Effect of Mn substitution on the structure, properties and HER activity of cadmium phosphochlorides.

Cadmium phosphochlorides, CdPCl and CdPCl, possess cadmium atoms differently bonded to chlorine and phosphorus ligands. A combined experimental and theoretical study has been carried out to examine the effect of manganese substitution in place of cadmium in these compounds. Experimentally it is found that manganese prefers the CdPCl phase over CdPCl. First-principles calculations reveal, stabilization of CdPCl upon Mn-substitution with a significant reduction in the formation energy when Mn is substituted at Cd-sites coordinated octahedrally by Cl-ligands. Substitution of Mn at two different Cd-sites in these compounds not only alters their formation energy differently but also causes a notable change in the electronic structures. In contrast to n-type conductivity in pristine CdPCl, Mn substituted Cd Mn PCl analogues exhibit p-type conductivity with a remarkable enhancement in the photochemical HER activity and stability of the system. Photochemical properties of pristine and substituted compounds are explained by studying the nature of charge carriers and their dynamics.