Desorption Barrier Research Articles

Dual Modulation of Hydroxyl Action on Ruthenium Surface by Single‐Atom Supports for Alkaline H2 Evolution

AbstractRuthenium (Ru)‐based catalysts are known to accelerate the slow kinetics of the alkaline hydrogen evolution reaction (HER). However, enhancing the transfer kinetics of adsorbed hydroxyl (OHad) remains challenging. Herein, a dual‐regulation strategy is presented to alleviate OH blockage on the catalyst surface, using a cluster‐level Ru electrocatalyst supported by single‐atom CoN4 generated in situ on carbon nanotubes (CNTs). Experimental and theoretical studies demonstrate that introducing oxophilic single‐atom CoN4 can mitigate the strong interaction between Ru and OHad by directly competing for OHad on the Ru surface, thereby preventing Ru site poisoning. Meanwhile, single‐atom CoN4 effectively modifies the electronic structure of Ru atomic clusters (ACs), indirectly optimizing the energy barriers for OH desorption at the Ru interface and promoting OHad release. The electronic interaction between Ru ACs and CoN4 also inhibits Ru atom migration, significantly enhancing catalytic stability. The resulting catalyst shows excellent HER activity at 10 mA cm−2 with a low overpotential of 15 mV in alkaline solution and remains stable at 200 mA cm−2 for over 1000 h. An alkaline anion‐exchange membrane water electrolyzer (AEMWE) using this catalyst can exhibit an ultralow potential (1.785 V at 1 A·cm−2) and high stability at 500 mA·cm−2.

Boosting the Quantum Efficiency of Ionic Carbon Nitrides in Photocatalytic H2O2 Evolution via Controllable n → π* Electronic Transition Activation.

Hydrogen peroxide (H2O2) is a crucial chemical used in numerous industrial applications, yet its manufacturing relies on the energy-demanding anthraquinone process. Solar-driven synthesis of H2O2 is gaining traction as a promising research area, providing a sustainable method for its production. Herein, a controllable activation of n → π* electronic transition is presented to boost the photocatalytic H2O2 evolution in ionic carbon nitrides. This enhancement is achieved through the simultaneous introduction of structural distortions and defect sites (─C ≡ N groups and N vacancies) into the KPHI framework. The optimal catalyst (2%Ox-KPHI) reached an apparent quantum yield of 41% at 410nm without the need for any cocatalysts, outperforming most previously reported carbon nitride-based photocatalysts. Extensive experimental characterizations and theoretical calculations confirm that a corrugated configuration and the presence of defects significantly broaden the light absorption profile, improve carrier separation and migration, promote O2 adsorption, and lower the energy barriers for H2O2 desorption. Transient absorption spectroscopy indicates that the enhanced photocatalytic performance of 2%Ox-KPHI is largely attributed to the preferential migration of electrons at defect sites over extended timescales, following the diffusion of geminate carriers across the PHI sheets.

Modulating stacking mode and molecular polarization in CTF/molecule heterojunction for meliorating photocatalytic CO2 conversion with nearly 100% CO selectivity

Herein, two conjugated molecules, i.e., D-π-A TAPT and non-D-A TAPB, are finely designed to incorporate with covalent triazine framework (CTF) in A-A and A-B stacking mode via π-π interaction, respectively. The transient photocurrent response of the generated AA-CTF/TAPT Z-Scheme heterostructure is 1.14 × 10-7 A, significantly higher than that of the other two metal-free heterostructures (AA-CTF/TAPB and AB-CTF/TAPT). The promoted photocarrier transportation is attributed to strong polarization (dipole moment = 2.634 D) imposed by the D-π-A effect in TAPT that motivates the interfacial charge separation, and the coexisting charge transfer channel built by the ordered A-A stacking mode in AA-CTF that expedites the charge delivery. The photocatalytic CO2 conversion conducted by AA-CTF/TAPT gives the optimal CO conversion rate as 7.47 μmol·g−1·h−1, and with nearly 100 % product selectivity obtained, which is attributable to the lower energy barrier of CO desorption barrier (−1.07 eV) rather than that of CHO* formation (1.52 eV) for generating CH4.

