N,S coordination in Ni single-atom catalyst promoting CO2RR towards HCOOH.

Carbon-based single atom catalysts (SACs) are attracting extensive attention in the CO2 reduction reaction (CO2RR) due to their maximal atomic utilization, easily regulated active center and high catalytic activity, in which the coordination environment plays a crucial role in the intrinsic catalytic activity. Taking NiN4 as an example, this study reveals that the introduction of different numbers of S atoms into N coordination (Ni-NxS4-x (x = 1-4)) results in outstanding structural stability and catalytic activity. Owing to the additional orbitals around -1.60 eV and abundant Ni dxz, dyz, dx2, and dz2 orbital occupation after S substitution, N,S coordination can effectively facilitate the protonation of adsorbed intermediates and thus accelerate the overall CO2RR. The CO2RR mechanisms for CO and HCOOH generation via two-electron pathways are systematically elucidated on NiN4, NiN3S1 and NiN2S2. NiN2S2 yields HCOOH as the most favorable product with a limiting potential of -0.24 V, surpassing NiN4 (-1.14 V) and NiN3S1 (-0.50 V), which indicates that the different S-atom substitution of NiN4 has considerable influence on the CO2RR performance. This work highlights NiN2S2 as a high-performance CO2RR catalyst to produce HCOOH, and demonstrates that N,S coordination is an effective strategy to regulate the performance of atomically dispersed electrocatalysts.

Two-dimensional MBene: a comparable catalyst to MXene for effective CO2RR towards C1 products.

Electrochemical CO2 reduction reaction (CO2RR) to high-value-added products is one of the most promising strategies for mitigating the greenhouse effect and energy shortage. Two-dimensional (2D) MXene materials are regarded as promising catalysts for electrocatalysis, and the boron-analogs of MXenes, 2D transition metal borides (MBenes), may exhibit superior CO2RR performance owing to their unique electronic properties. Herein, a novel 2D transition metal boride, MoB, is theoretically evaluated as a potential catalyst for the CO2RR by comparing it with traditional Mo2C. MoB shows metallic nature and exhibits excellent electrical conductivity. MoB can effectively activate CO2 with a larger interaction energy of -3.64 eV than that of Mo2C. Both density of states and charge difference density reveal a significant charge transfer from MoB to CO2. MoB shows higher catalytic selectivity due to its inhibited hydrogen evolution reaction and low reaction energy for the CO2RR. At potentials more negative than -0.62 V, the CO2RR on MoB becomes a high-throughput reaction process towards CH4. This work discovered that MoB exhibited comparable CO2RR performance to Mo2C and forecasted MBenes as promising catalysts for electrocatalysis.

In-situ construction of iron-modified nickel nanoparticles assisted by hexamethylenetetramine with the internal and external collaboration for highly selective electrocatalytic carbon dioxide reduction.

Carbon dioxide (CO2) electroreduction provides a sustainable route for realizing carbon neutrality and energy supply. Up to now, challenges remain in employing abundant and inexpensive nickel materials as candidates for CO2 reduction due to their low activity and favorable hydrogen evolution. Here, the representative iron-modified nickel nanoparticles embedded in nitrogen-doped carbon (Ni1-Fe0.125-NC) with the porous botryoid morphology were successfully developed. Hexamethylenetetramine is used as nitrogen-doped carbon source. The collaboration of internal lattice expansion with electron effect and external confinement effect with size effect endows the significant enhancement in electrocatalytic CO2 reduction. The optimized Ni1-Fe0.125-NC exhibits broad potential ranges for continuous carbon monoxide (CO) production. A superb CO Faradaic efficiency (FECO) of 85.0 % realized at -1.1 V maintains a longtime durability over 35 h, which exceeds many state-of-the-art metal catalysts. Theoretical calculations further confirm that electron redistribution promotes the desorption of CO in the process for favorable CO production. This work opens a new avenue to design efficient nickel-based materials by considering the intrinsic structure and external confinement for CO2 reduction.

Storage and dynamics of soil organic carbon in allochthonous-dominated and nitrogen-limited natural and planted mangrove forests in southern Thailand.

Mangrove forests can help to mitigate climate change by storing a significant amount of carbon (C) in soils. Planted mangrove forests have been established to combat anthropogenic threats posed by climate change. However, the efficiency of planted forests in terms of soil organic carbon (SOC) storage and dynamics relative to that of natural forests is unclear. We assessed SOC and nutrient storage, SOC sources and drivers in a natural and a planted forest in southern Thailand. Although the planted forest stored more C and nutrients than the natural forest, the early-stage planted forest was not a strong sink relative to mudflat. Both forests were predominated by allochthonous organic C and nitrogen limited, with total nitrogen being a major driver of SOC in both cases. SOC showed a significant decline along land-to-sea and depth gradients as a result of soil texture, nutrient availability, and pH in the natural forest.

Precise electronic structure modulation on MXene-based single atom catalysts for high-performance electrocatalytic CO2 reduction reaction: A first-principle study.

Electrocatalytic CO2 reduction reaction (CO2RR) to CO is a logical approach to achieve a carbon-neutral cycle. In this work, a series of Ti2CO2 and O vacancy containing Ti2CO2 MXene-based transition metal (TM) single atom catalysts (SACs), including TM-Ti2CO2 and TM-Ov-Ti2CO2, are explored for high-performance CO2RR. Sc/Ti/V/Cr-Ti2CO2 and Ni-Ov-Ti2CO2 are screened out with limiting potential (UL) more positive than -0.50 V. Ni-Ov-Ti2CO2 is a candidate catalyst for CO2RR to CO, considering its activity with UL of -0.27 eV, and the selectivity relevant to hydrogen evolution reaction and HCOOH production. Meanwhile, a novel activity descriptor of TM-Ti-O group valence state is proposed according to that TMs work in synergy with coordinated Ti and O atoms and a level of around 0.64 e- benefits to CO2RR. This work highlights oxygen vacancy containing Ti2CO2-based Ni SAC as a promising catalyst for CO2RR, and provides a feasible electronic structure design principle for guiding the design of MXene-based SACs for CO2RR.

Constructing N,S and N,P Co-Coordination in Fe Single-Atom Catalyst for High-Performance Oxygen Redox Reaction.

Single-atom catalysts (SACs) are promising electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER), in which the coordination environment plays a crucial role in activating the intrinsic activity of the central metal. Taking the FeN4 SAC as a probe, this work investigates the effect of introducing S or P atoms into N coordination (FeSx N4-x and FePx N4-x (x=1-4)) on the electronic structure optimization of Fe center and its catalytic performance. Attributing to the optimal Fe 3d orbitals, FePN3 can effectively activate O2 and promote ORR with a low overpotential of 0.29 V, surpassing FeN4 and most reported catalysts. FeSN3 is beneficial to H2 O activation and OER, proceeding with an overpotential of 0.68 V, which is superior to FeN4 . Both FePN3 and FeSN3 exhibit outstanding thermodynamic and electrochemical stability with negative formation energies and positive dissolution potentials. Hence, the N,P and N,S co-coordination might provide better catalytic environment than regular N coordination for SACs in ORR and OER. This work demonstrates FePN3 /FeSN3 as high-performance ORR/OER catalysts and highlights N,P and N,S co-coordination regulation as an effective approach to fine tune high atomically dispersed electrocatalysts.