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A wide diversity of phosphides of platinum-group metal including Rh, Ru and Ir exhibit intriguing electrocatalytic activity toward hydrogen evolution reaction (HER). The phosphidation degree, namely the P dosage in these phosphides shows pronounced influence on the catalytic performance but is hard to control. In this work we developed a reliable strategy to synthesize Rh 2 P-based nanoparticles with controlled phosphidation degree, and investigated the influence of phosphidation degree on HER. It is found that the heterostructured Rh 2 P/Rh nanoparticle, i.e., the P-deficient composite with mixed metallic and phosphide phases, outperforms either the metallic Rh or pure Rh 2 P nanoparticles. As-synthesized Rh 2 P/Rh nanoparticles supported on P/N co-doped graphene (denoted as Rh 2 P/Rh-G) display remarkable HER activity with tiny overpotential of 17 and 19 mV at 10 mA cm−2 current density in alkaline and acid, efficiently surpassing its Rh-based rivals and benchmark Pt/C catalyst. Meanwhile it illustrates a large mass-specific activity (3.23 and 6.26 A mg−1 @50 mV overpotential in alkaline and acid, respectively) due to its high activity and low metal loading. Density functional theory (DFT) calculation indicates that the Rh 2 P/Rh heterostructured interface possesses the optimal close-to-zero value of hydrogen adsorption energy and water dissociation process is accelerated, and thus boosts HER activity. • Rh 2 P/Rh nanoparticles with controlled phosphidation degree were synthesized on graphene. • Rh 2 P/Rh-G displays remarkable HER activity and outperforms metallic Rh, pure Rh 2 P and Pt/C. • DFT calculation illustrates high activity of heterostructured Rh 2 P/Rh interface. [ABSTRACT FROM AUTHOR]

Electrochemical reduction of CO2 may provide a promising method to mitigate the concentration of CO2 in the atmosphere, and simultaneously convert this greenhouse gas into value‐added fuels or chemicals. However, electrocatalysts for CO2 reduction are mostly powder based; therefore, polymer binders are always employed to make these catalysts useful as working electrodes. As a consequence, plenty of active sites are embedded inside without catalytic performance, causing a relatively low efficiency. On the contrary, self‐supported electrocatalysts do not involve the typical powdering and drop‐coating procedure with the aid of polymer binders or additives, avoiding the weak contact between active materials and current collector. Moreover, the superior self‐supported structure can also provide an accelerated electron transfer, guarantee ample electrolyte access to the active sites, offer large electrochemical surface areas, and increase CO2 adsorption capacity around the active sites, finally leading to the excellent efficiency and long‐term stability in CO2 reduction. In this manuscript, recent advances regarding CO2 reduction by self‐supported electrocatalysts are comprehensively reviewed, including the synthesis methods, chemical compositions, nanostructures, and catalytic efficiencies. Furthermore, the existing challenges and perspectives on the research and development of self‐supported electrocatalysts for CO2 reduction are discussed. [ABSTRACT FROM AUTHOR]

Designing earth-abundant and highly active hydrogen evolution reactions (HER) electrocatalysts is pivotal for developing renewable energies. Here, we report that Mn-doped NiSe 2 nanosheets is successfully fabricated on carbon fiber cloth by solvothermal process and followed selenide reaction, showing excellent catalytic performance for electrochemical water splitting. Benefiting from the unique electronic property modified by Mn doping and nanosheets structures, the obtained electrodes only requires low overpotential of 86 mV to achieve the current density of 10 mA/cm2 in acid solution. Moreover, the higher normalized exchange current densities manifest that Mn doping can improve the intrinsic activity of NiSe 2. Furthermore, first-principle calculation results manifest that Mn doping can optimize the electronic structures to reduce hydrogen adsorption energy and consequently improve the HER active. This novel method is expected to provide new chances for developing efficient catalysts for energy conversion applications. • Mn–NiSe 2 nanosheets was synthesized by high temperature selenide reaction. • Mn–NiSe 2 nanosheets delivers superior catalytic activities for HER. • Mn dopants modify electronic structure and reduce hydrogen adsorption energy. [ABSTRACT FROM AUTHOR]