P-tuned FeN2 binuclear sites for boosted CO2 electro-reduction

The recycling of CO2 through electrochemical processes offers a promising solution for alleviating the greenhouse effect; however, the activation of CO2 and desorption of *CO in electrocatalytic CO2 reduction (ECR) frequently encounter high energy barriers and competitive hydrogen evolution reactions (HERs), which are urgent problems that need to be addressed. In this study, a catalyst (P100–Fe–N/C) with homogeneous P–tuned FeN2 binuclear sites (N2PFe-FePN2) was successfully synthesised, demonstrating satisfactory performance in the ECR to CO. P100–Fe–N/C attains a peak FECO of 98.01% and a normalized TOF of 664.7 h-1 at −0.7 VRHE, surpassing the performance of the Fe binuclear catalyst without P and single-atoms catalysts. In the MEA cell, a FECO exceeding 90% can still be achieved. Density functional theory analysis indicates that the asymmetric coordination configuration induced by the incorporation of P facilitates a reduction in the system’s energy. The modulation of P results in the d-band centre of the catalyst being positioned closer to the Fermi level, which facilitates the interaction of the catalyst with CO2, allowing more electrons to be injected into the CO2 molecule at the Fe binuclear sites and inhibiting the HER. The P–tuned FeN2 binuclear sites effectively lower the *CO desorption barrier.

Identifying Highly Active and Selective Cobalt X-Ides for Electrocatalytic Hydrogenation of Quinoline.

Earth-abundant Co X-ides are emerging as promising catalysts for the electrocatalytic hydrogenation of quinoline (ECHQ), yet challenging due to the limited fundamental understanding of ECHQ mechanism on Co X-ides. This work identifies the catalytic performance differences of Co X-ides in ECHQ and provides significant insights into the catalytic mechanism of ECHQ. Among selected Co X-ides, the Co3O4 presents the best ECHQ performance with a high conversion of 98.2% and 100% selectivity at ambient conditions. The Co3O4 sites present a higher proportion of 2-coordinated hydrogen-bonded water at the interface than other Co X-ides at a low negative potential, which enhances the kinetics of subsequent water dissociation to produce H*. An ideal 1,4/2,3-H* addition pathway on Co3O4 surface with a spontaneous desorption of 1,2,3,4-tetrahydroquinoline is demonstrated through operando tracing and theoretical calculations. In comparison, the Co9S8 sites display the lowest ECHQ performance due to the high thermodynamic barrier in the H* formation step, which suppresses subsequent hydrogenation; while the ECHQ on Co(OH)F and CoP sites undergo the 1,2,3,4- and 4,3/1,2-H* addition pathway respectively with the high desorption barriers and thus low conversion of quinoline. Moreover, the Co3O4 presents a wide substrate scope and allows excellent conversion of other quinoline derivatives and N-heterocyclic substrates.

A highly efficient semi-finishing approach for polycrystalline diamond film via plasma-based anisotropic etching

Plasma anisotropic etching polishing (plasma-AEP), a non-contact polishing method, is proposed to achieve highly efficient planarization of polycrystalline diamond (PCD) films. Inductively coupled plasma, with a high concentration of reactive radicals, serves as the source of plasma-AEP. In-situ observation confirms that the planarization effect of plasma-AEP is realized through the preferential removal of the top areas of the pyramid-shaped protrusions, despite the entire surface being uniformly irradiated by the plasma. The material removal rate in plasma-AEP for PCD achieves 127 μm/min. Plasma-AEP is proven effective for PCD films with thicknesses of 0.5, 1, and 2 mm, demonstrating a generic semi-finishing approach for PCD regardless of thickness. Atomic-scale nudged elastic band calculations revealed that the energy barriers for CO and CO2 desorption from 1- and 2-coordinated C atoms are significantly lower than those for 3- and 4-coordinated ones. ReaxFF molecular dynamics simulations showed that at the top areas of the pyramid-shaped protrusions, 1- and 2-coordinated C atoms with a higher etching priority remained dominant during plasma-AEP, leading to the preferential removal of C atoms forming these protrusions. Furthermore, contact polishing was added to complete the finishing of the PCD film, followed by plasma-AEP, resulting in a nanoscale smooth surface with a roughness of 3.4 nm. Transmission electron microscopy confirmed that the crystal structures on the surface and subsurface of the PCD film were well ordered. Overall, this paper displays that plasma-AEP is a promising approach for highly efficient semi-finishing of PCD films.

