Bifunctional Heterostructured Transition Metal Phosphides for Efficient Electrochemical Water Splitting

Abstract

Reducing green hydrogen production costs is essential for developing a hydrogen economy. Developing cost-effective electrocatalysts for water electrolysis is thus of great research interest. Among various material candidates, transition metal phosphides (TMP) have emerged as robust bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) due to their various phases and tunable electronic structure. Recently, heterostructured catalysts have exhibited significantly enhanced activities toward HER/OER. The enhancement can be attributed to the increased amount of accessible active sites, accelerated mass/charge transfer, and optimized adsorption of intermediates, which arise from the synergistic effects of the heterostructure. Herein, a comprehensive overview of the recent progress of bifunctional TMP-based heterostructure is introduced to provide an insight into their preparation and corresponding reaction mechanisms. It starts with summarizing general fundamental aspects of HER/OER and the synergistic effect of heterostructures for enhanced catalytic activity. Next, the innovational strategies to design and construct bifunctional TMP-based heterostructures with enhanced overall water splitting activity, as well as the related mechanisms, are discussed in detail. Finally, a summary and perspective for further opportunities and challenges are highlighted for the further development of bifunctional TMP-based heterostructures from the points of practical application and mechanistic studies.

Two-dimension on two-dimension growth: hierarchical Ni0.2Mo0.8N/Fe-doped Ni3N nanosheet array for overall water splitting

“…Nowadays, transition metal-based materials [19][20][21] including the chalcogenides, [22][23][24] phosphides, [25][26][27] nitrides, 28-30 carbides [31][32][33] and selenides [34][35][36] have been extensively applied for electrocatalysis. Among of these electrocatalysts, transition metal nitrides (TMNs) are the new emerging alternative electrocatalyst for water splitting due to the high electrical conductivity and corrosion-resistance.…”

Single‐Atom and Dual‐Atom Electrocatalysts Derived from Metal Organic Frameworks: Current Progress and Perspectives

“…OER plays a vital role in many electrochemical conversion devices such as water electrolyzer and rechargeable metal-air batteries. [86,87] In the OER process, the generated oxygen comes from the oxidation of hydroxyl or water molecules in the alkaline solution under acidic conditions and a series of oxygen adsorbates will generate, including HO*, O* and HOO*. This is a consequence of the transfer of electrons and protons, and the bonding interactions between these intermediates are crucial for catalytic activity.…”

Controlled Synthesis and Structure Engineering of Transition Metal‐based Nanomaterials for Oxygen and Hydrogen Electrocatalysis in Zinc‐Air Battery and Water‐Splitting Devices

“…where * represents active sites on the catalysts surface, and H* is the surface‐adsorbed hydrogen intermediate. The first step in HER is the Volmer reaction, where H + accepts an electron to form H* [20] . In acid conditions, H + comes from the hydronium ion, while in alkaline conditions, the water molecule is the hydrogen ion provider.…”

“…In practice, the energy difference always deviates from theoretical value; for example, most metal oxides need 3.2±0.2 eV to realize the transformation of HOO* → HO* [26] . As theoretical overpotential is determined by the step with the biggest energy barrier, it is crucial to design catalysts with optimized binding strength between intermediates and active sites [20,24a,27] …”