Developing stable and high-efficiency hydrogen generation electrocatalysts, particularly for the cathode hydrogen evolution reaction (HER), is an urgent challenge in energy conversion technologies. In this work, we have successfully synthesized Mn-doped NiP 2 nanosheets on carbon cloth (Mn-NiP 2 NSs/CC), which behaves as a higher efficient three dimensional HER electrocatalyst with better stability at all pH values than pure NiP 2 . Electrochemical tests demonstrate that the catalytic activity of NiP 2 is enhanced by Mn doping. In 0.5 M H 2 SO 4 , this Mn−NiP 2 NSs/CC catalyst drives 10 mA cm −2  at an overpotential of 69 mV, which is 20 mV smaller than pure NiP 2 . To achieve the same current density, it demands overpotentials of 97 and 107 mV in 1.0 M KOH and phosphate-buffered saline (PBS), respectively. Compared with pure NiP 2 , higher HER electrocatalytic performance for Mn−NiP 2 NSs/CC can be attributed to its lower thermo-neutral hydrogen adsorption free energy, which is supported by density functional theory calculations. [ABSTRACT FROM AUTHOR]

[Display omitted] • Identifying that the surface-supported electrocatalysts are actually not stable under harsh condition towards the practical applications. • A lattice-confined approach is developed to concurrently enhance the stability and intrinsic activity of Ru. • Lattice-confined Ru delivers both outstanding activity and stability for HER under harsh conditions. • Both experimental and theoretical results reveal that the lattice-confined strategy significantly enhances the interaction of Ru/TiO 2. Ru-based nanomaterials are among the best electrocatalysts for hydrogen evolution reaction (HER) in alkaline media, however their stability is still questionable, especially under harsh conditions towards practical applications (i.e., 80 °C, 6 M KOH). We demonstrate that the conventionally surface-supported Ru electrocatalysts are actually not stable under harsh conditions due to the weak interaction between Ru and supports, although they are stable under mild conditions. Here, we report a lattice-confined approach to concurrently enhance the stability and intrinsic activity of Ru via confining ultrafine Ru clusters into TiO 2 lattice frameworks. Impressively, such confined Ru delivers outstanding performance for HER under harsh conditions, such as a small overpotenital of 116 mV at 800 mA cm−2, and long-time stability for 200-h continuous HER at 300 mA cm−2. As uncovered by both computational and experimental results, the lattice-confined strategy can significantly enhance the interaction between Ru and TiO 2 for promoting the electron transfer from Ru to TiO 2 , thereby strongly stabilizing Ru for avoiding the dissociation and aggregation of Ru during the stability test. Therefore, the lattice-confined strategy may stand out as a robust approach for boosting the activity and stability of electrocatalysts. [ABSTRACT FROM AUTHOR]

Previous density‐functional theory (DFT) calculations show that sub‐nanometric Cu clusters (i.e. 13 atoms) favorably generate CH4 from the CO2 reduction reaction (CO2RR), but experimental evidence is lacking. Herein, a facile impregnation‐calcination route towards Cu clusters, having a diameter of about 1.0 nm with about 10 atoms, was developed by double confinement of carbon defects and micropores. These Cu clusters enable high selectivity for the CO2RR with a maximum Faraday efficiency of 81.7 % for CH4. Calculations and experimental results show that the Cu clusters enhance the adsorption of *H and *CO intermediates, thus promoting generation of CH4 rather than H2 and CO. The strong interactions between the Cu clusters and defective carbon optimize the electronic structure of the Cu clusters for selectivity and stability towards generation of CH4. Provided here is the first experimental evidence that sub‐nanometric Cu clusters facilitate the production of CH4 from the CO2RR. [ABSTRACT FROM AUTHOR]

