing clean energy technologies. Herein, we report highly active ruthenium (Ru) clusters supported on iron oxide (Ru/Fe3O4) and Fe3O4/multi-walled carbon nanotubes (Ru/Fe3O4/MWCNTs) by simple electrochemical deposition in a neutral aqueous medium. The supported catalyst exhibits good hydrogen evolution reaction (HER) activity in an acidic environment. Cyclic voltammograms (CVs) of potassium ferrocyanide (K4[Fe(CN)6]) confirm that MWCNTs enhance the electron transfer process by decreasing the redox formal potential. The overpotentials of Ru/Fe3O4/MWCNTs and Ru/Fe3O4 electrocatalysts versus the reversible hydrogen electrode (RHE) were found to be 101 mV and 306 mV to reach a current density of 10 mA cm−2. As prepared, the catalyst displays good stability and retain its HER activity even after 1000 cycles. Furthermore, the stability of Ru/Fe3O4/MWCNTs was studied using the chronopotentiometric (CP) technique for 12 h and found negligible loss in the catalytic activity towards the HER. To explore the role of Ru and underneath MWCNTs in improving the catalytic performance of Fe3O4, density functional theory (DFT) calculations were carried out. DFT calculations indicate that the octahedral site of Ru/Fe3O4 favors the HER with a low overpotential. However, Ru/Fe3O4/MWCNTs are more efficient towards the HER, which could be due to the availability of both octahedral and tetrahedral catalytic sites. [ABSTRACT FROM AUTHOR]

Generation of molecular hydrogen by electrochemical water splitting is a promising approach, and its efficiency strictly depends on the electrocatalyst used. Therefore, it is an ongoing challenge to design materials having improved the electrocatalytic behaviour towards hydrogen evolution reaction. Here, using Co-MOF [Co4(BTC)3(BIm)6] as starting precursor, graphitic carbon encapsulated CoSe2 nanorods have been prepared through a single step selenization method. The carbon network in the CoSe2/C hybrid nanostructure forms channels, facilitating the accessibility of the electrolyte ions and maximizing the utilization of catalytic active centers. This makes the hybrid to show higher electrochemical accessible surface area, lower charge transfer resistance, and improved catalytic durability towards the electrocatalytic hydrogen evolution reaction with respect to the non-noble metal (graphite rod) counter electrode. Specifically, it needs only 253 mV of overpotential to reach the benchmarked current density (10 mA cm−2) with a lower Tafel slope. Further, the experimental findings have been supported by the theoretical analysis of the structure and electronic properties of CoSe2 and CoSe2/C hybrid by density functional theory (DFT) simulations. The interaction between CoSe2 and C is due to charge transfer from Co 3d orbital and Se 4p orbital of CoSe2 to the 2p orbital of carbon. Also, populated electronic states near Fermi level for C doped CoSe2 may infer towards increased conductivity of the material. Computed overpotentials for HER activities show a qualitative order of CoSe2/C < CoSe2, matching nicely with the experimental data. The synergic effect of increased conductivity, improved surface area, and superior electrocatalytic activity due to C doping is responsible for the superior HER catalytic performance. [ABSTRACT FROM AUTHOR]

The electrochemical nitrogen reduction reaction (NRR) is currently the most attractive method for ammonia production, in which the development of high efficiency and low-cost electrocatalysts is still a challenge. A lot of recent research has been focused on B single-atom catalysts. However, doping carbon materials with multiple hetero-elements has been rarely explored. Herein, we investigate the catalytic performance of B doped, N doped, and BN co-doped defective graphdiyne (B@GDY, N@GDY and BN@GDY) for nitrogen reduction by using density functional theory. Our results reveal that BN@GDY exhibits higher catalytic efficiency relative to that of single B doping, which is manifested by a significant decrease in overpotential (0.32 V vs. 0.61 V) via the enzymatic mechanism. The projected density of states and Bader charge analysis indicate that BN@GDY can promote the charge transfer from the catalytic substrate to adsorbed N2, in which the addition of N can convert B from sp2 to sp3 hybridization. Meanwhile, the competing hydrogen evolution reaction (HER) can be well inhibited during the NRR for both B/BN@GDY substrates, especially in BN@GDY, indicating the high selectivity of BN@GDY towards the NRR. Above all, this work puts forward a novel metal-free electrocatalyst for the NRR and may provide useful guidance for the design of new non-metal nitrogen reduction electrocatalysts. [ABSTRACT FROM AUTHOR]