Molecular Engineering of Methylated Sulfone‐Based Covalent Organic Frameworks for Back‐Reaction Inhibited Photocatalytic Overall Water Splitting

AbstractSolar‐to‐hydrogen (H2) and oxygen (O2) conversion via photocatalytic overall water splitting (OWS) holds great promise for a sustainable fuel economy, but has been challenged by the backward O2 reduction reaction (ORR) with favored proton‐coupled electron transfer (PCET) dynamics. Here, we report that molecular engineering by methylation inhibits the backward ORR of molecular photocatalysts and enables efficient OWS process. As demonstrated by a benchmark sulfone‐based covalent organic framework (COF) photocatalyst, the precise methylation of its O2 adsorption sites effectively blocks electron transfer and increases the barrier for hydrogen intermediate desorption that cooperatively obstructs the PCET process of ORR. Methylation also repels electrons to the neighboring photocatalytic sulfone group that promotes the forward H2 evolution. The resultant DS‐COF achieves an impressive inhibition of about 70 % of the backward reaction and a three‐fold enhancement of the OWS performance with a H2 evolution rate of 124.7 μmol h−1 g−1, ranking among the highest reported for organic‐based photocatalysts. This work provides insights for engineering photocatalysts at the molecular level for efficient solar‐to‐fuel conversion.

Molecular Engineering of Methylated Sulfone-Based Covalent Organic Frameworks for Back-Reaction Inhibited Photocatalytic Overall Water Splitting.

Solar-to-hydrogen (H2) and oxygen (O2) conversion via photocatalytic overall water splitting (OWS) holds great promise for a sustainable fuel economy, but has been challenged by the backward O2 reduction reaction (ORR) with favored proton-coupled electron transfer (PCET) dynamics. Here, we report that molecular engineering by methylation inhibits the backward ORR of molecular photocatalysts and enables efficient OWS process. As demonstrated by a benchmark sulfone-based covalent organic framework (COF) photocatalyst, the precise methylation of its O2 adsorption sites effectively blocks electron transfer and increases the barrier for hydrogen intermediate desorption that cooperatively obstructs the PCET process of ORR. Methylation also repels electrons to the neighboring photocatalytic sulfone group that promotes the forward H2 evolution. The resultant DS-COF achieves an impressive inhibition of about 70 % of the backward reaction and a three-fold enhancement of the OWS performance with a H2 evolution rate of 124.7 μmol h-1 g-1, ranking among the highest reported for organic-based photocatalysts. This work provides insights for engineering photocatalysts at the molecular level for efficient solar-to-fuel conversion.

Constructing the synergistic active sites of nickel bicarbonate supported Pt hierarchical nanostructure for efficient hydrogen evolution reaction

Constructing synergistic active sites and optimizing the cooperative adsorption energies for hydrogen and hydroxyl based intermediates are two essential strategies to improve the sluggish kinetics of hydrogen evolution reaction (HER) in alkaline medium. However, it is still in its infancy to simultaneously achieve these goals, especially for designing a well-defined carrier with multiple hydroxyl adsorption sites. Herein, the Ni(HCO3)2 nanoplates (NHC) with horizontal interfaces sites of Ni-terminated NiO, NiOOH, NiCOO, and Ni(OH)2 were employed as the hydroxyl adsorption active sites, which could anchor Pt particles with hydrogen adsorption active sites, constructing the synergistic active sites (NHC-Pt) for HER catalysis. Evidenced by X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS), the NHC could affect the chemical state and electronic structure of Pt particles by forming bond of Pt-O which could reduce the reaction energy barriers, facilitate the adsorption of hydrogen and establishment of H–H bond. Furthermore, density functional theory (DFT) theoretical calculation revealed that the related process of hydroxide was the rate-determining step. It is demonstrated the hydroxyl group presents the lowest energy barrier for desorption in the process of HER when the gradual desorption process could be described as a migration from Ni(HCO3)2·OH directly or via other Ni-based systems formed after partial decomposition of nickel hydrocarbonate to Ni(OH)2···OH with following desorption. As a result, the NHC-Pt hierarchical nanostructure demonstrated superior activity towards HER in a pH-universal solution. This enhancement can be attributed to the optimized electronic structure of Pt, the migration of hydroxyl group on NHC substrates, and the synergistic effects between the NHC carrier and Pt particles.

