Deciphering the Space Charge Effect of the p–n Junction between Copper Sulfides and Molybdenum Selenides for Efficient Water Electrolysis in a Wide pH Range

Abstract

Space charge transfer is crucial for an efficient electrocatalytic process, especially for narrow-band-gap metal sulfides/selenides. Herein, we designed and synthesized a core–shell structure which is an ultrathin MoSe2 nanosheet coated CuS hollow nanoboxes (CuS@MoSe2) to form an open p–n junction structure. The space charge effect in the p–n junction region will greatly improve electron mass transfer and conduction, and also have abundant active interfaces. It was used as a bifunctional electrocatalyst for water oxidation at a wide pH range. It exhibits a low overpotential of 49 mV for the HER and 236 mV for the OER at a current density of 10 mA·cm –2 in acidic pH, 72 mV for the HER and 219 mV at 10 mA·cm –2 for the OER in alkaline pH, and 62 mV for the HER and 230 mV at 10 mA·cm –2 for the OER under neutral conditions. The experimental results and density functional theory calculations testify that the p–n junction in CuS@MoSe2 designed and synthesized has a strong space charge region with a synergistic effect. The built-in field can boost the electron transport during the electrocatalytic process and can stabilize the charged active center of the p–n junction. This will be beneficial to improve the electrocatalytic performance. This work provides the understanding of semiconductor heterojunction applications and regulating the electronic structure of active sites.

Rational construction of loosely packed nickel nanoparticulates with residual HCOO ligands derived from a Ni-MOF for high-efficiency electrocatalytic overall water splitting

“…3 Electricity-driven water dissociation represents one of the most promising and appealing approaches for the manufacture of high-purity oxygen and hydrogen, deriving from the oxygen evolution reaction (OER) at the anode and hydrogen evolution reaction (HER) at the cathode. 4,5 Until now, the main obstacles restricting the wide commercial application of water electrolysis devices are the lack of highly active and low-cost electrocatalysts, which contribute to low overpotential requirements for both HER and OER processes. 6,7 As is known to all, precious metal (i.e., ruthenium, platinum, etc.)…”

Regulating the Active Sites of Metal–Phthalocyanine at the Molecular Level for Efficient Water Electrolysis: Double Deciphering of Electron‐Withdrawing Groups and Bimetallic

“…That meant the energy barrier of electron transport in the electrode‐electrolyte interface was reduced, the reaction kinetics resulted in enhanced. [ 25 ]…”

“…That meant the energy barrier of electron transport in the electrode-electrolyte interface was reduced, the reaction kinetics resulted in enhanced. [25] Furthermore, a two-electrode system with CuCoPc-F as the positive and negative electrode was established to illustrate its practicability in overall water splitting inspired by the wonderful OER and HER performance of CuCoPc-F electrocatalyst in alkaline solution. From Figure 4a,b, we can see the CuCoPc-F||CuCoPc-F electrode just required the lowest cell voltage of 1.51 V to achieve 10 mA cm −2 .…”

In situphosphoselenization induced heterointerface engineering endow NiSe2/Ni2P/FeSe2hollow nanocages with efficient water oxidation electrocatalysis performance

“…24 On the other hand, the heterointerface formed on the heterostructure layer is able to induce interface coupling interactions which not only improve electrical conductivity and facilitate charge transport but also optimize the adsorption of reaction intermediates in active centers. [25][26][27] Furthermore, the surface hydrophilic properties of the electrode material play a significant role in enhancing electrochemical activity. The superhydrophilic surface promotes the diffusion of electrolytes and reactants to the electrode surface, reducing contact resistance and accelerating the escape of gas bubbles.…”