Surface Roughening of Nickel Cobalt Phosphide Nanowire Arrays/Ni Foam for Enhanced Hydrogen Evolution Activity

Development of earth-abundant, efficient, and stable electrocatalysts for hydrogen evolution reactions (HER) in alkaline or even neutral pH electrolyte is very important for hydrogen production from water splitting. Construction of bimetal phosphides via tuning the bonding strength to hydrogen and increasing effective active sites through nanostructuring and surface engineering should lead to high HER activity. Here, ternary NiCoP nanowires (NWs) decorated by homogeneous nanoparticles have been obtained on Ni foam for a highly efficient HER property via long-term cyclic voltammetric (CV) sweeping. The electron density transfer between the positively charged Ni and Co and negatively charged P atoms, one-dimensional electron transfer channel of the NWs, and abundant active sites supplied by the nanoparticles and NWs endow the catalyst with low overpotentials of 43 and 118 mV to achieve the respective current densities of 10 and 100 mA cm^–2 together with long durability for at least 33 h in 1 M KOH. A cycled anodic dissolution–redeposition mechanism is disclosed for the formation of the NiCoP nanoparticles during the CV sweeping process. Such a surface roughening method is found to be adaptable to enhance the HER property of other phosphides, including Ni₂P nanoplates/NF, NiCoP nanoparticles/NF, and CoP NW/NF

Loading Cd_0.5Zn_0.5S Quantum Dots onto Onion-Like Carbon Nanoparticles to Boost Photocatalytic Hydrogen Generation

Carbon dots (C dots, size < 10 nm) have been conventionally decorated onto semiconductor matrixes for photocatalytic H₂ evolution, but the efficiency is largely limited by the low loading ratio of the C dots on the photocatalyst. Here, we propose an inverse structure of Cd_0.5Zn_0.5S quantum dots (QDs) loaded onto the onionlike carbon (OLC) matrix for noble metal-free photocatalytic H₂ evolution. Cd_0.5Zn_0.5S QDs (6.9 nm) were uniformly distributed on an OLC (30 nm) matrix with both upconverted and downconverted photoluminescence property. Such an inverse structure allows the full optimization of the QD/OLC interfaces for effective energy transfer and charge separation, both of which contribute to efficient H₂ generation. An optimized H₂ generation rate of 2018 μmol/h/g (under the irradiation of visible light) and 58.6 μmol/h/g (under the irradiation of 550–900 nm light) was achieved in the Cd_0.5Zn_0.5S/OLC composite samples. The present work shows that using the OLC matrix in such a reverse construction is a promising strategy for noble metal-free solar hydrogen production