In-situ single-phase derived NiCoP/CoP hetero-nanoparticles on aminated-carbon nanotubes as highly efficient pH-universal electrocatalysts for hydrogen evolution

Carbon Nanotube Support, Carbon Loricae and Oxygen Defect Co-Promoted Superior Activities and Excellent Durability of RuO2 Nanoparticles Towards the pH-Universal H2 Evolution

This work reports a strategy that integrates the carbon nanotube (CNT) supporting, ultrathin carbon coating and oxygen defect generation to fabricate the RuO2 based catalysts toward the pH-universal hydrogen evolution reaction (HER) with high efficiencies. Specifically, the CNT supported RuO2 nanoparticles with ultrathin carbon loricae and rich oxygen vacancies at the surface (C@OV-RuO2/CNTs-325) have been synthesized. The C@OV-RuO2/CNTs-325 shows superior activities and excellent durability for the HER. It only requires overpotentials of 36.1, 18.0, and 19.3 mV to deliver -10 mA cm-2 in the acidic, neutral, and alkaline media, respectively. Its HER activities are comparable to that of the Pt/C in the acidic media but higher than those of the Pt/C in the neutral and alkaline media. The C@OV-RuO2/CNTs-325 shows excellent HER durability with no activity losses for > 500 h in the acidic, neutral or alkaline media at -250 mA cm-2. The density-functional-theory calculations indicate that the CNT supporting, the carbon coating, and the OVs can modulate the d-band centers of Ru, increasing the HER activities of C@OV-RuO2/CNTs-325, and stabilize the Ru atoms in the catalyst, increasing the durability of the C@OV-RuO2/CNTs-325. More interestingly, the C@OV-RuO2/CNTs-325 shows great potential for practical applications toward overall seawater splitting.

An efficient cerium dioxide incorporated nickel cobalt phosphide complex as electrocatalyst for All-pH hydrogen evolution reaction and overall water splitting

Transition metal phosphides (TMPs) have been considered as potential electrocatalysts with adjustable valence states, metal characteristics, and phase diversity. However, it is necessary but remains a major challenge to obtain efficient and durable TMPs catalysts, which can realize efficiently for not only all-pH hydrogen evolution reaction (HER), but also oxygen evolution reaction (OER). Hence, cerium dioxide incorporated nickel cobalt phosphide growth on nickel foam (CeO2/NiCoP) is fabricated by hydrothermal and phosphating reaction. CeO2/NiCoP shows excellent activity for all-pH HER (overpotentials of 48, 58 and 72 mV in alkaline, neutral and acidic solution at the current density of 10 mA cm-2), and has a small OER overpotential (231 mV @ 10 mA cm-2). Moreover, the voltage of overall water splitting in alkaline solution and simulated seawater electrolyte is only 1.46 and 1.41 V (10 mA cm-2), respectively, coupled with outstanding operational stability and corrosion resistance. Further mechanism research shows that CeO2/NiCoP possesses rich heterointerfaces, which serves more exposed active sites and possesses a promising superhydrophilic and superaerophobic surface. Density functional theory calculations manifest that CeO2/NiCoP has appropriate energy for intermediates of reactions. This work provides a deep insight into the CeO2/NiCoP catalyst for high-performance water/seawater electrolysis.

Design of molybdenum phosphide @ nitrogen-doped nickel-cobalt phosphide heterostructures for boosting electrocatalytic overall water splitting

Transition metal phosphides (TMPs) are one of the most promising alternatives to noble metal electrocatalysts, but so far their activity and stability still fall short of expectations. Here, we prepare nitrogen-doped nickel-cobalt phosphide (N-NiCoP) and molybdenum phosphide (MoP) heterostructures engineered on nickel foam (NF) with nanosheet structure by high-temperature annealing and low-temperature phosphorylation. Notably, heteroatomic N doping and heterostructures construction are achieved together through a simple co-pyrolysis method. The distinctive composition can synergistically promote the electron transfer, lower the reaction barriers, thus improving the catalytic performance. Therefore, the modified MoP@N-NiCoP requires low overpotentials of 43 mV and 232 mV to reach 10 mA cm^-2 current density for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) accompanied by satisfactory stability in 1 M KOH. Density functional theory (DFT) calculations reveal the electron coupling and synergistic interfacial effects at the heterogeneous interface. This study provides a new strategy for heterogeneous electrocatalysts with elemental doping to promote hydrogen applications.