Search

In situ engineering highly active and ultrastable bi-functional electrocatalysts based on metal ions from transition metal alloys that are simultaneously suitable for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is one of the key unresolved challenges on the way to energy-efficient hydrogen fuel production by water splitting. One such novel catalyst based on polyhedron N-doped Ni-Co phosphide is burgeoned directly from the Ni-Co foam (N-NiCoP/NCF) using a facile and eco-friendly approach without involving heavy metal ions. The N-NiCoP/NCF catalyst exhibits superior activity in 1.0 M KOH for overall water splitting, evidenced by the low overpotentials of 78 mV for HER and 225 mV for OER at a current density of 10 mA cm-2. The excellent electrocatalytic activity of N-NiCoP is attributed to the increased Fermi level due to effective N-doping and the abundant exposed active crystal planes (311) of heterostructured Co2NiP4 phase. Importantly, the N-NiCoP/NCF catalyst shows ultra-stable electrocatalytic performance while retaining structural integrity in both HER and OER processes during continuous reactions for over 100 h. These results open new avenues for in situ engineering of transition-metal based electrocatalysts used for renewable energy generation.

Hydrogen, generated by electrocatalytic process, is one of the most promising sources of green and sustainable energy. Herein, we report a novel elctrocatalyst for hydrogen evolution reaction (HER) fabricated by doping Ni foam (NF) supported Ni2P nanosheets with Cu atoms. The Cu atoms effectively tune the structure and physicochemical properties of Ni2P, leading to the lower HER free energy, improved electrical conductivity, and high exposure of surface active sites. The optimized Ni1.8Cu0.2-P displays an excellent catalytic performance and stability, which is demonstrated by the low overpotentials of 78 (Tafel slope: 70 mV dec-1) and 245 mV to reach a current density of 10 and 100 mA cm-2 for the HER in 1.0 M KOH. The high electrocatalytic activity of Ni1.8Cu0.2-P is attributed to the increased Fermi level and the exposed active crystal plane (201). The H2 amount produced with a current density of 10 mA cm-2 is about 1.91 mmol h-1 cm-2, which is the highest value among the reported non-precious metal catalysts.

Transition metal selenides are highly promising for clean hydrogen energy generation by overall water electrolysis. Here we report a new approach wherein highly efficient and ultra-stable bifunctional electrocatalyst is developed by synergistic atmospheric-pressure plasma, hydrothermal and selenization treatments of bimetallic electrodes leading to multiphase Ni-Fe-selenide nanosheets (MNFSNs). The remarkable performance in water splitting is evidenced by the low overpotentials for delivering a current density of 10 and 300 mA cm−2 (j10 and j300), which are only 56 and 288 mV for HER, and 200 and 342 mV for OER, respectively, along with robust durability. Moreover, the current densities 10 and 100 mA cm-2 are achieved at low cell voltages of 1.46 and 1.60 V, thus outperforming most of the reported electrocatalysts in two-electrode alkaline water electrolyzers. Ab initio atomistic simulations identify the active catalytic sites formed by Ni atoms located at the heterointerfaces between the FeSe2 and NiSe2 phases.

Bi-functional electrocatalysts capable to simultaneously sustain hydrogen and oxygen evolution reactions (HER, OER) under industry-relevant conditions of hydrogen production by water electrolysis are highly desired. Here, we implement a new concept of plasma-enabled simultaneous N-P heteroatom doping to achieve the highly-competitive activity and stability of trimetallic Ni-V-Fe bi-functional electrocatalysts on a NiFe foam (N-NiVFeP/NFF), evidenced by the lower overpotentials for HER (79 mV) and OER (229 mV) to deliver a current density of 10 mA cm−2 (j10) in the 1.0 M KOH electrolyte. Meanwhile, the N-NiVFeP/NFF exhibits ultra-stable performances with a current density from 10 to 100 mA cm-2 for over 100 h. Specifically, the HER and OER performances are near to those of noble-metal based electrocatalysts in the high current density region (> j200), attributing to the rich active sites exposed on the formed heterointerfaces among Ni-V-Fe phospho-nitrides, the changed electronic structure, and increased conductivity with nitrogen doping.

Water electrolysis using non-precious transition metal-based electrocatalysts is one of the most promising ways for renewable hydrogen energy. Herein, we develop high-performance catalysts of trimetallic sulfide (Ni3S2-FeS-CoS) nanosheets decorated with bimetallic-nitroxide (NiCo(N,O)x) nanodots on a 3D NiFeCo foam by in situ fabrication with approaches of the dielectric barrier discharge (DBD) plasma and hydrothermal sulphurization. The resulting catalyst shows excellent electrocatalytic activity for overall water splitting in alkaline medium, with the overpotentials 82 m V for hydrogen evolution reaction (HER) and 170 m V for oxygen evolution reaction (OER) at a current density of 10 mA cm−2 (j10), which are very competitive to most recent non-noble-metal electrocatalysts. Specially, the nanodots help achieve ultra-stable electrocatalytic performance evidenced by negligible changes for the physico-chemical structure of catalyst after a harsh HER or OER test over 50 h. Our results offer a versatile approach for the development of next-generation electrocatalysts for hydrogen economy and other applications.