A high‐performance transition‐metal phosphide electrocatalyst for converting solar energy into hydrogen at 19.6% STH efficiency

Abstract The construction of high‐efficiency and low‐cost non‐noble metal bifunctional electrocatalysts for water electrolysis is crucial for commercial large‐scale application of hydrogen energy. Here, we report a novel strategy with erbium‐doped NiCoP nanowire arrays in situ grown on conductive nickel foam (Er‐NiCoP/NF). Significantly, the developed electrode shows exceptional bifunctional catalytic activity, which only requires overpotentials of 46 and 225 mV to afford a current density of 10 mA cm−2 for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), respectively. Density functional theory calculations reveal that the appropriate Er incorporation into the NiCoP lattice can significantly modulate the electronic structure with the d‐band centers of Ni and Co atoms by shifting to lower energies with respect to the Fermi level, and optimize the Gibbs free energies of HER/OER intermediates, thereby accelerating water‐splitting kinetics. When assembled as a solar‐driven overall water‐splitting electrolyzer, the as‐prepared electrode shows a high and stable solar‐to‐hydrogen efficiency of 19.6%, indicating its potential for practical storage of intermittent energy

Interface engineering on amorphous/crystalline Hydroxides/Sulfides heterostructure nanoarrays for enhanced solar water splitting

Developing highly efficient and stable noble-metal-free electrocatalysts for water splitting is critical for producing clean and sustainable energy. Here, we design a hierarchical transition metal hydroxide/sulfide (NiFe(OH)x–Ni3S2/NF) electrode with dual heterointerface coexistence using a cation exchange-induced surface reconfiguration strategy. The electrode exhibits superior electrocatalytic activities, achieving low overpotentials of 55 mV for hydrogen evolution and 182 mV for oxygen evolution at 10 mA cm–2. Furthermore, the assembled two-electrode system requires voltages as low as 1.55 and 1.62 V to deliver industrially relevant current densities of 500 and 1000 mA cm–2, respectively, with excellent durability for over 200 h, which is comparable to commercial electrolysis. Theoretical calculations reveal that the hierarchical heterostructure increases the electronic delocalization of the Fe and Ni catalytic centers, lowering the energy barrier of the rate-limiting step and promoting O2 desorption. Finally, by implementing the catalysts in a solar-driven water electrolysis system, we demonstrate a record and durable solar-to-hydrogen (STH) conversion efficiency of up to 20.05%. This work provides a promising strategy for developing low-cost and high-efficiency bifunctional catalysts for a large-scale solar-to-hydrogen generation

The ideal doping concentration of silicon wafer for single junction hybrid n-Si /PEDOT: PSS solar cells with 3.2% elevated PCE and V-oc of 620 mV

Increasing the open circuit voltage of organic/Si-based hetero-junction solar cells (HSCs) is an efficient path for improving its photoelectric conversion efficiency (PCE). Commonly, increasing the doping concentration (N-D) for silicon planar substrate could enhance the open circuit voltage (V-oc). Comparing with other groups used 10(15) cm(-3) and other various doping level, the selected 10(17) cm(-3) doping concentration, as the ideal doping level, could enhance 100 mV for V-oc and maximum increase the PCE up to 12.54% without any additional antireflection (AR) layer deposition. To our knowledge, this obtained V-oc of 620 mV is a prominent reported value for n-Si/PEDOT: PSS solar devices without any additional antireflection (AR) layer deposition. Meanwhile, this research work clarifies that the PCE is inconsistently increased with the doping concentration, and 10(18) cm(-3) or higher doping concentration would import internal defects and reduce the PEC. This investigation of silicon wafer's optimal doping level paves a utility way for easily enhancing the efficiency of industrialized Si/PEDOT: PSS solar cells with low-cost fabrication technologies

The Degradation Kinetics Study of Aromatic Organics with Different Functional Compounds on Anatase 001 Surface

Anatase TiO2 photocatalysts with exposed (001) facets have attracted great attention for environmental protection technology due to their high reactivity for degradation of organic species. In this work, potassium hydrogen phthalate (denoted as KHP), as the most commonly used reference standard solution for calibrating photoelectrochemical chemical oxygen demand (denoted as PeCOD) instrument, was selected as the study sample. The intrinsic degradation kinetics of KHP on (001) surface was investigated by a photoelectrochemical (denoted as PEC) method with a purposely (001) faceted double-layered structure TiO2 photoanode. The high kinetics constants of fast process of KHP and other acids indicate that the (001) surface possesses a higher reactivity of aromatic carboxylic acid as theoretically predicted. Meanwhile, the investigation of the KHP adsorption properties on A001 photoanode provides the possibility of using this photoanode as a sensor in a new type of PeCOD instrument for organic acid determination

Planar Organic-Si Hybrid Solar Cell with MoO(x)Mixed PEDOT:PSS as Hole Injection Layer Profits from Mo(5+)and Mo(6+)Synergistic Effects

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole injection layer plays an important role in planar Si/PEDOT:PSS heterojunction solar cells (HSCs). Herein, a MoO(x)mixed aqueous PEDOT:PSS cosolvent is developed and is applied into a Si/PEDOT:PSS solar cell preparation via a time-saving one-step spin-coating method. With an optimal concentration of MoO(x)dopants, the power conversion efficiency of the device exhibits from 10.26% up to 13.82% with all inherent photovoltaic parameters enhanced. The detailed characterization and analytical results indicate that an advanced electronic property is produced by MoO(x)dopants and interface optimization caused by synergistic effects from Mo(5+)and Mo(6+)species with PEDOT:PSS, which enhances its interface work function and promotes hole transportation capacity. The result paves a path for exploring efficient Si/PEDOT:PSS HSCs with suitable functional material and a simple solution-processable method

3D Melamine Sponge-Derived Cobalt Nanoparticle-Embedded N-Doped Carbon Nanocages as Efficient Electrocatalysts for the Oxygen Reduction Reaction

The large-scale and controllable synthesis of novel N-doped three-dimensional (3D) carbon nanocage-decorated carbon skeleton sponges (Co-NCMS) is introduced. These Co-NCMS were highly active and durable non-noble metal catalysts for the oxygen reduction reaction (ORR). This hybrid electrocatalyst showed high ORR activity with a diffusion-limiting current of 5.237 mA·cm-2 in 0.1 M KOH solution through the highly efficient 4e- pathway, which was superior to that of the Pt/C catalyst (4.99 mA·cm-2), and the ORR Tafel slope is ca. 67.7 mV·dec-1 at a high potential region, close to that of Pt/C. Furthermore, Co-NCMS exhibited good ORR activity in acidic media with an onset potential comparable to that of the Pt/C catalyst. Most importantly, the prepared catalyst showed much higher stability and better methanol tolerance in both alkaline and acidic solutions. The power density obtained in a proton exchange membrane fuel cell was as high as 0.37 W·cm-2 at 0.19 V compared with 0.45 W·cm-2 at 0.56 V for the Pt/C catalyst. In Co-NCMS, the N-doped carbon nanocages facilitated the diffusion of the reactant, maximizing the exposure of active sites on the surface and protecting the active metallic core from oxidation. This made Co-NCMS one of the best non-noble metal catalysts and potentially offers an alternative approach for the efficient utilization of active transition metals in electrocatalyst applications