Impact of Vertex Functionalization on Flexibility of Porous Organic Cages.

Efficient carbon capture requires engineered porous systems that selectively capture CO2 and have low energy regeneration pathways. Porous liquids (PLs), solvent-based systems containing permanent porosity through the incorporation of a porous host, increase the CO2 adsorption capacity. A proposed mechanism of PL regeneration is the application of isostatic pressure in which the dissolved nanoporous host is compressed to alter the stability of gases in the internal pore. This regeneration mechanism relies on the flexibility of the porous host, which can be evaluated through molecular simulations. Here, the flexibility of porous organic cages (POCs) as representative porous hosts was evaluated, during which pore windows decreased by 10-40% at 6 GPa. POCs with sterically smaller functional groups, such as the 1,2-ethane in the CC1 POC resulted in greater imine cage flexibility relative to those with sterically larger functional groups, such as the cyclohexane in the CC3 POC that protected the imine cage from the application of pressure. Structural changes in the POC also caused CO2 adsorption to be thermodynamically unfavorable beginning at ∼2.2 GPa in the CC1 POC, ∼1.1 GPa in the CC3 POC, and ∼1.0 GPa in the CC13 POC, indicating that the CO2 would be expelled from the POC at or above these pressures. Energy barriers for CO2 desorption from inside the POC varied based on the geometry of the pore window and all the POCs had at least one pore window with a sufficiently low energy barrier to allow for CO2 desorption under ambient temperatures. The results identified that flexibility of the CC1, CC3, or CC13 POCs under compression can result in the expulsion of captured gas molecules.

Homogeneous In‐Plane Lattice Strain Enabling d‐Band Center Modulation and Efficient d–π Interaction for an Ag2Mo2O7 Cathode Catalyst With Ultralong Cycle Life in Li‐O2 Batteries

AbstractAlthough lithium–oxygen batteries (LOBs) hold great promise as future energy storage systems, they are impeded by insulated discharge product Li2O2 and sluggish oxygen reduction reaction/oxygen evolution revolution (ORR/OER) kinetics. The application of a highly efficient cathode catalyst determines the LOBs performance. The d‐band modulation and catalytic kinetics promotion are important concept guidelines for the performance enhancement of cathode catalysts. In this work, the homogeneous in‐plane distortion‐derived synergistic catalytic capability of an Ag2Mo2O7 catalyst with modulated d‐band centers and promoted ORR/OER kinetics is demontrated. The uniform elongation of Ag─O bonds and compression of Mo─O bonds in (020) plane leads to d‐band splitting and d‐band center optimization and delivers improved adsorption behavior for high ORR/OER capability. Furthermore, the spatial and energy overlap of Ag dxz and O2 anti‐bonding π* orbitals facilitate electron injection during ORR process and reduce the energy barrier for charge transfer and O2 desorption during OER process, accelerating the ORR/OER kinetics. As a result, the (020) plane‐exposed Ag2Mo2O7 cathode exhibits ultralong cycle stability of 817 cycles at 500 mA g−1 and large specific discharge/charge capacities of 15898/15180 mAh g−1. This work provides facile concept guidance for optimizing catalytic capability through controlled lattice distortion in cathode catalysts for LOBs.

Activation Energy of Ion Desorption at Ionic Liquid/Pt Electrode Interfaces: A Sum-Frequency Generation Vibrational Spectroscopic Study.