To focus on renewable energy, we have been devoted to developping energy-efficient, robust and low cost water reduction catalysts (WRCs). Two hybrid inorganic–organic hexa/octa-CuII-sandwiched POM: [Cu(dap)2]2[{Cu8(dap)4(H2O)2} (SiW9O34)2]·7H2O (1) and [Cu(dap)2(H2O)]2[Cu(dap)2]2[{Cu6(dap)2}(SiW9O34)2]·8H2O (2) (dap = 1,2-diaminopropane, 1,4-H2NDC = 1,4-naphthalenedicarboxylic acid) were synthesized under hydrothermal conditions. The new copper complexes were applied as water reduction catalysts (WRCs) in the presence of [Ir(ppy)2(dtbbpy)][PF6] as a photosensitizer and triethanolamine (TEOA) as a sacrificial electron donor. Meanwhile, the number of nuclear substituted polyoxotungstates was the critical factor influencing photocatalysis. The experimental results matched well with the conclusions obtained via density functional theory (DFT). It is noteworthy that our research not only enriches the field of CuII-sandwiched POM chemistry but also provides an investigation of the relationship between photocatalytic activity and the nuclear number of Cu-substituted POMs. These results may guide us to synthesize different nuclear copper-substituted polyoxotungstates and develop their applications toward energy and environmental uses. [ABSTRACT FROM AUTHOR]

The photocatalytic hydrogen evolution inspired by the highly evolved, finely tuned molecular photo-synthetic systems in nature represents an important process in sustainable solar energy conversion for the near future. By incorporating a phosphine donor within a thiosemicarbazone moiety, a new proton reduction catalyst Ni−thioP, featuring Ni…H interactions was synthesized and structurally characterized. Single crystal structure analysis revealed that the C–S, C–N and N–N bond lengths were all within the normal range of the single and double bonds, suggesting the extensive electron delocalization over the ligand skeleton. The presence of Ni…H interactions relative to the amide group coupled with the easy proton migration pathway involving thioamide/thiolate exchange suggested that the thiosemicarbazone complexes could serve as promising candidates for proton reduction. Luminescence titrations exhibited that Ni−thioP served as efficient luminescent quenchers for the photosensitizer Fl, providing the possibilities for the excited state of Fl to activate these catalysts for proton reduction. The direct generation of hydrogen was achieved by carrying out the photolysis of a solution containing fluorescein as the photosensitizer, and triethylamine as the sacrificial and the redox catalysts. Ni−thioP exhibited high activity with a turnover number (TON) of 8000 moles of H2 per mole of the catalyst after 24 hours and an initial TOF larger than 500 moles of H2 per catalyst per hour. To further investigate the potential mechanism for proton reduction, calculations were also performed using density functional theory. [ABSTRACT FROM AUTHOR]

Electrochemical nitrogen reduction reactions (NRR) under ambient conditions are a promising and attractive way to ammonia (NH3) synthesis. It is significant to develop efficient and low-cost electrocatalysts for nitrogen reduction. Herein, an investigation of single B atom doped C5N2 as a metal-free electrocatalyst for NRR was carried out using density functional theory (DFT) calculations. The results show that the boron atom is preferentially doped into the interstitial site of C5N2. The formed B-interstitial (Bint)-doped C5N2 sufficiently activates the nitrogen (N2) molecule through the "acceptance–donation" process. In particular, N2 can be effectively reduced via an alternating mechanism with a low overpotential (0.38 V). Thus, by carefully controlling the doping sites, the B-doped C5N2 can be an ideal candidate for an efficient NRR, which may provide a new idea in the design of NH3 synthesis catalysts. [ABSTRACT FROM AUTHOR]

