Hierarchical phosphorus-oxygen incorporated cobalt sulfide hollow micro/nano-reactor for highly-efficient electrocatalytic overall water splitting

Transition metal sulfides have always been the promising electrocatalysts for overall water splitting. The regulation of electronic structure and accessibility of active sites are helpful to further boost their electrochemical performance from the aspect of thermodynamics and kinetics, respectively. Herein, we put forward an advanced multi-ion regulation strategy coupled with the morphology management strategy to prepare high performance electrocatalyst with low overpotential and high solar-to-hydrogen STH efficiency. Therefore, a hierarchical nanosheets stacked phosphorus-oxygen incorporated cobalt sulfide (Co-OSP) hollow micro/nano-reactor was designed and synthesized. The experimental results and theoretical calculations indicate that reasonably modulated phosphorus and oxygen extent render the electrocatalyst with optimal conductivity, electron structure and adsorption/desorption behavior of intermediates. In addition, the finite element analysis (FEA) results show that the unique morphology endows the electrocatalyst with fast mass diffusion/transfer pathway and much more accessible active sites. As a consequence, the Co-OSP hollow sphere achieves excellent electrocatalytic water splitting performance with overpotentials as low as 175.3 and 132.7 mV for OER and HER in 1.0 M KOH alkaline solution, respectively. When applied in silicon-based photovoltaic-electrochemical (PV-EC) system, Co-OSP electrodes realizes as high as 9.8 % STH efficiency with cell voltage of 1.48 V. This work presents a potential application in electrocatalysis, lithium batteries, solar cells and other energy-related fields that require catalysts with large exposed surface area and controllable local electric fields. The facile preparation processes and abundant raw materials reserve could increase the commercial viability.