Electrolyte/electrode interfaces of room-temperature ionic liquids (RTILs) exhibit hysteretic responses to different applied potentials owing to the differences in the ion adsorption/desorption processes; the ion desorption requires excess potential, which reflects the activation energy of ion desorption. Thus far, the contributions of the ion adsorption energy and the activation barrier for ion desorption toward the ion-dependent excess potential have not been quantified. Herein, we report on our infrared-visible sum-frequency generation vibrational spectroscopy study of the hysteretic responses of the anion adsorption/desorption at Pt electrode interfaces using neat, binary, and diluted RTILs composed of 1-butyl-3-methylimidazolium cations ([C4mim]+) and bis(trifluoromethanesulfonyl)amide ([TFSA]-) and trifluoromethanesulfonate ([OTf]-) anions. Experimental results are compared to the theoretical calculations for the electric double layer model. The hysteretic response of the RTIL/Pt interface derives predominantly from the activation energy of anion desorption, which causes the negative excess potential required for anion desorption. A comparison of the anion adsorption/desorption behaviors of neat RTILs with those of binary and diluted RTILs reveals that the large activation energy of anion desorption at the neat RTIL/Pt interface originates largely from the activation barrier for restructuring ionic layering in the diffuse layer.

Single-atom Al precisely modulate the strain of Pt3Co intermetallic for superior oxygen catalytic performance

Precisely controlling the strain of Pt-based intermetallic to ensure high performance and stability is a massive task for sustainable proton-exchange-membrane-fuel-cells. Herein, the Al single-atom was trapped into the L12-Pt3Co intermetallic core to precisely tailor the strain state on the Pt-skin for fast oxygen reduction reaction kinetics. Theoretical calculations firstly predicted that only tailored tension can accelerate the protonation of O2 on L12-Pt3Co@Pt without creating an additional energy barrier for subsequent oxygen-containing intermediates desorption. Experimentally, Al single-atom confined in the L12-Pt3Co lattice by substituting partial Co occupancy, imposing tailored ∼ 0.2 % tension on Pt-skin compared to the L12-Pt3Co. L12-Al-Pt3Co@Pt/C exhibits enhanced mass activity which is ten-time improvement over commercial Pt/C. More significantly, XAS and DFT results reveal that the Al single-atom can strengthen the Pt-Co bonding, enhancing the stability of L12-Al-Pt3Co@Pt/C in oxygen reduction. This work provides an avenue to design the strain by single-atom for sustainable energy conversion technologies.

Bioinspired axial S-coordinated single-atom cobalt catalyst to efficient activate peroxymonosulfate for selective high-valent Co-Oxo species generation

The efficient activation and selective high-valent metal-oxo (HVMO) species generation remain challenging for peroxymonosulfate (PMS)-based advanced oxidation processes (PMS-AOPs) in water purification. The underlying mechanism of the activation pathway is ambiguous, leading to a massive dilemma in the control and regulation of HVMO species generation. Herein, bioinspired by the bio-oxidase structure of cytochrome P450, the axial coordination strategy was adopted to tailor a single-atom cobalt catalyst (CoN4S-CB) with an axial S coordination. CoN4S-CB high-selectively generated high-valent Co-Oxo species (Co(IV)=O) via PMS activation. Co(IV)=O demonstrated an ingenious oxygen atom transfer (OAT) reaction to achieve the efficient degradation of sulfamethoxazole (SMX), and this allowed robust operation in various complex environments. The axial S coordination modulated the 3d orbital electron distribution of the Co atom. Density functional theory (DFT) calculation revealed that the axial S coordination decreased the energy barrier for PMS desorption and lowered the free energy change (ΔG) for Co(IV)=O generation. CoN4S-PMS* had a narrow d-band close to the Fermi level, which enhanced charge transfer to accelerate the cleavage of O-O and O-H bonds in PMS. This work provides a broader perspective on the activator design with natural enzyme structure-like active sites to efficient activate PMS for selective HVMO species generation.

Revealing the mechanism of structure-electron effect in mechanochemistry-driven CuS-coupled layered g-C3N4 Schottky-junction for enhanced demercuration

