CoAl LDH in-situ derived CoAlP coupling with Ni2P form S-scheme heterojunction for efficient hydrogen evolution

Accelerating the separation and migration efficiency of photogenerated charge carriers and creating abundant active sites are the keys to the excellent H₂ production performance of photocatalysts. In this work, two strategies, the construction of S-scheme heterojunction and the introduction of active P species, were carried out based on polyhedral Ni-MOF-74 and layered CoAl LDH, in order to accelerate the separation and migration of electron-hole pairs as well as create rich active sites for more improved photocatalytic H₂ evolution performance. First, a delicate Ni-MOF-74/CoAl LDH S-scheme heterojunction was constructed, and then Ni-MOF-74/CoAl LDH was converted to CoAlP/Ni₂P S-scheme heterojunction. That is, the active P species was introduced based on the presence of S-scheme heterojunction. More importantly, Ni-MOF-74/CoAl LDH S-scheme heterojunction photocatalyst exhibits visible improvement in H₂ generation rate in comparison with single Ni-MOF-74 and CoAl LDH, which is attributed to the formation of S-scheme heterojunction undoubtedly. Further, CoAlP/Ni₂P S-scheme heterojunction shows more improved H₂ production performance than Ni-MOF-74/CoAl LDH, suggesting that P-modification is a high-efficiency means for enriching surface active sites and implementing the conversion of S-scheme heterojunction to S-scheme heterojunction.     

Phosphorus-Modified Amorphous High-Entropy CoFeNiCrMn Compound as High-Performance Electrocatalyst for Hydrazine-Assisted Water Electrolysis

Exploiting highly active and bifunctional catalysts for both hydrogen evolution reaction (HER) and hydrazine oxidation reaction (HzOR) is a prerequisite for the hydrogen acquisition. High-entropy materials have received widespread attention in catalysis, but the high-performance bifunctional electrodes are still lacking. Herein, a novel P-modified amorphous high-entropy CoFeNiCrMn compound is developed on nickel foam (NF) by one-step electrodeposition strategy. The achieved CoFeNiCrMnP/NF delivers remarkable HER and HzOR performance, where the overpotentials as low as 51 and 268 mV are realized at 100 mA cm⁻². The improved cell voltage of 91 mV is further demonstrated at 100 mA cm⁻² by assessing CoFeNiCrMnP/NF in the constructed hydrazine-assisted water electrolyser, which is almost 1.54 V lower than the HER||OER system. Experimental results confirm the important role of each element in regulating the bifuncational performance of high-entropy catalysts. The main influencing elements seem to be Fe and Ni for HER, while the P-modification and Cr metal may contribute a lot for HzOR. These synergistic advantages help to lower the energy barriers and improve the reaction kinetics, resulting in the excellent bifunctional activity of the CoFeNiCrMnP/NF. The work offers a feasible strategy to develop self-supporting electrode with high-entropy materials for overall water splitting.