Previous density‐functional theory (DFT) calculations show that sub‐nanometric Cu clusters (i.e. 13 atoms) favorably generate CH4 from the CO2 reduction reaction (CO2RR), but experimental evidence is lacking. Herein, a facile impregnation‐calcination route towards Cu clusters, having a diameter of about 1.0 nm with about 10 atoms, was developed by double confinement of carbon defects and micropores. These Cu clusters enable high selectivity for the CO2RR with a maximum Faraday efficiency of 81.7 % for CH4. Calculations and experimental results show that the Cu clusters enhance the adsorption of *H and *CO intermediates, thus promoting generation of CH4 rather than H2 and CO. The strong interactions between the Cu clusters and defective carbon optimize the electronic structure of the Cu clusters for selectivity and stability towards generation of CH4. Provided here is the first experimental evidence that sub‐nanometric Cu clusters facilitate the production of CH4 from the CO2RR. [ABSTRACT FROM AUTHOR]

Exploring highly-efficient and low-cost non-noble metal electrocatalyst toward the hydrogen evolution reaction (HER) is highly desired for renewable energy system but remains challenging. In this work, three dimensional hierarchical porous cobalt poly-phosphide hollow spheres (CoP 3 HSs) were prepared by topotactic phosphidation of the cobalt-based precursor via vacuum encapsulation technique. As a porous HER cathode, the CoP 3 HSs delivers remarkable electrocatalytic performance over the wide pH range. It needs overpotentials of −69 mV and −118 mV with a small Tafel slope of 51 mV dec −1 to obtain current densities of 10 mA cm −2 and 50 mA cm −2 , respectively, and maintains its electrocatalytic performance over 30 h in acidic solution. In addition, CoP 3 also exhibit superior electrocatalytic performance and stability under neutral and alkaline conditions for the HER. Both experimental measurements and density functional theory (DFT) calculations are performed to explore the mechanism behind the excellent HER performance. The results of our study make the porous CoP 3 HSs as a promising electrocatalyst for practical applications toward energy conversion system and present a new way for designing and fabricating HER electrodes through high degree of phosphorization and nano-porous architecture. [ABSTRACT FROM AUTHOR]

Developing high-efficiency, low-cost and non-precious metal electrocatalysts for future renewable energy conversion systems is highly desired. In this work, self-supported three-dimensional porous CoP 3 nanospheres on carbon cloth (CoP 3 NSs/CC) are fabricated via topotactic phosphidation of Co 3 O 4 NSs/CC. The synthesized CoP 3 NSs/CC, as a novel non-precious-metal electrocatalyst with large specific surface area and high porosity, exhibits efficient bifunctional electrocatalytic performance in alkaline medium, with Tafel slopes of 66 mV dec −1 and 72 mV dec −1 , and a current density of 10 mA cm −2 at overpotentials of −121 and 291 mV for HER and OER, respectively, which are remarkably superior to those of transition metal phosphides (TMPs). In addition, it just needs a cell voltage of 1.54 V to acquire a current density of 10 mA cm −2 for overall water splitting. The results of our work may shed light on the direction toward highly efficient bifunctional TMPs electrocatalysts with high phosphorous component. [ABSTRACT FROM AUTHOR]

Exploration of earth-abundant, low cost, and versatile catalysts with Pt-like performance for electrochemical water splitting holds practical significance for clean energy shortage and environmental pollution. However, manipulating the electronic structure and relevant physical properties of the catalysts is crucial in promoting their hydrogen evolution reaction (HER) performance but still a formidable challenge. In this work, we report a self-supported dual-metal doped on CoP3 nanowire arrays (NAs) and grown on carbon fiber cloth (Ni,Mn-CoP3 NAs) for alkaline HER. The optimized catalyst exhibits superior electrocatalytic activity, giving a low overpotential of 24 mV at 10 mA cm−2 with a small Tafel slope of 41 mV dec−1 and can sustain for 24 h, which is superior to the commercial Pt/C catalysts at a large current density. On the basis of systematic experiments and density functional theory calculations, the synergistic regulation of dual-metal doping can re-form the electronic structure so as to enhance the electrical conductivity, improve the intrinsic HER activity, and increase the electrochemical surface area of CoP3. This work points out avenues in the reasonable design and development of dual-metal doped transition-metal phosphides as highly active, durable, and economically viable catalysts for various catalytic reactions. [ABSTRACT FROM AUTHOR]