The development of cost-effective heterojunctions with heightened affinity for mercury (Hg0) presents a promising approach for mercury abatement from stationary source emissions. In this study, one novel hierarchical porous Schottky heterojunction composed of CuS-coupled layered g-C3N4 (CuS-CN) was synthesised via a mechanochemistry-driven acetate route. The prepared CuS-CN heterojunction exhibited a considerable Hg0 accommodation capacity of 33.04 mg/g at 70 °C and a breakthrough threshold of 60%, which was 40% higher than that of CuS-CN(mix) prepared by simply mixing CuS and CN without forming a heterojunction interface. Additionally, the CuS-CN heterojunction demonstrated satisfactory applicability against various simulated stationary source exhausts. Furthermore, the reason for the unparalleled and enhanced demercuration performance of the CuS-CN heterojunction was systematically deduced via experimental studies and first-principles calculations. Under-coordinated disulfides (S22−) on the CuS-CN surface served as the primary active centre for the oxidation of Hg0 to Hg2+ and simultaneous bonding site for Hg2+ to form HgS. The well-developed electron transport network and narrow bandgap energy of the CuS-CN heterojunction enhanced charge separation and transfer from Hg0 and CN to CuS, accelerating Hg0 oxidation reaction, which resulted in an enhanced adsorption energy of −344.52 kJ/mol. Additionally, the CuS-CN heterojunction exhibited stronger Hg0 oxidation and weaker HgS adsorption properties, attributed to the lower bond strength of HgS on the CuS-CN surface and lower energy barrier for HgS desorption. Thus, this study highlighted the effectiveness of the CuS-CN heterojunction in Hg0 abatement and presented a promising strategy for the mechanochemical synthesis of mercury removal agents for large-scale industrial applications.

Screening Spinel Oxide Supports for RuO2 to Boost Bifunctional Electrocatalysts for Advanced Zn–Air Batteries

AbstractThe compositing strategy offers great potential in designing bifunctional oxygen electrocatalysts for Zn–air batteries. Recent reports reveal that the couple of RuO2, serving as a benchmark oxygen evolution reaction (OER) catalyst, with other oxygen reduction reaction (ORR) catalysts is a wise choice to build highly efficient bifunctional electrocatalysts. However, the design criteria for ORR and OER activities of RuO2‐based composite catalysts are still unclear. Herein, a series of transition metal (Fe, Co, Mn, and Ni)‐doped spinel oxides are designed to support RuO2 nanorods for exploring the reaction mechanism. Through advanced technology, it is considered that increasing the content and binding energy of Co3+ and enhancing the oxidation state of Ru4+ is an efficient strategy to promote ORR and OER activities for RuO2/Co‐based spinel oxide composite catalysts. It is found that coupling Mn‐doping Co3O4 (CMO) supports with RuO2 can induce the highest catalytic activities in ORR/OER and excellent performance in rechargeable Zn–air batteries. Operando electrochemical impedance spectroscopy and theoretical calculation further prove the synergistic effect between RuO2 and CMO supports originated from the oxygen overflow to overcome the large barrier for oxygen desorption on RuO2 during OER and oxygen adsorption on CMO supports during ORR.

Computational demystification of iron carbonyls formation under syngas environment

Iron pentacarbonyl (IPC) gas forms upon the reaction of carbon monoxide with Fe containing metallic surfaces under gas reforming conditions. IPC formation can sometimes reach alarming levels that cause metal loss, pipeline thinning corrosion, catalyst poisoning, and contamination of sensitive industrial equipment. In this work, we demystify using multiscale computational modeling the mechanism of Iron pentacarbonyl formation: Density functional theory (DFT) is used to explore various catalytic reactions that involve a Fe adatom reacting with adsorbed carbon monoxide. Our calculated carbonyls desorption barriers on a perfect and clean Fe surface are too high to allow the carbonyls to form then desorb at temperatures <500 K at the rates reported experimentally. Most importantly, our calculations indicate that a high CO surface coverage, in addition to the presence of Fe adatoms, favors carbonyl formation and its desorption towards the flowing gas medium. Using insights extracted from ab initio molecular dynamics simulations, we propose that the most plausible IPC formation mechanism consists of: (1) on surface reactions of adsorbed CO molecules with an Fe adatom to form iron tricarbonyl (Fe(CO)3*) molecules; (2) an adsorbate assisted movement of iron tricarbonyl on top of the CO adlayer; and (3) the interaction of iron tricarbonyl with CO molecules from the gaseous medium eventually leading to iron adatom removal as Fe(CO)5 gas.

Substantial Impact of Built-in Electric Field and Electrode Potential on the Alkaline Hydrogen Evolution Reaction of Ru-CoP Urchin Arrays.

