Exploring earth-abundant electrocatalysts with Pt-like performance toward alkaline hydrogen evolution reaction (HER) is extremely desirable for the hydrogen economy but remains challenging. Herein, density functional theory (DFT) predictions reveal that the electronic structure and localized charge density at the heterointerface of NiP2–FeP2 can be significantly modulated upon coupling with metallic Cu, resulting in optimized proton adsorption energy and reduced barrier for water dissociation, synergistically boosting alkaline HER. Motivated by theoretical predictions, we developed a facile strategy to fabricate interface-rich NiP2–FeP2 coupled with Cu nanowires (CuNW) grown on Cu foam (NiP2–FeP2/CuNW/Cuf). Benefiting from the superior intrinsic activity, conductivity, and copious active sites, the obtained catalyst exhibited exceptional alkaline HER activity requiring a low overpotential of 23.6 mV at −10 mA/cm2, surpassing the state-of-the-art Pt. Additionally, a full electrolyzer required a cell voltage of 1.42/1.4 V at 10 mA/cm2 in alkaline water/seawater with promising stability. This work highlights a design principle for advanced HER catalysts and beyond.

Single-atom-catalysts (SACs) afford a fascinating activity with respect to other nanomaterials for hydrogen evolution reaction (HER), yet the simplicity of single-atom center limits its further modification and utilization. Obtaining bimetallic single-atom-dimer (SAD) structures can reform the electronic structure of SACs with added atomic-level synergistic effect, further improving HER kinetics beyond SACs. However, the synthesis and identification of such SAD structure remains conceptually challenging. Herein, systematic first-principle screening reveals that the synergistic interaction at the NiCo-SAD atomic interface can upshift the d-band center, thereby, facilitate rapid water-dissociation and optimal proton adsorption, accelerating alkaline/acidic HER kinetics. Inspired by theoretical predictions, we develop a facile strategy to obtain NiCo-SAD on N-doped carbon (NiCo-SAD-NC) via in-situ trapping of metal ions followed by pyrolysis with precisely controlled N-moieties. X-ray absorption spectroscopy indicates the emergence of Ni-Co coordination at the atomic-level. The obtained NiCo-SAD-NC exhibits exceptional pH-universal HER-activity, demanding only 54.7 and 61 mV overpotentials at −10 mA cm−2 in acidic and alkaline media, respectively. This work provides a facile synthetic strategy for SAD catalysts and sheds light on the fundamentals of structure-activity relationships for future applications.

The exact understanding for each promotional role of cation and anion vacancies in bifunctional water splitting activity will assist in the development of an efficient activation strategy of inert catalysts. Herein, systematic first-principles computations demonstrate that the synergy of anion-oxygen and cation-manganese vacancies (V O and V Mn ) in manganese dioxide (MnO 2 ) nanosheets results in abnormal local lattice distortion and electronic modulation. Such alterations enrich the accessible active centers, increase conductivity, enhance the water dissociation step, and favor intermediate adsorption-desorption, consequently promoting HER and OER kinetics. As proof of concept, robust electrocatalysts, MnO 2 ultrathin nanosheets doped with dual vacancies (DV-MnO 2 ) are obtained via a maturely chemical strategy. Detailed characterizations confirm the cation vacancies-V Mn contribute to enhanced conductivity and anion vacancies-V O enrich the active centers with optimized local electronic configurations, consistent with the simulative predictions. As expected, DV-MnO 2 exhibits exceptional bifunctionality with the strong assistance of synergetic dual vacancies which act as abundant "hot spots" for active multiple intermediates. Leading to a lower cell voltage (1.55 V) in alkali electrolyte is required to reach 10 mA cm −2 for the overall water splitting system. These atomic-level insights on synergetic DV can favor the development of activating strategy from inert electrocatalysts.

