Enriched Se vacancies engineering of RuSe2 induced by low-valence Cu doping for promoting hydrogen evolution and coupling power generation

Heteroatom doping and vacancy engineering play vital roles in designing a high-activity electrocatalyst. Herein, we proposed a novel enriched Se vacancies engineering of the promising ruthenium chalcogenide of RuSe2 induced by low-valence Cu doping for promoting hydrogen evolution reaction (HER) electrocatalysis in alkaline media. The Cu-doped RuSe2 with enriched Se vacancies supported on graphitized carbon (Cu-RuSe2@C) was synthesized by a simple one-step selenization of bimetallic MOF precursor of Ru/Cu-BTC (1,3,5-benzenetricarboxylic acid) polyhedra. Compared to the Cu(II)-dominant doped RuSe2 (CuII/I-RuSe2@C) with deficient Se vacancies, the proposed Cu(I)-dominant doped RuSe2 (CuI/II-RuSe2@C) with enriched Se vacancies exhibited significantly improved electrocatalytic activity, which was potentially derived from the created electron deficient Ru delta+ and Se nu-sites induced by low-valence Cu doping. Specifically, CuI/II-RuSe2@C needed only 40 mV overpotential to drive a HER current density of 10 mA cm-2, comparable to commercial Pt/C (38 mV) and much lower than those of CuII/I-RuSe2@C (93 mV) and RuSe2@C (362 mV). Furthermore, an alkaline Zn-H2O fuel cell with a CuI/II-RuSe2@C cathode was integrated to demonstrate its potential applications, which delivered a maximum power density of 15.1 mW cm-2 and specific capacitance of 660 mAh g-1 with good stability. Two series-connected alkaline Zn-H2O cells acted as a chemical energy converter for simultaneous electricity generation and hydrogen coproduction by driving the coupled water splitting.