Although great efforts on the delicate construction of a built-in electric field (BIEF) to modify the electronic properties of active sites have been conducted, the substantial impact of BIEF coupled with electrode potential on the electrochemical reactions has not been clearly investigated. Herein, we designed an alkaline hydrogen evolution reaction (HER) catalyst composed of heterogeneous Ru-CoP urchin arrays on carbon cloth (Ru-CoP/CC) with a strong BIEF with the guidance of density functional theory (DFT) calculations. Impressively, despite its unsatisfactory activity at 10 mA cm-2 (overpotential of 44 mV), Ru-CoP/CC exhibited better activity (357 mV) than the benchmark Pt/C catalyst (505 mV) at 1 A cm-2 . Experimental and theoretical studies revealed that strong hydrogen adsorption on the interfacial Ru atoms created a high energy barrier for hydrogen desorption and spillover, resulting in unsatisfactory activity at low current densities. However, as the electrode potential became more negative (i.e., the current density increased), the barrier for hydrogen spillover from the interfacial Ru to the Co site, which had near-zero hydrogen adsorption energy, significantly decreased, thus greatly accelerating the whole alkaline HER process. This explains why the activity of Ru-CoP is relatively susceptible to the electrode potential compared to Pt/C.

Hybrid RPA:DFT Approach for Adsorption on Transition Metal Surfaces: Methane and Ethane on Platinum (111).

The hybrid QM:QM approach is extended to adsorption on transition metal surfaces. The random phase approximation (RPA) as the high-level method is applied to cluster models and, using the subtractive scheme, embedded in periodic models which are treated with density functional theory (DFT) that is the low-level method. The PBE functional, both without dispersion and augmented with the many-body dispersion (MBD), is employed. Adsorption of methane and ethane on the Pt(111) surface is studied. For methane in a 2 × 2 surface cell, the hybrid RPA:PBE and RPA:PBE+MBD results, -14.3 and -16.0 kJ mol-1, respectively, are in close agreement with the periodic RPA value of -13.8 kJ mol-1 at significantly reduced computational cost (factor of ∼50). For methane and ethane, the RPA:PBE results (-14.3 and -17.8 kJ mol-1, respectively) indicate underbinding relative to energies derived from experimental desorption barriers for relevant loadings (-15.6 ± 1.6 and -27.2 ± 2.9 kJ mol-1, respectively), whereas the hybrid RPA:PBE+MBD results (-16.0 and -24.9 kJ mol-1, respectively) agree with the experiment well within experimental uncertainty limits (deviation of -0.4 ± 1.5 and +2.3 ± 2.9 kJ mol-1, respectively). Finding a cluster that adequately and robustly represents the adsorbate at the bulk surface is important for the success of the RPA-based QM:QM scheme for metals.

Electron-enriched single-Pd-sites on g-C3N4 nanosheets achieved by in-situ anchoring twinned Pd nanoparticles for efficient CO2 photoreduction

Modulating electronic structures of single-atom metal cocatalysts is vital for highly active photoreduction of CO2, and it's especially challenging to develop a facile method to modify the dispersion of atomical photocatalytic sites. We herein report an ion-loading pyrolysis route to in-situ anchor Pd single atoms as well as twinned Pd nanoparticles on ultra-thin graphitic carbon nitride nanosheets (PdTP/PdSA-CN) for high-efficiency photoreduction of CO2. The anchored Pd twinned nanoparticles donate electrons to adjacent single Pd–N4 sites through the carbon nitride networks, and the optimized PdTP/PdSA-CN photocatalyst exhibits a CO evolution rate up to 46.5 ​μmol ​g−1 ​h−1 with nearly 100% selectivity. As revealed by spectroscopic and theoretical analyses, the superior photocatalytic activity is attributed to the lowered desorption barrier of carbonyl species at electron-enriched Pd single atoms, together with the improved efficiencies of light-harvesting and charge separation/transport. This work has demonstrated the engineering of the electron density of single active sites with twinned metal nanoparticles assisted by strong electronic interaction with the support of the atomic metal, and unveiled the underlying mechanism for expedited photocatalytic efficiency.