binary transition metal dichalcogenides (TMDs), [6][7][8] cubic pyrite phase, [9][10][11] and transition metal phosphides [12][13][14] have been conducted as viable alternatives to Pt. Moreover, several approaches such as engineering the nanostructure (nanowires, [15] nanosheets, [16] and nanoparticles [17] ), hybridization with carbon materials, [18][19][20] and introduction of heteroatoms into the crystal lattice [21][22][23] have been employed to achieve high energetic efficiency electrocatalysts. Unfortunately, most of the current state-of-the-art catalysts show inferior efficiency to Pt as a result of insufficiently reactive active sites, poor electrical conductivity, and inefficient electrical contact to the catalyst. [19,20,24] In the past decade, considerable efforts have been dedicated to maximize the number of exposed active sites, facile charge transport, and optimize the hydrogen adsorption energy, which are key factors that primarily contribute to the HER activity. Recent work has been discovered that the HER activity of TMDs can be remarkably enhanced by anion or cation substitution. [24][25][26][27][28][29][30] In this context, cationic substitution in the cubic pyrite phase, such as Ni:CoS 2 , Co:FeS 2 , Mn:CoSe 2 , and Fe:NiS 2 , has emerged as very attractive HER catalyst materials due to their abundant edge active site and optimizes the kinetic energy barrier of H atom adsorption, thus significantly improving the HER. [26][27][28][29] Alternatively, the substitution of chalcogenide anion atoms by Se, N, and P is another promising strategy to enhance the HER catalytic activity. [25,[30][31][32] Notably, the ternary pyrite-type cobalt phosphosulphide exhibits superior activity and durability toward electrocatalytic HER. [2,33] Until now, many works have shown that the hydrogen evolution reaction (HER) performance can be improved by anion or cation substitution into the crystal lattice of pyrite-structure materials. However, the synergistic effects of anion-cation double substitution for overall enhancement of the catalytic activity remains questionable. Here, the simultaneous incorporation of vanadium and phosphorus into the CoS 2 moiety for preparing 3D mesoporous cubic pyrite-metal Co 1-x V x SP is presented. It is demonstrated that the higher catalytic activity of CoS 2 after V incorporation can be primarily attributed to abundance active sites, whereas P substitution is responsible for improving HER kinetics and intrinsic catalyst. Interestingly, due to the synergistic effect of P-V double substitution, the 3D Co 1-x V x SP shows superior electrocatalysis toward the HER with a very small overpotential of 55 mV at 10 mA cm -2 , a small Tafel slope of 50 mV dec -1 , and a high turnover frequency of 0.45 H 2 s -1 at 10 mA cm -2 , which is very close to commercial 20% Pt/C. Density functional theory calculation reveals that the superior catalytic activity of the 3D Co 1-x V x SP is contributed by the reduced kinetic energy barrier of rate-determining HER step as well as the promotion of the desor...

Using first-principles calculations, we investigate the interactions between a WS2 monolayer and several gas molecules (CO, H2O, NO, and O2). Different sets of calculations are performed based on generalized-gradient approximations (GGAs) and GGA + U ([Formula: see text] eV) calculations with D2 dispersion corrections. In general, GGA and GGA + U establish good consistency with each other in terms of absorption stability and band gap estimations. Van der Waals density functional (vdW-DF) calculations are also performed to validate long-range gas molecule-WS2 monolayer interactions, and the resultant absorption energies of four gas-absorption cases (from 0.21 to 0.25 eV) are significantly larger than those obtained from calculations using empirical D2 corrections (from 0.11 to 0.19 eV). The reported absorption energies clearly indicate van der Waals interactions between the WS2 monolayer and gas molecules. The NO and O2 absorptions are shown to narrow the band gaps of the WS2 material to 0.75-0.95 eV and produce small magnetic moments (0.71 μB and 1.62 μB, respectively). Moreover, these two gas molecules also possess good charge transferability to WS2. This observation is important for NO- and O2-sensing applications on the WS2 surface. Interestingly, WS2 can also activate the dissociation of O2 with an estimated barrier of 2.23 eV.

Single-atom-catalysts (SACs) have recently gained significant attention in energy conversion/storage application, while the low-loading amount due to their easy-to-migrate tendency poses a major bottleneck. For energy-saving H2 generation, replacing sluggish...

Recently, many research studies have been focused on anion or cation substitution into the lattice of pyrite-type cobalt disulfide (CoS 2 ) for enhancing the hydrogen evolution reaction (HER) performance. Nonetheless, finding the correct pair of anion−cation dual substitution with added synergistic effect for boosting pH-universal HER activity remains an ongoing challenge. Additionally, a generalized activity descriptor and the HER mechanism in alkaline media remain elusive. Herein, to elucidate the HER mechanism and obtain the suitable anion−cation pair, we investigated the codoping of metal cations (Ti/V/Cr/Mn/Fe) and phosphorus anions into the CoS 2 moiety. Our theoretical prediction revealed that Ti and P codoping into CoS 2 exhibits superior HER performance at both pH 0 and 14, which is ascribed to the weak hydrogen binding energy in acid and fast water dissociation kinetics in alkaline media, thereby promoting HER. Remarkably, a follow-up experiment confirmed that Ti-CoSP showed astonishing HER activity inducing low overpotentials of 44 and 132 mV at −10 mA cm −2 in acidic and alkaline media, respectively, with superior stability for 40 h.

A theoretical investigation of two-dimensional graphene-Cr-graphene intercalation nanostructures has been carried out using density functional theory (DFT) calculations. The intercalation nanostructures of interest are classified based on the atomic ratio of Cr with respect to C on two graphene layers, and we accordingly assign nomenclatures to the intercalation nanostructures as 1-4, 1-12, and 1-16 GMG. Binding energy analysis suggests that the 1-12 and 1-16 GMG structures are energetically stable, whereas the 1-4 GMG structure is unstable. When examining the 1-4 bilayer graphene-Cr (GGM) structure, we have found that it is energetically stable and nonmagnetic. On the other hand, all three GMG intercalation structures are found to be ferromagnetic, and the 1-16 GMG structure exhibits the highest total magnetization (2.00 μ B /cell), whereas the 1-12 GMG structure exhibits the lowest total magnetization (0.46 μ B /cell). Interplays between stability and magnetic properties of these three nanostructures are discussed from electronic structure analysis. It is found for the two stable nanostructures that the 2p z orbitals of graphene layers are aligned antiferromagnetically with respect to the Cr layer, thus causing negative contributions to total magnetic moments of two stable GMG nanostructures.