Searching for stable, efficient, and inexpensive metal-free electrocatalysts for the hydrogen evolution reaction (HER) is crucial for sustainable hydrogen generation. Herein, by means of density functional theory (DFT) computations, we proposed that P- or S-doping can effectively activate the basal plane of graphdiyne (GDY) for the HER. Our results revealed that these P- or S-doped GDY materials exhibit outstanding stability, enhanced electrical conductivity, and excellent magnetic properties. More interestingly, by carefully controlling the site and type of the P or S heteroatom, GDY can exhibit superior catalytic performance for the HER with the hydrogen adsorption free energy (ΔGH*) being near zero, which can be attributed to its moderate p-band centers near the Fermi level. Our work highlights a novel metal-free electrocatalyst for the HER, providing a promising strategy to rationally design highly efficient HER catalysts for sustainable H2 production. [ABSTRACT FROM AUTHOR]

Developing highly efficient electrocatalysts for multiple electrode reactions is of great importance for the large-scale applications of some energy conversion and storage devices. In this work, by means of spin-polarized density functional theory (DFT) computations, we have systematically explored the catalytic performance of several palladium (Pdn, n = 1–6, and 13) nanoclusters anchored on the experimentally available defective MoS2 monolayer with S monovacancy (Pdn/MoS2) for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Our results revealed that these studied Pdn/MoS2 materials have high stability due to the strong interaction of Pd clusters with the dangling Mo atoms and the S atoms around the vacancy with the binding energy per Pd atom ranging from −3.12 to −4.36 eV. Interestingly, the ORR/OER catalytic activity of these Pdn/MoS2 catalysts was greatly dependent on the sizes of the anchored Pd clusters: Pd6/MoS2 is predicted to exhibit the highest ORR catalytic activity due to its lowest overpotential of 0.59 V among all the studied catalysts, while Pd2/MoS2 is identified as the best OER catalyst due to its ultra-low overpotential of 0.32 V. Thus, our DFT results suggested that the ORR/OER catalytic performance could be effectively tuned by precisely controlling the sizes of the anchored Pd clusters on the MoS2 monolayer, which provides an important insight to further design novel and efficient ORR/OER catalysts. [ABSTRACT FROM AUTHOR]

The preparation of a highly active, cost-effective catalyst is the key to the commercial production of hydrogen through the electrochemical splitting of water, which is an ideal route to a clean energy conversion and storage system in the future. Unfortunately, the current catalysts for HER are rarely able to balance performance and cost. Herein, we successfully prepared an efficient catalyst (Ru/N–C) for HER by a facile method through a multi-step pyrolysis hard template. The electrochemical tests show that the HER activity of the synthesized Ru/N–C-6% catalyst with an onset potential of 0 mV and an overpotential of 34 mV at 10 mA cm−2 was comparable to that of Pt/C in 1 M KOH. Moreover, after 10 000 cycles, the potential change at 10 mA cm−2 is almost negligible. The origin of this high activity was analyzed via density functional theory (DFT), and the mechanism is further understood. Therefore, this work provides a promising substitute for Pt-based catalysts. [ABSTRACT FROM AUTHOR]

Introducing heteroatoms into two-dimensional nanosheets was revealed to be a quite promising strategy to tune their electronic and magnetic properties as well as chemical reactivity, thus greatly widening their application fields. Herein, by means of density functional theory (DFT) computations, we have systematically investigated the electronic and magnetic properties as well as chemical reactivity of MoS2 nanosheets doped with several common nonmetal dopants (B, C, N, O, and P). Our results revealed that these nonmetal atoms can be strongly captured by the S vacancy of the MoS2 nanosheet, ensuring their high stability. Compared with the pristine MoS2 nanosheet, these doped MoS2 systems exhibit decreased band gaps due to the introduction of impurity levels. In particular, the adsorption of gas molecules on the MoS2 monolayer can be enhanced to different degrees after nonmetal doping, suggesting great potential for developing gas sensors or catalysts. Thus, by carefully choosing the nonmetal atoms, the inert basal plane of a MoS2 nanosheet can be effectively activated for various applications. [ABSTRACT FROM AUTHOR]