Charge transfer modulated heterointerfaces for hydrogen production at all pH values

Abstract

We present an ingenious all-pH hydrogen evolution reaction (HER) active heterostructure where the electrochemical activity is governed by the interfacial electronic charge transfer. The intertwined heterostructure consists of NiV layered double hydroxide (LDH) wrapped around the phosphorus-rich CoP nanowires (NWs). The experimentally observed charge transfer is corroborated by the charge density difference (CDD) and Bader charge calculations where 0.13 |e| is transferred from NiV-LDH to the CoP surface. With a Ni : V ratio of 3 : 1, the NV-31-CP self-supported catalyst reaches −10 mA cm⁻² current density at −55, −93, and −311 mV vs. the reversible hydrogen electrode (RHE) in alkaline, acidic and neutral media, respectively. ∼20 ml h⁻¹ H₂ is produced both in alkaline and acidic media by applying −160 and −202 mV vs. RHE potential, respectively, along with ≥200 h operational stability in both the media at an industrially-relevant current density of −1 A cm⁻². In alkaline, acidic and neutral media, the mass activities are 59.7, 19.7, and 2.5 A g⁻¹ at −100 mV vs. RHE, respectively. Both water and H⋯OH adsorption is most favorable on the self-supported heterostructure because of the electron redistribution and the largest density of states (DOS) at the Fermi level, thereby providing a positive influence on its electronic mobility and the HER activity at all pH values.