Herein, porous WP 2 nanosheet arrays integrated on graphite paper (P-WP 2 NSs/GP) as 3D flexible cathode for electrocatalytic hydrogen evolution reaction (HER) are prepared by in situ phosphidation via vacuum encapsulation assisted by pulsed laser deposition technique. Compared to the electrode without pre-deposition process, the enhanced catalytic activities are attributed to the increased effective catalyst loading and the reinforced charge transport kinetics. The results make the present P-WP 2 NSs/GP as a promising cathode for energy conversion and paves a new way for designing and fabricating efficient electrodes toward HER. [ABSTRACT FROM AUTHOR]

The design and development of high-efficiency and non-noble-metal hydrogen evolution reaction (HER) electrocatalysts for future clean and renewable energy system has excited significant research interests over the recent years. In this communication, the polymorphic tungsten diphosphide (p-WP 2 ) nanoparticles with mixed monoclinic (α-) and orthorhombic (β-) phases are synthesized by phase-controlled phosphidation route via vacuum capsulation and explored as a novel efficient electrocatalyst towards HER. The p-WP 2 catalyst delivers superior performance with excellent stability under both acidic and alkaline conditions over its single phases of α-WP 2 and β-WP 2 . This finding demonstrates that a highly efficient hybrid electrocatalyst can be achieved via precise composition controlling and may open up exciting opportunities for their practical applications toward energy conversion. [ABSTRACT FROM AUTHOR]

A significantly lower voltage was required in NiFe-MIL-53-NH 2 when using full urea electrolysis instead of overall water splitting. [Display omitted] • Incorporating Fe induces the formation of electrophilic Ni3+ and nucleophilic Fe3+. • The bimetallic NiFe-MIL-53-NH 2 presents excellent electrocatalytic UOR activity. • This work provides a new strategy to explore effective UOR electrocatalysts. Electrocatalytic urea oxidation reaction (UOR) presents lower thermodynamic potential than oxygen evolution reaction (OER), thus exhibiting promising potential to enhance the efficiency of overall water splitting. However, due to the intrinsically sluggish six-electron transfer process, the efficiency of UOR is still not satisfied. In response, we synthesized a bimetallic NiFe-MIL-53-NH 2 with superior activity toward UOR, which only needs a low potential of 1.398 V vs. RHE to obtain 50 mA cm−2 in 1.0 M KOH with 0.33 M urea, much lower than that in 1.0 M KOH (1.721 V vs. RHE). Furthermore, NiFe-MIL-53-NH 2 presents significantly more excellent UOR activity compared to its monometallic counterparts. The TOF value in NiFe-MIL-53-NH 2 (0.16 s−1) at 1.4 V vs. RHE is about 133- and 246-folds higher than that Ni-MIL-53-NH 2 (1.2 × 10-3 s−1) and Fe-MIL-53-NH 2 (6.5 × 10-4 s−1), respectively. XPS characterization discloses that the incorporation of Fe into Ni-MIL-53-NH 2 framework optimizes the local charge distribution of metal nodes, leading to the formation of electrophilic Ni3+ and nucleophilic Fe3+ species, which can absorb electron-donating –NH 2 and electron-withdrawing C = O groups in urea, respectively, and therefore result in excellent UOR. This simple strategy of regulating local charge distribution of active species by fabricating bimetallic MOFs provides a new strategy and direction to explore other highly efficient UOR electrocatalysts. [ABSTRACT FROM AUTHOR]